Comet Hyakutake , officially called C / 1996 B2 (Hyakutake), is a long-period comet discovered on January 30, 1996 by the Japanese amateur astronomer Yuji Hyakutake . In March 1996, the comet passed relatively close to the Earth (its approach was one of the closest approaches of comets to the Earth in the last 200 years). The comet was very bright and easily observed with the naked eye in the night sky, due to which it was named the " Big Comet of 1996" . For some time, comet Hyakutake eclipsed comet Hale - Bopp , which at that time was approaching the inner region Solar system .
The observation of Comet Hyakutake has led to several scientific discoveries. The most surprising for scientists was the first discovered X-ray emission from a comet, probably caused by the interaction of the ionized solar wind with neutral atoms in the comet's coma... In addition, the Ulysses spacecraft unexpectedly crossed the tail of comet Hyakutake at a distance of more than 500 million km from the nucleus .
Until the last passage of Comet Hyakutake through the solar system, its orbital period was 17,000 years, but after interacting with the gravitational field of the giant planets, it increased to 70,000 years or more.
Timeline
Opening
The comet was discovered on January 30, 1996 by the Japanese amateur astronomer Yuji Hyakutake . By that time, he had been searching for comets for several years, which largely determined his move to Kagoshima Prefecture for the darker sky of rural areas. His usual place of sighting was a mountain about 15 km from his home. To observe the starry sky, he used a powerful wide-angle astronomical binoculars with 6- inch objectives (150 mm ) Fujinon 25x150 MT-SX mounted on a mount .
This comet became the second in a row discovered by Hyakutake. He discovered the first, C / 1995 Y1on December 26, 1995 , but in the end it did not reach high brightness: it could only be observed through a telescope . Five weeks later, while observing C / 1995 Y1 and the surrounding space, he noticed another comet, just 4 ° from the part of the sky where he had previously found the first one . Recalling his condition at the time of the discovery of a new comet, Hyakutake wrote:
To be honest, I was a little confused. My reaction was somewhat difficult to understand, as I originally intended to travel [to my usual place] to take a picture of the first comet. I found the second comet in the same place as the first, near the constellations Libra and Hydra .
Hardly believing in his luck, Hyakutake announced the opening to the National Astronomical Observatory of Japan . On the same day, the discovery was confirmed by independent observers. At the time of detection, the comet was at a distance of about 2 AU. e. from the Sun , having an apparent magnitude of 11.0 and an angular diameter of 2.5-3 minutes . After its discovery, comet Hyakutake was found in the image taken on January 1, 1996 (that is, before it was discovered), when it was at a distance of 2.4 AU. e. from the Earth and had a brightness of 13.3 .
The first calculations of the comet's orbit, performed by the head of the Central Bureau of Astronomical Telegrams Brian Marsden on February 3 , showed that on March 25, 1996, the comet would pass approximately 0.1 AU. ie from the Earth . For comets, this is a very small distance: in the last century, only four "tailed wanderers" passed closer: C / 1983 H1 (IRAS - Araki - Alcoca) , 7P / Ponsa - Winnecke , 73P / Schwassmann - Wachmann and C / 1983 J1 (Sugano - Saigus - Fujikawa) .
At the beginning of 1996, bright comets had not appeared for almost 20 years: the last "Big" was Comet West (C / 1975 V1) . Since mid- 1995, astronomers have already anticipated the appearance of another comet, C / 1995 O1 (Hale-Bopp) , which was predicted to break this long "comet-free" period in 1997 . The discovery of comet Hyakutake gave reason to assume that it will outstrip Hale-Bopp and become the next in a series of bright comets, if only its activity continues .
Comets that first arrive in our system from the Oort cloud often "flash" brightly at first, but then their brilliance subsides as soon as their upper layer of volatiles evaporates. So, for example, it happened with the comet Kohoutek in 1973 : it was initially believed that it would be very bright, but the comet did not live up to the forecasts, reaching only moderate indicators . From the very beginning, orbital calculations showed that comet Hyakutake is not "new", but long-period : the last time it was in the solar system about 17,000 years ago, and it approached the Sun more than once ...These data indicated that the brightness of C / 1996 B2 would not change dramatically, and that the comet's appearance would be very memorable.
The passage of a comet past the Earth
By mid-February, the comet reached a brightness of 8.5 , and it became possible to observe it with small binoculars, and by the end of February, it could already be seen with the naked eye. Until mid-March, it was still not very noticeable, reaching only 4th magnitude and having a 5 ° tail. However, the closer the comet approached the Earth, the faster its brightness, coma diameter and tail length increased. So, if on March 13 the angular diameter of the C / 1996 B2 coma was estimated at 20 minutes, then on March 19 it exceeded 1 °, which is twice as large as the apparent diameter of the Moon . By March 24, thecomet had become one of the brightest objects in the night sky, and its tail was already 35 ° long. The comet was a remarkable bluish-green color.
On March 25, comet Hyakutake approached the Earth as close as possible (0.1018 AU = 15.2 million km) . The comet was moving so fast (about 50 km / s) that its movement could be seen in just a few minutes of observing the starry sky; in 30 minutes it covered a distance equal to the full diameter of the moon (0.5 °). Observers reported that its brightness is equal to 0th magnitude, and the length of the tail has grown to 80 ° (the absolute record for the apparent size of a comet's tail). Her coma , which by that time is almost at the zenith for observers of mid-northern latitudes , reached about 1.5-2 ° in diameter (that is, about 3-4 full diameters of the moon).Even with the naked eye, it was easy to see that the comet's head has a greenish color (a consequence of the strong emission of diatomic carbon C 2 ).
During the passage of the comet near the Earth, the inhabitants of the northern hemisphere had the opportunity to observe it all night, since, due to its large inclination, the visible trajectory of comet Hyakutake ran along the polar constellations . Such observation conditions are unusual for comets: the brightest comets of the 20th century were observed at twilight , and most of the other comets open near the Sun in the so-called "Everhart zone" .
Unlike other "Big" comets , in particular, the same comet Hale - Bopp , which appeared in the next 1997 , C / 1996 B2 became noticeable precisely because of its approach to the Earth, and not because of its size therefore, it was bright for only a few days. In addition, in some European countries (in particular, England) due to unfavorable weather conditions in March 1996, its observation was very difficult .
Perihelion and the path after it
After a close approach to the Earth, the comet's brightness dropped to 2nd magnitude, and stayed near this value near perihelion ( May 1, 1996 ), after which it continued to decline. In addition to the previously observed ionic tail, the comet has a dusty tail. True, now its proximity to the Sun made observation difficult. The study of the comet during its perihelion passage continued with the SOHO satellite , which at the same time recorded a large coronal mass ejection . The distance between the comet and the Sun at that time was 0.23 AU. ie
After passing the perihelion, comet Hyakutake quickly lost its brightness, and by the end of May it became inaccessible to the naked eye. Now the comet has moved to the southern hemisphere, but such extensive studies have not been carried out as before. The last known observation was made on November 2, 1996 .
Scientific results
Orbit
Comet Hyakutake's orbit has a number of features. In addition to the fact that the comet's trajectory allowed it to approach the Earth, another unusual fact was discovered: the comet's orbital plane has an inclination of 125 ° , that is, it is located almost perpendicular to the ecliptic plane . This fact, as well as the long period of the comet, indicate that it was formed in the Oort cloud , and not in the Kuiper belt .
The comet's original orbital period around the Sun was estimated at 17,000 years, but in 1996 the comet's orbit was heavily influenced by the gravity of the giant planets , and now estimates of the comet's return time range from 70,000 to 110,000 years. In this case, the point of maximum distance from the Sun ( aphelion ) is located at 4560 AU. e. (or 0.072 sv.g . )>.
The passage of a spacecraft through the tail of a comet
On May 1, 1996, an unexpected event occurred: the Ulysses research vehicle passed through the tail of comet Hyakutake . At this moment he was at a distance of 3.73 AU. e. from the Sun, and the angle of inclination to the ecliptic was about 45 °. No evidence of the meeting was found until 1998 . A group of astronomers studying archival data from Ulysses drew attention to a sharp increase in the level of protons , as well as changes in the strength and direction of the magnetic field around the spacecraft during flight . This meant that Ulysses crossed the trail of some object, it was assumed that comets.
In 2000, two independent groups of scientists began to find out what kind of object it was . The magnetic measurement group has been building on the fact that such changes in magnetic field are similar to phenomena thought to occur in comet ion tails. Finding no registered comets near Ulysses, the group expanded their search. She soon found out that on April 23, 1996, Hyakutake crossed the orbital plane of the device, being at a distance of 500 million km from it. Under the action of the solar wind at a speed of about 750 km / s, the tail displacement to the point of meeting with the spacecraft would take exactly 8 days.Based on Ulysses' data, it was also established that the source of the trace was in the plane of the orbit of comet Hyakutake .
At the same time, another group, working on data obtained from the Ulysses ion spectrometer, found a sharp jump in the ion level. The relatively high abundance of chemical elements meant that the source was definitely a comet . Thanks to the meeting with Ulysses, it was found that the length of the tail of this comet was at least 570 million km (3.8 AU). This is almost 2 times more than the previous record of 2 amu. e., belonging to the tail of the Big Comet in 1843 .
Composition
Observations made from Earth have revealed the presence of various compounds of hydrocarbons , nitrogen and sulfur , in particular, cyanide (HCN) and isocyanide (HNC) hydrogen, H CN, isocyanic acid (HNCO), carbon monoxide (CO), methyl alcohol ( CH 3 OH), formaldehyde (H 2 CO) , carbon monosulfide (CS), hydrogen sulfide (H 2 S) . For the first time organic gases were discovered for comets - ethane (C2 H 6 ) and methane (CH 4 ). Chemical analysis showed that the relative content of the latter was approximately equal. This indicates that the comet was born in interstellar space far from the Sun, whose radiation would have evaporated these volatile compounds . Comet Hyakutake's ice masses must have formed at temperatures of 20 K or less. Most likely, the medium “native” for the comet was denser than an ordinary interstellar cloud .
The deuterium content of the comet's ice was determined by spectroscopic methods . It was found that the D / H (deuterium to hydrogen ) ratio is approximately 3.0⋅10 , while in the oceans on Earth it is only 1.6⋅10 . There is a theory according to which the main source of water on Earth was comets that fell on the planet , but a similar higher D / H ratio found in comets Hyakutake, Hale-Bopp and Halley gives reason to doubt it ...
X-rays
One of the biggest surprises from Comet Hyakutake was very strong X-rays . It was recorded by the ROSAT apparatus on March 27, 1996 . This was the first time that comets had such radiation, but astronomers soon became convinced that almost every comet had it. The strongest radiation came from the comet's head on the "sunny" side.
It is assumed that the cause of this phenomenon is a combination of two processes. An important role is played by the interaction between charged particles of the solar wind and matter evaporating from the comet's nucleus . Although the phenomenon of reflection of solar X-rays has been observed in other space objects (for example, the Moon ), simple calculations show that, even with the highest reflectivity of a molecule or dust particle, it is impossible to explain such a strong radiation, whereas the "atmosphere" of a comet Hyakutake is rather thin and sparse. Observations of comet C / 1999 S4 (LINEAR)by the orbiting X-ray observatory " Chandra " in 2000 made it possible to establish that the main cause of X-ray radiation was the exchange of charges during the collision of highly active ions of carbon monoxide and nitrogen in the solar wind with neutral molecules of water , oxygen and hydrogen in a coma .
The comet nucleus and its activity
Radar observations at the Arecibo Observatory showed that the nucleus of comet Hyakutake was about 2 km across and was surrounded by a "swarm" of pebble- sized particles ejected at a speed of several meters per second. These measurements were confirmed by conclusions drawn from infrared and radio observations .
The small size of the nucleus (for comparison, the nucleus of Halley's comet is about 15 km across, the Hale-Bopp comet is about 40 km) with a high brightness of the comet itself means that the nucleus must be very active. Most comets release matter only in certain areas of their surface, but it seems that comet Hyakutake had all (or almost all) of the surface layer active. At the beginning of March, the dust release rate was 2 t / s, and as the comet approached perihelion, it increased 150 times. At the same time, the velocity of the ejection itself increased from 50 m / s to 500 m / s .
Observations of the ejection of matter allowed astronomers to establish the speed of rotation of the comet's nucleus. It was noted that, passing by the Earth, the comet ejected a large mass of matter with a period of 6.23 hours. A similar, but smaller eruption, occurring with the same frequency, confirmed that this was the rotation period of the comet's nucleus .
The legacy of the comet
After it became clear that Hyakutake would pass close to Earth, there were reports in some tabloids that the comet would actually hit Earth. The Weekly World News called the discovered comet a “doomsday comet”, confusing, however, almost all the details of its discovery. Nevertheless, the reaction of the masses to Hyakutake was still calmer than to the same Hale-Bopp a year later .
Comet Hyakutake is mentioned in some feature films. The main heroine of melodrama 2002 " A Walk to Remember " ( Engl. A Walk to the Remember ), removed Adam Shenkmanom , wanted to assemble a telescope to see the comet , is the desire to perform its young people closer to the end of the film . In one of the scenes of the film "Hurricane" by Leonardo Pieracchioni, members of the Quarini family are looking for a comet in the sky .
The comet was not ignored by astrologers either . So, she is mentioned in the book of Pavel Globa "The Teachings of the Ancient Aryans", where a chapter entitled "The Savior's Comet" is devoted to her .
In 1997, the studio Cyanogen Productions withdrew Comet yakutake documentary "the Comet Odyssey: the Comet Hyakutake Brought to Life with Time The Lapse Movies" .
Comet Heil-Bopp ( C / 1995 O1 ) is a long-period comet that has become, perhaps, the most "observed" comet of the 20th century , and one of the brightest in the past few decades. A record period of 18 months was visible to the naked eye, twice the previous record set by the Great Comet of 1811 .
It was discovered on July 23, 1995 at a very large distance from the Sun (about 7.2 AU ), suggesting that it will be quite bright when approaching the Earth. Despite the difficulty of predicting the brightness of comets to any degree of accuracy, this comet met and exceeded the expectations of astronomers, having passed the perihelion on April 1, 1997 . It is sometimes called the " Big Comet of 1997".
The appearance of Comet Hale-Bopp also caused confusion among humans, which has not been seen for a long time. It was rumored that an alienship was flying after the comet . The same rumors became the impetus for mass suicide among the followers of the new religious movement"Gates of Paradise" ...
Opening
The comet was discovered independently by two American observers - Alan Hale and Thomas Bopp . Hale spent many hundreds of fruitless hours searching for comets, and near his home in New Mexico, he was observing already known comets when, around midnight, he suddenly stumbled upon a hazy object measuring 10.5 near the globular cluster M70 in the constellation Sagittarius . Hale first determined that there were no other deep sky objects near this cluster.... Next, he discovered that the object was moving noticeably against the background of the stars (and therefore located in the solar system ), and wrote an email to the Central Bureau of Astronomical Telegrams , which tracks astronomical discoveries .
Bopp didn't have his own telescope . He was out in nature with his friends near Stanfield, Arizona , and was observing star clusters and galaxies when a speck of light flashed in the eyepiece of a friend's telescope. After checking the ephemeris of known objects in the solar system, Bopp realized that this speck was a new object, and sent a telegram to the same place where Hale was.
The next morning, the discovery of a new comet was confirmed, which was given the name of Comet Hale-Bopp and the designation C / 1995 O1. The discovery was announced in the circular No. 6187 of the International Astronomical Union . At the time of discovery, the comet was at a distance of 7.1 AU . e. the of Sun from .
Earlier images of the comet were soon discovered . So, Terence Dickinson found the comet in his picture taken on May 29, 1995, and Robert McNaught in the picture taken on April 27, 1993 , that is, two years before the discovery of the comet. At that time, its value was 18 , and the distance from the Sun was 13.0 AU. e.
The formation of the "Big Comet"
The comet became visible to the naked eye in May 1996 . Despite the fact that the increase in brightness is somewhat slowed down in the second half of the year , scientists optimistically predicted that the comet would be very bright. Due to its proximity to the Sun in December 1996, observations were difficult, but in January it became clearly visible again and was so bright that it could be seen even in the light of the lanterns of large cities .
Approaching the Sun, comet Hale - Bopp became brighter: in February it reached the 2nd magnitude , and it was already possible to distinguish its tails - a bluish ionic, directed in the direction opposite to the Sun, and a yellowish dusty hue, curved in the orbit of a comet. The solar eclipse in Eastern Siberia and Mongolia on March 9 made it possible to see the comet during the day . On March 23, 1997, comet Hale - Bopp approached the Earth at a minimum distance of 1.315 AU. e. (196.7 million km) .
On 1 April 1997, the comet was a stunning sight when it passed perihelion. With an average value of −0.7 it shone brighter than any star (excluding Sirius ), and its two tails stretched across the sky by 15-20 degrees (and parts invisible to a simple observer - by 30-40 °) ... The comet could be observed just after dusk; and although many "large" comets, passing perihelion, were not far from the Sun, comet Hale-Bopp could be observed in the northern hemisphere all night.
The development of the Internet at that time led to the emergence of many sites that tracked the details of the comet's flight and even published daily photographs . Thus, the Internet has played a large role in generating unprecedented public interest in the Hale-Bopp comet .
Comet Hale-Bopp could be even more impressive. If it had approached the same distance to Earth as in 1996 - comet Hyakutake (0.1 AU), it would have exceeded Venus in brightness , reaching −5th magnitude.
Removing a comet
After passing the perihelion, the comet moved to the southern celestial hemisphere, and its brightness began to weaken. The comet looked much less impressive to southern observers , but they were able to see how its brightness gradually faded during the second half of 1997. The last known naked eye observations of the comet date back to December 1997, so it has been visible for about 18 and a half months. This period broke the previous record of 9 months, set by the Great Comet of 1811 .
Now comet Hale-Bopp is receding, and its brightness continues to decrease. In August 2004, it flew out of the orbit of Uranus , and as of mid- 2008 it was at a distance of about 26.8 AU. e. from the sun. However, it is still being tracked by astronomers. The reason for this is the comet's unusually long activity. Recent observations (October 2007 ) indicate that the comet still has a coma with a brightness of about 20 . It is assumed that the reason for the unusually long activity lies in the slow cooling of the giant cometary nucleus .
It is expected that the comet will be available for observation with large telescopes until around 2020 , when its brightness drops to 30 . The comet will return to Earth around 4390. Comet Hale-Bopp is thought to have a 15% chance of becoming circumsolar in one of its next comebacks , and serving as the progenitor of a new family, such as the Kreutz family of comets .
Orbit changes
It is most likely that in the penultimate time the comet passed the perihelion about 4200 years ago . Its orbit is almost perpendicular to the plane of the ecliptic , so close approaches to planets are very rare for it. But in March 1996, the comet flew by at a distance of 0.77 AU . ie from Jupiter - close enough for the planet's gravity to affect its orbit . In this case, the point of the orbit ( aphelion ) farthest from the Sun approached from 600 to 350 AU. e. The comet's orbital period has decreased to 2400 years, and now her next appearance in the solar system is expected around 4390 ...
Scientific research
When approaching the sun, the comet was intensively studied by astronomers. In doing so, some important and interesting discoveries were made.
One of the most significant results was the discovery of a third type tail in the comet. In addition to the usual gas (ion) and dust tails, there was also a faint sodium tail , visible only with powerful instruments and a complex filter system . Sodium fluxes were previously noticed in other comets, but they did not form a tail in any of them. In Comet Hale - Bopp, it consisted of neutral atoms and stretched for almost 50 million kilometers in length .
The sodium source was inside the comet's head , although not in the core itself. There are several possible mechanisms for the formation of such a source, for example, collisions between dust particles surrounding the core, or "squeezing" sodium from these particles under the influence of ultraviolet radiation . It is not yet entirely clear which of the mechanisms manifested itself to a greater extent in this case.
While the dust tail simply remained behind the comet, describing its trajectory , and the ionic tail was directed directly from the Sun, the sodium tail ran between the two. This suggests that sodium atoms were pushed out of the comet's head under the pressure of light .
Excess deuterium
The comet was found to contain a high content of deuterium in the form of heavy water : almost twice as much as in Earth's oceans . This means that, although comet-Earth collisions could be an important source of water on the planet, they could not be the only source (if, of course, such a concentration is typical for all comets) .
The presence of deuterium in the composition of other hydrogen compounds was also discovered. The ratio of these elements varied in different structures, so astronomers assumed that the comet ices were formed not in the protoplanetary disk , but in the interstellar cloud . Of The models The ice Of Theoretical Formation's in nebulae show For the For That the Comet Hale - Formed of Bopp of the WAS the AT a temperature of 25-45 the the K .
Organic compounds
Spectroscopic observations of Comet Hale-Bopp revealed the presence of a group of organic compounds , some of which have never been found in comets. These complex molecules, such as acetic and formic acids and acetonitrile , could be in the core or formed during chemical reactions .
Argon detection
Comet Hale - Bopp was also the first comet to contain the noble gas argon . Noble gases are chemically inert and extremely volatile, with different gases having different boiling points . The latter property helps in tracking changes in the temperature of cometary ice. Thus, krypton evaporates at a temperature of 116-120 K, and it was found that its content in a comet is 25 times lower than in the sun ; on the contrary, the sublimation temperature of argon is 35–40 K, and its content is higher than that of the sun .
So it was established that the temperature of the inner ices of comet Hale - Bopp never exceeded 40 K, and at the same time at some point their temperature was higher than 20 K. Unless the formation of the solar system took place at temperatures lower than suggested in present, and at a higher initial argon content, the presence of argon in the comet means that comet Hale - Bopp formed beyond the orbit of Neptune somewhere in the Kuiper belt , and then moved to the Oort cloud .
Rotation
The comet's activity and gas emissions were not equally distributed over the entire surface of the nucleus, but manifested themselves in the form of strong emissions from certain points. By observing them, it became possible to calculate the rotation period of the comet's nucleus. It was found that the nucleus of comet Hale - Bopp does indeed rotate ; however, at different points in time, different values of the period were obtained: from up to superposition of rotations with several periods suggests that the comet's nucleus had more than one axis of rotation .
Another period (called the "super period"), calculated from dust emissions from the surface, turned out to be equal to 22 days. And in March 1997, it suddenly turned out that in the period from February to March, the comet changed its direction of rotation to the opposite. The exact reasons for this behavior remain a mystery, although it seems that it was due to strong non-periodic gas emissions .
Disputes about the satellite
In 1999, a work appeared, the author of which, in order to fully explain the observed nature of the dust release, suggested that the comet had a double nucleus. The work was based on theoretical research and did not refer to any direct observations of the secondary nucleus. It was stated, however, that it should have a diameter of 30 km, with a main core of 70 km, the distance between them is 180 km, and the period of mutual circulation is 3 days .
The provisions of this work were challenged by practical astronomers, who argued that even the high- resolution images of the comet taken by the Hubble telescope did not contain traces of a double core . In addition, in previously observed cases of comets with a double nucleus, they did not remain stable for long: the orbit of the secondary nucleus was easily disturbed by the gravity of the Sun and planets, tearing the comet apart.
With the help of adaptive optics in late 1997 - early 1998, a certain duality was shown in the glow of the nucleus of comet Hale - Bopp . True, it cannot be guaranteed that such an effect arises precisely because of the double nucleus.
Inexplicable
Since ancient times, comets are considered by many peoples to be a bad omen and are viewed with great suspicion. Perhaps due to the long approach to its perihelion, its unusual scope and activity, as well as statements of fears from the point of view of millennialism about the upcoming Y2K offensive - the year 2000, the comet has become the subject of many bizarre rumors and theories.
Alien ship
In November 1996 amateur astronomer Chuck Šrámek of Houston ( Texas , USA ) has made digital ( CCD ) a photograph of the comet, which could discern vague, slightly elongated object next to it. When a computer program was unable to identify such a star, Schramek called Art Bell's radio to report that he had found a "Saturn-like object" following the comet. UFO enthusiasts, in particular Cartney Brown, soon concluded that an alien spacecraft was flying behind the comet . Some experts in the astronomical community have stated that this object is nothing more thana star of 8.5 magnitude - SAO141894 - which did not appear in Shramek's computer program due to incorrect user settings . This fact is indeed confirmed, but half: there was a star nearby, but it was of a different magnitude. In addition, they stated that the light "rays" emanating from the object at an angle of 45 degrees were the result of light decomposition, and provided several images with a similar effect (although their images had 4 rays, not 2).
Later, Art Bell even stated that he had his own snapshot of the object - from an anonymous astrophysicist intending to confirm this discovery. But astronomers Oliver Heinot and David Tholen of the University of Hawaii responded that the photograph presented is a modified copy of their own image of the comet .
A few months later, in March 1997 , a religious cult calling itself the "Gate of Heaven"chose the appearance of a comet as a signal for mass cult suicide . They stated that they were leaving their earthly bodies to travel to the ship following the comet . 39 adherents cult suicides in Rancho Santa Fe...
The legacy of the comet
For almost everyone who saw it, Comet Hale-Bopp was just a beautiful and exciting element of the evening sky. The length of time available for observation, plus widespread coverage in the press and the Internet did their job: Comet Hale-Bopp made a strong impression on people, surpassing even Halley's comet in this respect in 1986 , and became, perhaps, the most " observed ", since was visible by more people than any previous appearance of Halley's comet. The comet broke many records: it was discovered at the farthest distance from the Sun (among the comets known at that time), had (possibly) the largest nucleus, and was observed 2 times longer than the previous record holder . It also remained brighter than zerostellar magnitude for 8 weeks .
Halley's comet is a bright short-period comet that returns to the Sun every 75-76 years . It is the first comet for which an elliptical orbit was determined and the frequency of returns was established. Named after the English astronomer Edmund Halley . The comet is associated with meteor showers eta-Aquarids and Orionids . Despite the fact that every centurymany brighter long-period comets appear, Halley's comet is the only short-period comet clearly visible to the naked eye . Since the earliest observations recorded in the historical sources of China and Babylon , at least 30 comet appearances have been noted. The first reliably identifiable sighting of Halley's comet dates back to 240 BC. e. The comet's last passage through perihelion was on February 9, 1986 in the constellation Aquarius ; the next is expected on July 28, 2061, followed by March 27, 2134 .
At the time of its appearance in 1986, Halley's comet became the first comet explored using spacecraft , including the Soviet vehicles Vega-1 and Vega-2 , which provided data on the structure of the cometary nucleus and the mechanisms of coma and tail formation comets ...
Discovery of Halley's comet
Halley's comet was the first comet with a proven periodicity. In European science, up to the Renaissance , the view of Aristotle dominated , who believed that comets are disturbances in the Earth's atmosphere . However, both before and after Aristotle, many ancient philosophers expressed very perspicacious hypotheses about the nature of comets. So, according to Aristotle himself, Hippocrates of Chios(5th century BC) and his student Aeschylus believed that “the tail does not belong to the comet itself, but it sometimes acquires it, wandering in space, because our visual ray, reflecting from the moisture entrained behind the comet, reaches the Sun ...The comet, unlike other stars, appears at very long intervals, because, they say, it lags [from the Sun] extremely slowly, so that when it reappears in the same place, it has already completed a full revolution. " In this statement, one can see a statement about the cosmic nature of comets, the periodicity of their movement, and even about the physical nature of the comet's tail, on which sunlight is scattered, and which, as modern studies have shown, is indeed largely composed of gaseous water. Seneca (I century AD) not only speaks of the cosmic origin of comets, but also offers a way of proving the periodicity of their motion, implemented by Halley: “It is necessary, however, that information about all previous comet occurrences be collected;for, because of the rarity of their appearance, it is still impossible to establish their orbits; find out if they are in order and if they appear exactly on their day in strict order. "
Aristotle's idea was refuted by Tycho Brahe , who showed that the 1577 comet had no parallax (by measuring the position of the comet in Denmark and Prague ). With its accurate measurements, this meant that it was at least four times farther than the Moon . However, uncertainty persisted as to whether comets revolved around the sun or simply flew along straight paths through the solar system .
In 1680-1681, 24-year-old Halley observed a bright comet ( C / 1680 V1 , often called Newton's comet), which first approached the Sun and then receded from it, which contradicted the concept of rectilinear motion. Investigating this question, Halley realized that the centripetal force acting on the comet from the direction of the Sun should decrease in inverse proportion to the square of the distance. In 1682, the year of the next appearance of the comet, which was later named after him, Halley turned to Robert Hooke with the question of which curve the body would move under the influence of such a force, but did not receive an answer, although Hooke hinted that he knew the answer.Halley went to Cambridge to Isaac Newton , who immediately replied that, according to his calculations, the movement will occur along an ellipse. Newton continued to work on the problem of the motion of bodies under the action of gravitational forces , refining and developing calculations, and at the end of 1684 sent Halley his treatise "The Motion of Bodies in Orbit" ( lat. De Motu Corporum in Gyrum ). The delighted Halley reported on Newton's results at a meeting of the Royal Society of London on December 10, 1684 and asked Newton for permission to print the treatise. Newton agreed and promised to send a sequel.In 1686, at the request of Halley, Newton sent the first two parts of his expanded treatise, entitled " Mathematical Principles of Natural Philosophy ", To the Royal Society of London, where Hooke caused a scandal by declaring his priority, but was not supported by his colleagues. In 1687, with a circulation of 120 copies of Halley's money, Newton's most famous treatise was printed. Thus, the interest in comets laid the foundations for modern mathematical physics . In his classic treatise, Newton formulated the laws of gravity and motion. However, his work on the theory of the motion of comets was not yet completed.Although he suspected that the two comets that were observed in 1680 and 1681 (and which piqued Halley's interest) were actually one comet before and after passing near the Sun, he was unable to fully describe its movement within his model. This was succeeded by his friend and publisher Halley, who in his 1705 work "Review of cometary astronomy" ( lat. Synopsis Astronomiae Cometicae ) used Newton's laws to account for the gravitational effects of Jupiter and Saturn on comets.
After studying the historical records, Halley compiled the first catalog of the orbital elements of comets and drew attention to the coincidence of the paths of comets 1531 (observed by Apian ), 1607 (observed by Kepler ) and 1682 . (which he himself observed), and suggested that this is the same comet orbiting the Sun with a period of 75-76 years. Based on the discovered period and taking into account the rough approximations of the impact of large planets, he predicted the return of this comet in 1758 .
Halley's prediction was confirmed, although the comet could not be detected until December 25, 1758, when it was noticed by a German peasant and amateur astronomer I. Palich . The comet passed through perihelion only on March 13, 1759, since the disturbances caused by the attraction of Jupiter and Saturn led to a delay of 618 days. Two months before the new appearance of the comet, this delay was predicted by A. Clairaud , who was assisted in the calculations by J. Lalande and Madame N.-R. Whisper . The calculation error was only 31 days.Halley did not live to see the return of the comet, he died in 1742 ... The confirmation of the comet return was the first demonstration that not only planets can revolve around the sun. This was the first successful confirmation of Newton's celestial mechanics and a clear demonstration of its predictive power. In honor of Halley, the comet was first named by the French astronomer N. Lacaille in 1759 .
Orbit parameters
The period of revolution of Halley's comet over the past three centuries ranged from 75 to 76 years, however, for the entire observation period from 240 BC. e. it varied over a wider range - from 74 to 79 years. Variations in period and orbital elements are associated with the gravitational influence of large planets, past which the comet flies. The comet revolves in a highly elongated elliptical orbit with an eccentricity of 0.967 (0 corresponds to an ideal circle , 1 to motion along a parabolic trajectory ). At its last return, the distance to the Sun at perihelion was equal to 0.587 AU . e. (between Mercury and Venus ) and distance in aphelion more than 35 a. e. (almost like Pluto ). The comet's orbit is inclined to the ecliptic plane by 162.5 ° (that is, unlike most bodies in the solar system , it moves in the direction opposite to the motion of the planets , and its orbit is inclined to the Earth's orbit by 180-162.5 = 17.5 °). This fact influenced the choice of the date and place of the encounter with the spacecraft comet during its return in 1986. The comet's perihelion is elevated above the plane of the ecliptic by 0.17 AU.e. Due to the large eccentricity of the orbit, the speed of Halley's comet in relation to the Earth is one of the greatest among all bodies in the solar system. In 1910, when flying past our planet, it was (254,016 km / h). Since the comet's orbit approaches the Earth's orbit at two points (see animated picture), dust generated by Halley's comet forms two meteor showers observed on Earth : the Eta-Aquarids in early May and the Orionids in late October.
Halley's comet is classified as a periodic or short-period comet , that is, one with an orbital period of less than 200 years. Comets with an orbital period of more than 200 years are called long-period . Short-period comets generally have a small orbital inclination to the ecliptic (about 10 degrees) and an orbital period of about 10 years, so the orbit of Halley's comet is somewhat atypical. Short-period comets with an orbital period of less than 20 years and an orbital inclination of 20-30 degrees or less are called the Jupiter family of comets ...Comets, the orbital period of revolution of which, like that of Halley's comet, is from 20 to 200 years, and the inclination of the orbit is from zero to more than 90 degrees, are called Halley-type comets. To date, only 54 Halley-type comets are known, while the number of identified comets of the Jupiter family is about 400.
It is assumed that Halley-type comets were originally long-period comets, whose orbits changed under the influence of the gravitational attraction of giant planets . If Halley's comet was previously a long-period comet, then it most likely comes from the Oort cloud - a sphere consisting of cometary bodies surrounding the Sun at a distance of 20,000-50,000 AU . e. At the same time, the Jupiter family of comets is believed to originate from the Kuiper belt - a flat disk of small bodies at a distance of between 30 AU from the Sun. e. (orbit of Neptune ) and 50 a. e. Another point of view on the origin of Halley-type comets was also proposed.In 2008, a new trans-Neptunian object was opened with a retrograde orbit similar to that of Halley's comet, which was designated . Its perihelion is located at a distance of 20 AU. e. from the Sun (corresponds to the distance to Uranus ), aphelion - at a distance of 70 AU . e. (exceeds twice the distance to Neptune). This object may be a member of a new family of small bodies in the solar system, which may serve as a source of Halley-type comets.
Numerical simulations show that Halley's comet is in its current orbit for 16,000 to 200,000 years, although accurate numerical integration of the orbit is impossible due to the appearance of instabilities associated with planetary disturbances over an interval of more than several tens of revolutions. The comet's motion is also significantly influenced by non-gravitational effects, since when approaching the Sun it emits jets of gas sublimated from the surface, leading to reactive recoil and a change in orbit. These orbital changes can cause perihelion travel time deviations of up to four days.
In 1989, Chirikov and Vecheslavov, having analyzed the results of calculations of 46 appearances of Halley's comet, showed that on large time scales the dynamics of the comet is chaotic and unpredictable. Moreover, on time scales of the order of hundreds of thousands and millions of years, the behavior of a comet can be described within the framework of the theory of dynamic chaos . The same approach makes it possible to obtain simple approximate estimates of the time of the nearest comet passages through perihelion.
The estimated lifetime of Halley's comet may be on the order of 10 million years. Recent studies show that it will evaporate or disintegrate into two in a few tens of millennia, or be thrown out of the solar system in a few hundred thousand years. Over the past 2000-3000 returns, the nucleus of Halley's comet has decreased in mass by 80-90%.
Calculations of past and future occurrences of Halley's comet
The history of research into the orbit of Halley's comet is inextricably linked with the development of computational methods in mathematics and celestial mechanics.
In 1705, Halley published parabolic orbital elements for 24 well-observed comets:
Collecting observations of comets from everywhere, I made a table - the fruit of extensive and tedious work - small, but not useless for astronomers.
He noticed the similarity of the orbits of comets in 1682 , 1607 and 1531 and published the first correct prediction of the comet's return.
Elements of the orbits of comets in 1531, 1607 and 1682, obtained by Halley
Passage of perihelion
Mood
Longitude of the node
Longitude of perihelion
Perihelion, a. e.
08/26/1531
162 ° 18 ′
50 ° 48 ′
301 ° 36 ′
0.58
10/27/1607
162 ° 58 ′
50 ° 21 ′
302 ° 16 ′
0.58
09/15/1682
162 ° 24 ′
49 ° 25 ′
301 ° 39 ′
0.57
Halley also identified the comet of 1456 with the same periodic comet , moving between the Earth and the Sun in a retrograde manner, although due to a lack of observations he could not determine the parameters of the orbit for this appearance. These identifications made it possible to predict the reappearance of the same comet in 1758, 76 years after the last appearance. The comet did return, and was discovered by Palich on Christmas Day on December 25, 1758. An even more accurate prediction of the time of this comet return was made by Clairaut.with assistants, who calculated the perturbation caused in the motion of the comet by Jupiter and Saturn (Uranus, Neptune and Pluto had not yet been discovered). He determined that the moment of passage through perihelion falls on April 13 with an estimated error of one month (the error was indeed a month, since the comet passed perihelion on March 12). Good predictions of the next return of 1835 were given by Damoiseo and Ponteculan , while the ephemeris was first calculated, that is, the future path of the comet among the stars, but most accurately, with an error of only 4 days, he predicted the return of the comet Rosenberger , for this he had to take into account the indignation newly discovered Uranus.The appearance of a comet in 1910, already accurately predicted by numerical integrationCowell and Crommelin .
Pingre ( 1783 - 1784 ) was able to confirm the identification of the comet in 1456 on the basis of additional observations discovered . Referring to the observations recorded in the Chinese chronicles, Pingre, among others, also calculated the approximate orbits of the great comet in 837 and the first comet in 1301, but did not recognize Halley's comet in both.
J.-B. Biot in 1843 , already knowing the average period of Halley's comet, putting it back in the past, tried to identify the previous appearance of Halley's comet among the recorded Chinese observations after 65 BC. e. In many cases, he proposed several possible candidates. Based on the similarity of the orbits, Biot was also able to identify the comet of 989 as Halley's comet. Using the Chinese data from Biot, Lager ( 1843 ) recognized Halley's comet in the autumn comet of 1378, comparing the apparent path of the comet in the sky calculated on the basis of known orbital elements with descriptions. In a similar way, he identified observations of Halley's comet in 760 ,451 and 1301 .
In 1850, J. Hind tried to find past appearances of Halley's comet in European and Chinese chronicles before 1301, like Biot, relying on an approximate return interval of about 76.5 years, but checking the correspondence of the observations to known orbital elements. Of his 18 identifications up to 11 BC. e. more than half ( 1223 , 912 , 837 , 603 , 373, and 11 BC ) were, however, wrong.
A conclusive connection between all appearances is possible only by tracing continuous changes in the comet's orbit under the influence of perturbations of the planets of the solar system in the past, as was done when predicting new appearances. This approach was first applied by Cowell and E. KD Crommelin (1907), using the approximate integration of the equation of motion backward in time, by varying the elements. Based on reliable observations from 1531 to 1910 , they assumed that the eccentricity of the orbit and its inclination remain constant, and the perihelion distance and longitude of the ascending node are continuously changing under the influence of disturbances.The first orders of the comet's period perturbations were calculated taking into account the action of Venus , Earth , Jupiter , Saturn , Uranus and Neptune . The motion of the comet was accurately traced to 1301 and with less accuracy to 239 BC. e. The error of their method in assessing the moment of passing through perihelion for the earliest appearance reached 1.5 years, and therefore they used the date May 15, 240 BC in the article. e., following from observations, and not from calculations.
The moments of the passage of Halley's comet through perihelion were further tried to calculate back from 451 AD. e. until 622 BC e. Russian astronomer MAVil'ev . Using the moments of the passage of Vilyev in the interval from 451 AD. e. until 622 BC e. and the results of Cowell and Krommelin for the period from 530 to 1910 , MM Kamensky picked up a Fourier interpolation series for orbital periods. While this formula was consistent with the data used to derive it, extrapolating it outside the original data domain is useless.As well as a similar analysis of Angstrom (1862) gave an error in predicting the passage through the perihelion in 1910 by 2.8 years, Kamensky's prediction of the next return ( 1986 ) was erroneous by nine months. Any attempts to find simple empirical formulas for determining past or predicting future comet appearances that do not take into account the dynamic model of the comet's motion under the influence of gravitational perturbations are meaningless.
On the eve of the reappearance of Halley's comet in 1986, studies of its past appearances were intensified:
In 1967, Joseph Brady and Edna Carpenter, based on 2000 observations of two previous appearances of Halley's comet, determined a preliminary orbit and calculated that the upcoming perihelion passage would be February 4, 1986 (the error caused by not taking into account gravitational reactive forces was about 4 days).
In 1971, the same authors, based on about 5000 telescopic observations of four previous appearances, were able to connect these four appearances by numerical integration, taking into account the non-gravitational forces in the form of a secular term, and predicted the time of the perihelion passage in 1986 with an error of about 1.5 hours. They also pioneered direct numerical integration to study the ancient appearance of Halley's comet, using the empirical secular term in the comet's equations of motion to account for non-gravitational effects. The comet's orbit, calculated from the last four appearances, was then numerically integrated back into the past until 87 BC. e.The times of passage through perihelion were in satisfactory agreement with the observational data given by Kiang in 1971 from 1682 to 218 ... However, further integration led to a noticeable discrepancy starting with the advent of 141. In 141, a real comet passed at a distance of 0.17 AU. That is, from the Earth and experienced a disturbance somewhat different from what was obtained in the calculations. Since the integration was not tied to observations earlier than 1682 , the slight difference between calculated and actual motion was exacerbated by a close pass near Earth in 141. In 1982, Brady refined these calculations.
In 1971, Tao Kiang, after re-analyzing all known European and Chinese past observations, used the method of varying elements to study the motion of Halley's comet from 1682 back to 240 BC. e. Taking into account the influence of perturbations of all planets on the orbital elements, Qiang was able to clarify the values of the moments of passage through the perihelion and confirmed the assumption that non-gravitational forces are responsible for slowing the average motion of the comet by a little more than 4 days in one orbital period. These non-gravitational forces are associated with the evaporation of cometary matter when passing near the Sun, accompanied by reactive recoil and a decrease in the mass of the nucleus.
In 1973, Brian Marsden , Zdenek Sekanina, and Donald Yemans developed a model of non-gravitational forces based on the reactive action of gases evaporating from the surface of a comet's nucleus.
In 1977, Emans used this model to successfully describe observations of the comet from 1607 to 1911 . The orbit based on observations in 1682 , 1759 and 1835-1836 was integrated back in time up to 837 . Due to the close approach of the comet to the Earth in 837 (minimum distance 0.04 AU ), they did not attempt to continue the calculations earlier than this time.
In 1981, Donald Emans and Tao Kiang, based on observations in 1759, 1682 and 1607, calculated the history of the motion of Halley's comet in the past up to 1404 BC by the method of numerical integration. e., introducing small empirical corrections, using very accurately determined from historical chronicles the times of the passage of perihelion in 837, 374 and 141. In addition, on the basis of observations in 837 in 800, an amendment was introduced to the eccentricity of the orbit.
In 1984 and 1986, Werner Landgraf, using the first observations of the new appearance, integrated the motion of the comet in the interval from 2317 BC. e. to 2284 AD e. and 467 BC e. to 2580 AD e. For calculations in the past, he used a single empirical correction equal to 0.03 days for the time of passage through perihelion in 837.
In 1988, Grzegorz Sitarski developed a method for the numerical integration of the motion of Halley's comet based on the best 300 observations from 1835 to 1987, uniformly using perihelion travel times for empirical corrections.
Although direct numerical integration is the only method to investigate the motion of Halley's comet beyond the reliable observation interval, an attempt must be made to link the integration with ancient observations. When the integration passes through the interval of strong perturbations caused by the close approach of the comet to the Earth and other large planets, special care is required in order to refine the calculated motion using the observational data. It was shown that, due to disturbances of major planets, the comet's orbit is not stable over long periods of time, and the initial uncertainties in determining the orbit grow exponentially with time when calculating to the past or to the future.
It is possible to get around this difficulty in moving into the past by making small corrections, relying on some of the most reliable and accurate observations. This does not allow, however, to determine with good accuracy the transit times, which are far from reliable observations.
Halley's comet appearances
Observations
Brady
Yemans, Kiang
Landgrave
Sitarsky
-
-
-
2134/03 / 28.66
-
-
-
2061/07 / 29.31
2061/07 / 28.86
-
1986/02 / 09.46
1986/02 / 09.39
1986/02 / 09.66
1986/02 / 09.51
-
1910/04 / 20.18
1910/04 / 19.68
1910/04 / 20.18
1910/04 / 20.18
-
1835/11 / 16.44
1835/11 / 15.94
1835/11 / 16.44
1835/11 / 16.44
-
1759/03/13.06
1759/03 / 12.55
1759/03/13.06
1759/03/13.06
1759/03 / 12.51
1682/09 / 15.28
1682/09 / 14.79
1682/09 / 15.28
1682/09 / 15.28
1682/09 / 14.48
1607/10 / 27.54
1607/10 / 26.80
1607/10 / 27.54
1607/10 / 27.52
1607/10 / 25.00
1531/08/25.80
1531/08 / 25.59
1531/08/26.23
1531/08 / 26.26
1531/08 / 23.68
1456/06 / 09.1
1456/06 / 08.97
1456/06 / 09.63
1456/06 / 09.50
1456/06 / 08.10
1378/11/09
1378/11 / 10.87
1378/11 / 10.69
1378/11 / 10.62
1378/11 / 09.64
1301/10 / 24.53
1301/10 / 26.40
1301/10 / 25.58
1301/10 / 25.19
1301/10 / 25.22
1222/10 / 0.8
1222/09 / 29.12
1222/09 / 28.82
1222/09 / 28.55
1222/09 / 29.68
1145/04/21.25
1145/04 / 17.86
1145/04 / 18.56
1145/04 / 18.12
1145/04 / 20.60
1066/03 / 23.5
1066/03 / 19.52
1066/03 / 20.93
1066/03 / 20.07
1066/03 / 22.68
989/09/08
989/09 / 02.99
989/09 / 05.69
989/09 / 04.09
989/09 / 07.69
912/07 / 9.5
912/07 / 16.59
912/07 / 18.67
912/07 / 17.00
912/07 / 19.28
837/02 / 28.27
837/02 / 27.88
837/02 / 28.27
837/02 / 28.48
837/02 / 28.31
760/05 / 22.5
760/05 / 21.78
760/05 / 20.67
760/05 / 20.61
760/05 / 20.53
684/09 / 28.5
684/10 / 6.73
684/10 / 02.77
684/10 / 01.43
684/10 / 02.47
607/03 / 12.5
607/03 / 18.20
607/03 / 15.48
607/03 / 13.57
607/03 / 15.04
530/09 / 26.7
530/09 / 26.89
530/09 / 27.13
530/09 / 25.63
530/09 / 27.31
451/06 / 24.5
451/06 / 25.79
451/06 / 28.25
451/06 / 27.23
451/06 / 27.96
374/02 / 17.4
374/02 / 12.56
374/02 / 16.34
374/02 / 15.29
374/02 / 15.35
295/04 / 20.5
295/04 / 22.54
295/04 / 20.40
295/04 / 20.63
295/04 / 20.02
218/05 / 17.5
218/05 / 27.56
218/05 / 17.72
218/05 / 17.71
218/05 / 17.76
141/03 / 22.35
141/04 / 10.24
141/03 / 22.43
141/03 / 21.08
141/03 / 22.53
66/01 / 26.5
66/02 / 19.97
66/01 / 25.96
66/01 / 21.90
66/01 / 25.57
−11 / 10 / 05.5
−11 / 10 / 08.64
−11 / 10 / 10.85
−11 / 10 / 06.00
−11 / 10 / 08.92
−86 / 08 / 02.5
−86 / 07 / 10.40
−86 / 08 / 06.46
−86 / 08 / 03.54
−86 / 08 / 03.41
−163 / 10 / 5.5
−163 / 06 / 22.38
−163 / 11 / 12.57
−163 / 10 / 30.11
−163 / 10 / 23.13
−239 / 03 / 30.5
−240 / 11 / 30.64
−239 / 05 / 25.12
−239 / 04 / 16.52
−239 / 03 / 22.55
-
−316 / 10 / 15.78
−314 / 09 / 08.52
−314 / 05 / 15.22
−314 / 02 / 13.31
-
−392 / 04 / 22.19
−390 / 09 / 14.37
−390 / 04 / 28.98
−391 / 12 / 15.22
−466?
−467 / 07 / 16.05
−465 / 07 / 18.24
−465 / 04 / 11.15
−466 / 12 / 2.00
-
−543 / 04 / 10.57
−539 / 05 / 10.83
—541 / 12 / 17.11
−542 / 04 / 13.94
−612?
−619 / 10 / 5.17
−615 / 07 / 28.50
—617 / 09 / 19.97
−619 / 10 / 16.14
Years BC e. in the table are indicated by astronomical count: 1 BC. e. = 0 year, 2 BC e. = −1 year, etc. The dates of the passage of perihelion for 1607 and later are given according to the Gregorian calendar , and all previous dates according to the Julian calendar .
Comet nucleus
The missions of the spacecraft Vega ( USSR ) and Giotto ( European Space Agency ) allowed scientists to learn for the first time about the surface structure of Halley's comet. Like all other comets, when approaching the Sun, low-boiling volatiles such as water , monoxide , carbon monoxide , methane , nitrogen and possibly other frozen gases begin to sublimate from the surface of its core . This process leads to the formation of a coma , which can be up to 100,000 km across.The evaporation of this dirty ice releases dust particles that are carried by gas from the core. Coma gas molecules absorb sunlight and then re-emit it at different wavelengths (this phenomenon is called fluorescence ), and dust particles scatter sunlight in different directions without changing the wavelength. Both of these processes lead to the fact that the coma becomes visible to the outside observer.
The action of solar radiation on a coma leads to the formation of a comet's tail. But even here, dust and gas behave differently. The ultraviolet radiation of the sun ionizes part of the gas molecules, and the pressure of the solar wind , which is a stream of charged particles emitted by the Sun, pushes the ions, pulling the coma into he comet's long tail , which can be more than 100 million kilometers long. Changes in the flow of the solar wind can even lead to observed rapid changes in the shape of the tail and even complete or partial breakage (this was observed, for example, in Halley's comet on June 6 and 7, 1910).Ions are accelerated by the solar wind to speeds of tens and hundreds of kilometers per second, much greater than the speed of the comet's orbital motion. Therefore, their movement is directed almost exactly in the direction from the Sun, as well as the type I tail they form. Ionic tails have a bluish glow due to fluorescence. The solar wind hardly acts on comet dust, it is pushed out of the coma by the pressure of sunlight ... Dust is accelerated by light much weaker than ions by the solar wind, therefore its movement is determined by the initial orbital speed of movement and acceleration under the influence of light pressure. The dust lags behind the ion tail and forms type II or III tails bent towards the orbit.Type II tails are formed by a uniform flow of dust from the surface. Type III tails are the result of a short-term release of a large dust cloud. Due to the spread of accelerations acquired by dust grains of different sizes under the action of the force of light pressure, the initial cloud also stretches into a tail, usually curved even more strongly than the type II tail. Dust tails glow with a diffused reddish light. Halley's comet had both Type I and Type II tails. A Type III tail was believed to have been observed in 1835. The 1986 photograph clearly shows the characteristically colored I (below) and Type II tails.
Despite the huge size of the coma, the nucleus of Halley's comet is relatively small and has an irregular potato shape measuring 15 × 8 × 8 km. Its mass is also relatively small, about 2.2⋅10 kg , with an average density of about (for comparison, the density of water is ), which probably means that the core consists of a large number of weakly bound fragments forming a pile of rubble ... Ground-based observations of the brightness of the coma show that the rotation period of Halley's comet is about 7.4 days, but images obtained by various spacecraft, as well as observations of the jets and the envelope indicate that the period is 52 hours and that the rotation is in the same direction as the revolution of the comet around the Sun. Since the comet's nucleus has an irregular shape, its rotation is also likely to be quite complex. Although detailed images of only about 25% of the surface of Halley's nucleus were obtained during space missions, they show an extremely complex topography with hills, troughs, ridges and at least one crater.
Halley's comet is the most active of all periodic comets. The activity of, for example, comet Encke or comet Holmes is one or two orders of magnitude weaker. The daytime side of Halley's comet (the side facing the Sun) is significantly more active than the night side. Investigations using spacecraft have shown that the gases emitted by the core are almost 80% water vapor, 17% carbon monoxide (carbon monoxide) and 3-4% carbon dioxide (carbon dioxide), with traces of methane . although more recent studies have shown only 10% carbon monoxide and also traces of methane and ammonia .It turned out that dust particles are mainly a mixture of carbon-hydrogen-oxygen-nitrogen (CHON) compounds, common outside The solar system , and silicates, which form the basis of terrestrial rocks. Dust particles are small, up to the limit of detection by devices (~ 1 nm). The ratio of deuterium and hydrogen in water vapor released from the surface of the nucleus was initially assumed to be similar to that observed in the World Ocean on Earth, which could mean that comets of the same type as Halley's comet could have provided the Earth with water in the distant past.However, subsequent observations showed that the content of deuterium in the cometary nucleus is much higher than in terrestrial water, which makes the hypothesis of the cometary origin of terrestrial water unlikely.
The Giotto spacecraft provided the first evidence to support Whipple 's hypothesis that comet nuclei are "dirty snowballs." Whipple hypothesized that comets are icy objects that heat up as they approach the Sun, which leads to the sublimation of ice (direct transformation of matter from a solid to a gaseous state) on the surface, while streams of volatiles scatter in all directions, forming a coma. Giotto showed that this model is generally correct, although it requires a number of amendments. For example albedo Halley's comet is only about 4%, which means that it reflects only 4% of the light incident on it. This little reflection would be expected from a lump of coal rather than a snowball.Therefore, despite the fact that Halley's comet appears dazzling white to observers from Earth, its core is actually coal-black. The surface temperature of the evaporating "black ice" should have varied from 170 K (-103 ° C) with a high albedo to 220 K (-53 ° C) with a low albedo, but measurements by the Vega-1 spacecraft showed that the surface temperature of Halley's comet is actually in the range of (+ 30 ... + 130 ° C). This suggests that only 10 percent of the core's surface is active, and that most of it is covered in a layer of dark dust that absorbs heat. All these observations indicate that Halley's comet is mainly composed of non-volatile materials, and therefore is more like a "lump of mud with snow" than "dirty snow".
Observation history
Observations of Halley's comet in antiquity
Halley's comet is the first known periodic comet. She has been observed at least 30 times. Information about its earliest appearance can be found in the historical chronicles of different peoples. Back in the Middle Ages, Europe and China began to compile catalogs of past observations of comets, which are called cometography. Cometography has proven to be very helpful in identifying periodic comets. The most complete contemporary catalog is Harry Kronk's fundamental five-volume Cometography, which can serve as a guide to the historical appearance of Halley's comet.
240 BC e. - The first reliable observation of a comet, its description is given in the work of the ancient Chinese historian Sima Qian " Shi Ji ".
In the seventh year (240), the comet appeared first in the east, then it was seen in the north, and in the fifth moon in the west. Warlord [Meng] Ao died ... The comet reappeared in the west. Xia-taihou died sixteen days later...
7th [year of the reign of Shi-Huangdi ]. A comet appeared in the north and then in the west. Xia-taihou passed away. Meng Ao died...
Original text (Chinese) [show]
Earlier evidence (the comet of the 78th Olympiad - 466 BC, described, in particular, by Pliny and Aristotle , appears in Chinese records; another comet was observed in 618 or 619 BC) cannot be uniquely identified with Halley's comet. However, it should be noted that generally before 240 BC. e. so far only 16 records of different comets have been found. In addition, the conditions for observing Halley's comet earlier than 315 BC. e. were unfavorable - it passed far from the Earth.
164 BC e. - In 1985, FR Stephenson published the data on observations of the comet that he discovered on the Babylonian tablets. On the Babylonian clay cuneiform tablets, in particular, are recorded the results of extensive centuries-old observations of the movement of planets and observations of other celestial events - comets, meteors , atmospheric phenomena . These are the so-called "astronomical diaries" covering the period from about 750 BC. e. to 70 AD e. Most of the "astronomical diaries" are now kept in the British Museum .
LBAT 380: A comet that previously appeared in the east on the path of Anu, in the Pleiades and Taurus regions, to the West [...] and followed the path of Ea.
LBAT 378: [… on the way] Ea in Sagittarius, one cubit ahead of Jupiter, three cubits higher to the north […]
These tables speak of the same event, and partially the data in them overlaps and is duplicated. Damage is shown in square brackets. The date and path of the comet in the sky are in very good agreement with theoretical calculations. On the same tablets, detailed data on the positions of the planets are given, which makes it possible to accurately determine that the month of the comet's passage began on October 21, 164 BC. e.
This comet may have played an important role in Middle Eastern history. In the third " Books of the Sibyls ", based on written around the middle of the 2nd century BC. e., it is reported about a comet in the west, which will be "a sign of the sword, hunger, death and fall of leaders and great people." And just at the end of 164 BC. e. there was the death of Ptolemy VII and unrest in the Ptolemaic empire and the death of Antiochus IV in the Seleucid empire . Perhaps this comet was reflected in the Bible , in the First andSecond books of the Maccabees and in chapters 9-12 of the Book of Daniel describing the events of this time. KD Blount suggests several indications of this appearance, in particular, in the Second Book of the Maccabees: "It happened that over the whole city for almost forty days there were in the air worn horsemen in golden robes and like warriors armed with spears .. . "
87 BC e. - On the Babylonian tablets, descriptions of the appearance of the comet on August 12, 87 BC were also found. e.
“13 (?) The interval between sunset and moonrise was measured at 8 degrees; in the first part of the night, a comet [... long skip due to damage] which is in IV month day after day, one unit […] between north and west, its tail is 4 units […] "
Although the description of the comet itself is damaged and therefore contains little astronomical information about the path, the positions of the planets later in the text also allow this appearance to be dated. This appearance could be reflected on the coins of the Armenian king Tigran the Great , whose crown is decorated with a “star with a curved tail”.
12 BC e. - A detailed description of the movement of a comet across the sky, indicating the dates and the closest to the trajectory of bright stars for almost two months, is contained in the "Treatise on the Five Phases" of the historical chronicle of the Chinese Han dynasty " Hanshu ", completed according to various sources at the end of the first - beginning of the second century BC ... e. A report on the observation of a comet for several days over Rome without specifying the dates is given by the historian of the III century Dion Cassius in the book "Roman History".
This comet could serve as a prototype for the star of Bethlehem .
66 year - Information about this appearance of a comet with an indication of its path in the sky was preserved only in the Chinese chronicle " Hou Hanshu ". However, sometimes he is associated with the message of Josephus Flavius in the book " The Jewish War " about the comet in the form of a sword, which preceded the destruction of Jerusalem.
141 years - This appearance is also reflected only in Chinese sources: in detail in " Hou Hanshu ", in less detail in some other chronicles.
218 year - The path of the comet is described in detail in the astronomical chapters of the chronicle " Hou Hanshu ". Probably, Dio Cassius connected with this comet the overthrow of the Roman emperor Macrinus .
295 - The comet is reported in the astronomical chapters of the Chinese dynastic stories The Book of Song and The Book of Chen .
374 AD - The appearance is described in the annals and astronomical chapters of the Book of Song and Book of Chen . The comet approached the Earth by only 0.09 AU . e.
451 AD - The appearance is described in several Chinese chronicles. In Europe, the comet was observed during the invasion of Attila and was perceived as a sign of the coming wars, described in the chronicles of Idatius and Isidore of Seville .
Halley's comet in the Middle Ages
530 AD - The appearance is described in detail in the Chinese dynastic " Book of Wei " and in a number of Byzantine chronicles. John Malala reports:
In the same reign ( Justinian I ), a large, terrifying star appeared in the west, from which a white ray went up and lightning was born. Some called it a torch. It shone for twenty days, and there was a drought, in the cities there were murders of citizens and many other terrible events
607 - The appearance is described in the Chinese chronicles and in the Italian chronicle of Paul the Deacon : "Then, also in April and May, a star appeared in the sky, which was called a comet." Although the Chinese texts give the path of the comet in the sky in accordance with modern astronomical calculations, confusion and discrepancy with the calculation of about a month are found in the reported dates, probably associated with errors of the chronicler. There is no such discrepancy for previous and subsequent appearances.
684 - This striking appearance sparked fear in Europe. According to the " Nuremberg Chronicle " Schedel this "tailed star" was responsible for the continuing for three months continuous rains that destroyed crops, accompanied by a strong lightning that killed a lot of people and livestock. The path of a comet in the sky is described in the astronomical chapters of the Chinese dynastic stories " The Book of Tang " and "The Initial History of the Tang ." There are also records of observations in Japan, Armenia (the source dates it to the first year of the rule of Ashot Bagratuni ) and Syria.
760 - Chinese Dynastic Chronicles The Book of Tang The Initial History of the Tang and The New Book of Tang give almost identical details about the comet's path that has been observed for over 50 days. The comet is reported in the Byzantine Chronography of Theophanes and in Arabic sources.
837 - During this appearance, Halley's comet approached the minimum distance to Earth for the entire time of observations (0.0342 AU ). The path and appearance of the comet are described in detail in the astronomical chapters of the Chinese dynastic stories " The Book of Tang " and "The New Book of Tang ". The length of the forked tail visible in the sky exceeded 80 ° at the maximum. The comet is also described in Japanese, Arab and many European chronicles. The interpretation of its appearance for the emperor of the Frankish state Louis I the Pious, as well as the description in the text of many other astronomical phenomena by the anonymous author of the work "The Life of the Emperor Louis" allowed historians to give the author the codename Astronomer .
912 - Descriptions of this appearance have been preserved in the sources of China (the most detailed), Japan, Byzantium, Russia (borrowed from Byzantine chronicles), Germany, Switzerland, Austria, France, England, Ireland, Egypt and Iraq. The 10th century Byzantine historian Simeon Logofet writes that the comet looked like a sword.
989 - The comet is described in detail in the astronomical chapters of the Chinese dynastic " history of the Song ", noted in Japan, Korea, Egypt, Byzantium and in many European chronicles, where the comet is often associated with the ensuing plague epidemic.
1066 - The comet approached the Earth at a distance of 0.1 AU . e. It was observed in China, Korea, Japan, Byzantium, Armenia, Egypt, in the Arab East and in Russia. In Europe, this appearance is one of the most mentioned in the chronicles. In England the appearance of the comet has been interpreted as an omen of impending death of King Edward the Confessor and the subsequent conquest of England by William I of . The comet is described in many English chronicles and depicted on the famous Bayeux carpet from the 11th century, depicting the events of that time.The comet may be depicted in a petroglyph located in Chaco National Park, in the US state of New Mexico .
1145 appearance of the comet is recorded in many chronicles of the West and East. In England, the Canterbury monk Edwin sketched a comet in the Psalter .
1222 - The comet was observed in September and October. It is noted in the chronicles of Korea, China and Japan, in many European monastic annals, in Syrian chronicles and in Russian annals. There is an assumption, not supported by historical evidence, but echoing the message in the Russian annals (see below), that Genghis Khan perceived this comet as a call to a march to the West.
1301 - A lot of European chronicles, including Russian chronicles, report about the comet. Impressed by the observation, Giotto di Bondone depicted the Star of Bethlehem in the form of a comet on the adoration of the Magi fresco in the Scrovegni Chapel Church in Padua ( 1305 ).
1378 - This appearance was not particularly remarkable due to unfavorable observation conditions near the Sun. The comet was observed by Chinese, Korean and Japanese court astronomers and possibly in Egypt. There is no information about this appearance in the European chronicles.
Halley's comet in the Russian annals
In the Russian annals, along with descriptions of many other astronomical phenomena, the appearance of Halley's comet is also noted. In Russia, a comet was observed in 1066, 1145, 1222, 1301, 1378, 1531, 1607, 1682, and also in the annals based on Byzantine chronicles, the appearance of a comet in 912 is reported. Also, after describing the comet in 1066:
In these times, there was a sign to the west, the stars are great, the rays of the possessions are bloody, rising from the evening to sunset and staying for 7 days. Behold, you show it not for good, because there are many strife, and the invasion of the rotten on the Russian land, this is a bloody star, showing blood shedding.
The Laurentian Chronicle reports even earlier comets, presumably the appearances of Halley's comet in 164 BC. BC 66 and 530:
We therefore understand, as though anciently, under Antios, in Jerusalem, it happened suddenly throughout the city in 40 days to appear on the swell on the horse-riders, in the arms, the clothes of the possessors of gold, and the regiments of wallpaper are shown, and the weapons are moving; Behold, the presence of Antiochus on Jerusalem is manifested. Seven, under Nero, the Caesars in the same Jerusalem, the stars were raised, on the image of a spear, over the city: behold, the presence of the host from the Romans was manifested. And the pack of sitsa was at Ustinyanѣs Caesars, the stars were rising to the westѣ, emitting rays, I'm calling it shine, and the days were shining 20.
Records of the observation of Halley's comet make it possible to clarify the dates of some events in Russian history. The appearance of the comet in 989 is not noted in the Russian chronicles, nevertheless, the comet of 989 is of great interest for Russian history precisely in connection with the attempt to establish the correct chronology of events associated with the Baptism of Rus and the capture of the Kiev prince Vladimir Korsun by the troops . Disputes about the interpretation of Byzantine and Eastern evidence about the comet and the pillars of fire accompanying the events described, when compared with the messages of the Russian chronicles and the life of Vladimir, which began more than a century ago, continue to this day.
The appearance of Halley's comet in 1222 AD e. preceded the Mongol-Tatar invasion ( battle on the Kalka River ). The Gustin Chronicle reports:
In this summer of the month of May, a terrible star appears, shining for 18 days, extending the ray to the east, and a new evil for the Christian, even two years later, created by the invasion of the enemy, there are godless Tatars, theirs is not ours in this country.
The chroniclers also associated the appearance of 1378 with an important stage of the Mongol-Tatar yoke . Commenting on the appearance of Halley's comet in 1531, the author of the Chronographic Chronicle writes: "The same was the sign under the Grand Duke Dmitry Ivanovich Donskoy , three years before the godless Taktamysh was found at the reigning city of Moscow." In earlier annals, records of the appearance of the comet in 1378 are not found, however , DO Svyatsky believes that the description fell into the story "On the capture and arrival of the Tsar Takhtamysh, and on the Moscow capture", standing in the Novgorod IV Chronicle and in many other chronicles in article 1382:
There was a certain manifestation, for many nights there was such a sign in heaven: in the east, before the early dawn, there was a certain star, like a tail, and, as if in a spear, when it was dawn in the evening, and when it was in matins, it also happened many times. This same sign manifests the evil coming of Takhtamyshevo to the Rus land, and the bitter, rotten Tatars are found on the peasants, as if they were by God, for the multiplication of our grains.
Astronomical observations of a comet in modern times
1456 - This appearance marks the beginning of astronomical studies of the comet. She was discovered in China on May 26. The most valuable observations of the comet were made by the Italian physician and astronomer Paolo Toscanelli , who accurately measured its coordinates almost every day from June 8 to July 8. Important observations were also made by the Austrian astronomer Georg Purbach , who was the first to attempt to measure the comet's parallax and found that the comet was at a distance of "more than a thousand German miles" from the observer. In 1468 an anonymous treatise "De Cometa" was written for PopePaul II , which also contains the results of observations and determination of the coordinates of the comet.
1531 - Peter Apian first noticed that the comet's tail is always oriented in the direction of the sun.
1607 - The comet was observed by Johannes Kepler , who decided that the comet was moving in a straight line through the solar system.
1682 Edmund Halley observed the comet . He discovered similarities in the orbits of comets in 1531, 1607, and 1682, suggested that it was one periodic comet, and predicted the next occurrence in 1758. This prediction was ridiculed in Gulliver's Travels by Jonathan Swift (published 1726-1727). Laputa scientists in this satirical novel fear that "a future comet, which, according to their calculations, is expected to appear in thirty-one years, in all likelihood, will destroy the earth ..."
1759 first predicted appearance of Halley's comet. The comet passed through perihelion on March 13, 1759, 32 days later than A. Clairaut's prediction. It was discovered on Christmas Day 1758 by amateur astronomer I. Palich . The comet was observed until mid-February 1759 in the evening, then disappeared against the background of the Sun, and from April it became visible in the early morning sky. The comet reached approximately zero magnitude and had a tail extending 25 °. Was visible to the naked eye until early June. The last astronomical observations of the comet were made at the end of June.
1835 - Since this appearance was predicted not only the date of the passage of Halley's comet perihelion, but also the ephemeris was calculated , astronomers began to search for the comet using telescopes from December 1834. Discovered Halley's comet as a weak point on August 6, 1835, the director of a small observatory in Rome, S. Dumouchel (Etienne Stefano Dumouchel). On August 20 in Dorpat it was rediscovered by V. Ya. Struve , who two days later was able to observe the comet with the naked eye. In October, the comet reached 1-st magnitude and had a tail about 20 ° long. V. Ya. Struve in Dorpat with the help of a large refractorand J. Herschel on an expedition to the Cape of Good Hope made many sketches of a comet that was constantly changing its appearance. Bessel , who also followed the comet, concluded that its motion was significantly influenced by the non-gravitational reactive forces of gases evaporating from the surface. On September 17, V. Ya. Struve observed the covering of a star by the head of a comet . Since no change in the brightness of the star was recorded, this allowed us to conclude that the matter of the head is extremely rarefied and that its central core is extremely small .The comet passed perihelion on November 16, 1835, just a day later than F. Ponteculan's prediction, which allowed him to clarify the mass of Jupiter, taking it equal to 1/1049 of the Sun's mass (the current value is 1 / 1047.6) ... J. Herschel followed the comet until May 19, 1836.
1910 - During this appearance, Halley's comet was first photographed and the first spectral data on its composition were obtained . The minimum distance from Earth was only 0.15 AU . e. , and the comet was a bright celestial phenomenon. The comet was discovered during the approach on September 11, 1909 on a photographic plate by M. Wolf in Heidelberg using a 72-cm reflector telescope equipped with a camera, in the form of an object of magnitude 16-17 ( exposure when photographing was 1 hour). An even fainter image was later found on a photographic plate obtained on August 28.The comet passed perihelion on April 20 (3 days after the predictions of FH Cowell and EKD Krommelin) and in early May was a bright sight in the predawn sky. At this time, Venus passed through the tail of the comet . On May 18, the comet found itself exactly between the Sun and the Earth, which also plunged into the comet's tail for several hours, which is always directed from the Sun. On the same day, May 18, the comet passed across the solar disk. Observations in Moscow were carried out by VK Tserasky and PK Sternberg using a refractor with a resolution of 0.2-0.3 ″, but could not distinguish the nuclei ...Since the comet was at a distance of 23 million km, this made it possible to estimate that its dimensions are less than . The same result was obtained from observations in Athens . The correctness of this estimate (the maximum size of the nucleus turned out to be about 15 km) was confirmed during the next appearance, when the nucleus was investigated at close range using spacecraft. In late May - early June 1910, the comet had 1st magnitude, and its tail had a length of about 30 °. After May 20, it began to move away quickly, but was photographed until June 16, 1911 (at a distance of 5.4 AU).
In the course of numerous studies, about 500 photographs of the comet's head and tail were obtained, about 100 spectrograms. A large number of determinations of the comet's position were also carried out, refining its orbit, which was of great importance in planning a program of research using spacecraft in anticipation of the next appearance in 1986. Based on studies of the outlines of the comet's head with the help of long-focus astrographs , SV Orlov constructed a theory of the formation of a cometary head.
Spectral analysis of the comet's tail showed that it contains the poisonous gas cyanogen and carbon monoxide . Since the Earth was supposed to pass through the tail of a comet on May 18, this discovery provoked predictions of the end of the world, panic and a rush of demand for quack "anti-comet pills" and "anti-comet umbrellas". In fact, as many astronomers were quick to point out, including Camille Flammarion , the comet's tail is so thin that it cannot have any negative effects on Earth's atmosphere .On May 18 and in the following days, various observations and studies of the atmosphere were organized, but no effects that could be associated with the action of cometary matter were found.
The famous American writer Mark Twain wrote in his autobiography in 1909: “I was born in 1835 with Halley's comet. She will appear again next year and I think we will disappear together. If I don't disappear with Halley's comet, it will be the greatest disappointment of my life. God probably decided: here are two bizarre inexplicable phenomena, they arose together, let them disappear together. " And so it happened: he was born on November 30, 1835, two weeks after the comet passed perihelion, and died on April 21, 1910, the day after the next perihelion.
Studies in 1986
The comet's appearance in 1986 was one of the least spectacular in history. In February 1986, during the passage of perihelion, the Earth and Halley's comet were on opposite sides of the Sun (on February 4, the comet was in upper conjunction with the Sun, and only 5 days later, on February 9, it passed perihelion ), which did not allow observing the comet during the period brightest when the size of its tail was at its maximum. In addition, due to the increased light pollution due to urbanization since the last time, the majority of the population could not observe the comet at all.In addition, when the comet was relatively bright in March and until the end of April, it was far in the Southern Hemisphere (passed through the constellations of the Southern Crown , Altar , Nagonnik , Wolf , Centauri ) and in the temperate latitudes of the Northern Hemisphere, the Earth was almost invisible, in the USSR it was then only visible in the southern regions, low above the horizon. Halley's comet approximation was first recorded by astronomers Jewitt and Danielson October 16, 1982 using the 5.1-m telescope of the Hale Palomar Observatory with CCD .The first person to visually observe the comet during its 1986 return was amateur astronomer Stephen James O'Meara, who on January 24, 1985, from the top of Mauna Kea, was able to detect the guest who had at that time magnitude 19.6. Stephen Edberg (works as coordinator of amateur astronomers observing at the Jet Propulsion Laboratory NASA's ) and Charles Morris first able to see Halley's comet with the naked eye. From 1984 to 1987, two comet observation programs were carried out: the Soviet SoproG and the international program The International Halley Watch (IHW).
The level of development of astronautics by this time provided scientists with the opportunity to explore the comet in close proximity, for which several spacecraft were launched . After the end of the Venus exploration program , the Soviet interplanetary stations "Vega-1" and "Vega-2" flew past the comet (the name of the spacecraft stands for "Venus-Halley" and indicates the route of the apparatus and the purpose of its study). "Vega-1" began transmitting images of Halley's comet on March 4, 1986 from a distance of 14 million km, for the first time in history... Vega-1 flew past the comet on March 6 at a distance of 8879 km. During the flight, the spacecraft was strongly affected by cometary particles at a collision speed of , as a result of which the power of the solar panels dropped by 45%, but the apparatus remained operational. Vega-2 flew past the comet at a distance of 8045 km on March 9. In total, both spacecraft transmitted more than 1,500 images to Earth, including about 70 images of the core. The images were used to determine the size of the core (8 × 8 × 16 km), the period (53 hours), the direction and approximate orientation of the axis of rotation, reflectivity (4%), characteristics of dust emissions, and the presence of ring craters was established.Measurement data from two Soviet stations were used in accordance with the joint research program to correct the orbit of the space probe of the European Space Agency " Giotto ", Which was able to fly even closer on March 14, to a distance of 605 km ( unfortunately, earlier, at a distance of about 1200 km, due to a collision with a fragment of a comet, the Giotto television camera went out of order, and the device lost control). A certain contribution to the study of Halley's comet was also made by two Japanese vehicles: " Suisei " (the original name was "Planet-A"; flyover on March 8, 150 thousand km) and " Sakigake " (March 10, 7 million km, was used to guide the previous apparatus).The five spacecraft that explored the comet have received the unofficial name " Halley's Armada ". The orbits of all these vehicles, in contrast to the orbit of Halley's comet, practically lay in the plane of the ecliptic ... Therefore, for their unlimited approach to the comet, it was necessary to fulfill two conditions: in space, the spacecraft should be close to one of the points of intersection of the comet's trajectory with the ecliptic plane - the descending or ascending node of its orbit, and the time of approach of the spacecraft to the node should be close to the time of passage through him comets ...The descending node was chosen, through which the comet passed after the passage of perihelion, on March 10, around this date, and all five vehicles approached the comet.
On the basis of data collected by the greatest while orbiting ultraviolet telescope " Astron " ( USSR ) under the supervision of Halley's comet in December 1985, a group of Soviet scientists developed a model of the cometary coma . The comet was observed from space and using the machine's " International Cometary Explorer " (originally called "International Sun researcher and Earth 3"), which was derived from the Lagrange point L1 on a heliocentric orbit for a meeting with the comet 21P / Giacobini - Zinner and Halley's comet.
Research on Comet Halley was included in the program of two missions of the space shuttle " Challenger " ( STS-51L and STS 61-E [planned for March 1986]), however, the "Challenger" disaster during the launch of the first mission on January 28, 1986 led to the death of the spacecraft and seven astronauts. Space platform for the study of comets " ASTRO-1 ", which was supposed to start the second mission, due to the suspension after the crash of the American manned spaceflight program, was launched into orbit only in December 1990, the mission of " Colombia " the STS-35 .
After 1986
February 12, 1991 at a distance of 14.4 a. That is, from the Sun, Halley's comet suddenly had an ejection of matter that lasted for several months and released a dust cloud about 300,000 km across. Halley's Comet last occurred 6-8 March 2003 three telescopes complex " Very Large Telescope " European Southern Observatory's (ESO's) , located on the mountain Cerro Paranal ( Chile ), when its magnitude is 28.2 and it has passed already 4/5 distances to the farthest point of its orbit ...These telescopes observed the comet at a record distance for comets (28.06 AU or 4200 million km) and magnitude, in order to work out methods for finding very faint trans-Neptunian objects . Now astronomers can observe a comet anywhere in its orbit. As of October 3, 2014, Halley's comet was in the constellation Hydra at a distance of almost 34 AU. That is, from the Sun , it is beyond the orbit of Neptune and beyond the position of Pluto at that time. The comet will reach aphelion in December 2023 , after which it will begin to approach the Sun again.
The next passage of Halley's comet through perihelion is expected on July 28, 2061, when its location will be more convenient for observation than during the passage in 1985-1986, since it will be on the same side of the Sun as the Earth at perihelion ... Its apparent magnitude is expected to be −0.3, up from +2.1 in 1986. On September 9, 2060, Halley's comet will pass at a distance of 0.98 AU . e. from Jupiter, and then on August 20, 2061, will approach a distance of 0.0543 AU. e. (8.1 million km) to Venus. Then Halley's comet will move away from the Sun and return again in 2134: it will pass through perihelion on March 27, and on May 7 it will pass at a distance of 0.09 AU. e. (13.6 million km) from the Earth.Its apparent magnitude at the time of this appearance will be about −2.0.
In art
Valery Leontyev's repertoire includes the song "Halley's Comet" (music by Raymond Pauls , lyrics by Nikolai Zinoviev , 1985).
The song with the same name is performed by the group Rondo .
In 1910 the "Zonofon" Society Orchestra performed the waltz of the same name.
Composer Andrei Rodionov created his own version of the song.
In 1910, Konstantin Balmont , Alexander Blok , Marina Tsvetaeva , Nikolai Gumilyov and other Russian poets widely used the image of Halley's comet in their poems.
The song of the American rock band Shinedown “ Second chanceThe lyrical hero mentions the vision of Halley's comet as the personification of the fact that the opportunity to make another choice in the foreseeable future may no longer be presented.
