Comet Heil-Bopp

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 .