C / 1995 O1 (Hale-Bopp)
| C / 1995 O1 (Hale-Bopp) [i] | |
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| Comet C / 1995 O1 Hale-Bopp | |
| Properties of the orbit ( animation ) | |
| Orbit type | long-period |
| Numerical eccentricity | 0.995 |
| Perihelion | 0.914 AU |
| Aphelion | 371.5 AU |
| Major semi-axis | 186.2 AU |
| Sidereal period | ~ 2540 a |
| Inclination of the orbit plane | 89.430 ° |
| Perihelion | April 1, 1997 |
| Orbital velocity in the perihelion | 44.005 km / s |
| Physical properties of the core | |
| Medium diameter | ~ 60 km |
| history | |
| Explorer | A. Hale , T. Bopp |
| Date of discovery | July 23, 1995 |
| Source: Unless otherwise stated, the data comes from JPL Small-Body Database Browser . Please also note the note on comet articles . | |
The comet Hale-Bopp (C / 1995 O1) was discovered independently on July 23, 1995 by Alan Hale in New Mexico and Thomas Bopp in Arizona when they observed the globular cluster M 70 in the constellation Sagittarius. The first unconscious imaging of the comet was taken in 1993 from the Siding Spring Observatory (Australia) and was discovered when archive material was viewed again. It was suspected early on that it would get very bright near the sun. The prediction was confirmed when he went through perihelion on April 1, 1997. Hale-Bopp was therefore also referred to as The Great Comet of 1997 . It was probably the most watched comet of the 20th century and one of the brightest for several decades. The comet could be seen freely over a period of 18 months - twice as long as the previous record holder Flaugergues (The Great Comet of 1811) .
Orbit
The comet runs on an extremely elongated orbit with a numerical eccentricity of 0.995 around the sun, its orbital plane is almost exactly perpendicular to the ecliptic with an inclination of 89.4 ° . The perihelion , the point of its orbit closest to the sun, is 0.914 AU just inside the earth's orbit , its point furthest from the sun, the aphelion , is 371.5 AU.
Since its orbit is almost perpendicular to the ecliptic, it is generally very unlikely to get close to the planets. However, in March 1996 it passed Jupiter at a distance of 0.77 AU, which was close enough to significantly change the comet's orbit due to Jupiter's gravitational influence. This shortened the comet's orbital period from around 4200 years to 2380 years, so that it will return to the inner solar system around the year 4419 . Before the encounter with Jupiter, his aphelion with 525 AU was accordingly further out.
Evolution of the cometary event
discovery
Before he discovered the comet, Alan Hale had already spent several hundred hours of observation on a systematic search for comets, but without having discovered a new comet. In New Mexico , while observing well-known comets near the globular cluster M 70 in the constellation Sagittarius , he finally noticed the comet later known as Hale-Bopp, which at the time had an apparent magnitude of eleven magnitudes . First, Hale convinced himself that he was not observing any other deep-sky object in the vicinity of M 70 and did not find anything in the catalogs of well-known comets. When he finally noticed that the object was moving relative to the background stars, he sent an email to the IAU's Central Bureau of Astronomical Telegrams at the Harvard-Smithsonian Center for Astrophysics to report his possible discovery of a new comet .
Thomas Bopp, on the other hand, discovered the comet rather accidentally with a friend's telescope while he was out with friends near Stanfield , Arizona , to observe star clusters and galaxies . After discovering the faint object, he used his star atlases and, like Alan Hale, determined that there is no deep sky object near M70. He then contacted the Central Bureau of Astronomical Telegrams by telegram .
The next morning it was confirmed that it was a new comet. The discovery was announced in Circular 6187 of the International Astronomical Union . The comet was named after its discoverer Hale-Bopp and was given the designation C / 1995 O1.
First investigations
It quickly turned out that Hale-Bopp is no ordinary comet. When you calculated your orbit , you got a distance of 7.2 AU from the Sun at the time of discovery , i.e. between Jupiter and Saturn , which was by far the greatest distance at which a comet was discovered (2017 exceeded by C / 2017 K2 ). Most comets are extremely weak at this distance and show no noticeable activity, but Hale-Bopp was able to detect a coma at this distance . An image taken in 1993 by the Anglo-Australian Telescope shows the then undiscovered comet at a distance of 13 AU from the Sun, a distance at which most comets are unobservable ( Halley's Comet was only 1 / 50,000 the brightness at the same distance ). The size of the comet's nucleus is estimated at 50 km, making it three times the size of Halley's comet, and larger than any other known comet.
Since it was already so bright at a great distance, it was assumed early on that Comet Hale-Bopp would become very bright when it reached perihelion in 1997. However, many comets have violent bursts of brightness at a greater distance, only to lapse into a phase of calm again afterwards, which is why one was initially careful with a brightness prognosis, also in order not to arouse too high expectations. Comet Kohoutek was named “Comet of the Century” in advance in 1973, but in the end it was hardly impressive.
Perihelion of the comet
From the summer of 1996, Hale-Bopp could already be seen with the naked eye at a distance of 2 AU from the sun . Even though it didn't get brighter as quickly as it got closer to the sun, scientists were now cautiously optimistic that it would get very bright. In December 1996 it was in line of sight of the sun when viewed from Earth and therefore could not be observed; However, when it reappeared in January 1997, it could no longer be overlooked even in cities with their high levels of light pollution .
In addition, the widespread use of the Internet around 1996 contributed significantly to the unprecedented interest in Hale-Bopp. On numerous websites you could follow the flight of the comet with new pictures every day.
In February 1997 the comet reached an apparent magnitude of 2 m and showed two growing tails . The blue gas tail pointed directly away from the sun, while the yellow dust tail pointed towards its orbit. On March 9, a solar eclipse in Mongolia and Eastern Siberia allowed the comet to be seen during the day. On March 22, 1997, Hale-Bopp was closest to Earth at 1.315 AU. Most other comets would not be visible to the naked eye at this distance. When the comet passed its perihelion on April 1, 1997, it had developed into an impressive spectacle with an apparent brightness of about −1 m . It seemed brighter than any star except Sirius, and its two tails stretched across the sky over an angle of 30 to 40 degrees. It was visible before it got really dark and remained visible all night in the northern hemisphere .
Fading comet
After it had reached its perihelion, the comet moved behind the southern horizon and could no longer be observed from the northern hemisphere, so that there was no longer any interest in it. In the southern hemisphere it was much less impressive than in the northern hemisphere , but from there you could see how it gradually faded in the summer and fall of 1997. Hale-Bopp was visible to the naked eye for 569 days, from May 20, 1996 to December 9, 1997, about 18.5 months, more than twice as long as the previous record holder Comet Flaugergues (C / 1811 F1 ) - the Great Comet of 1811 - which was observed with the naked eye for 9 months. Hale-Bopp was also brighter than 0 m for eight weeks - longer than any other comet in the past thousand years. It caused a far greater stir than Halley's Comet in 1986. It can be assumed that no other comet has ever been seen by as many people as Hale-Bopp.
In February and March 2001, the comet was observed at a distance of 13 AU with the 2.2 m telescope at the La Silla Observatory . Despite its great distance from the Sun (beyond the orbit of the planet Saturn ), the comet still exhibited a coma with a diameter of 2 million kilometers.
The comet continued to decrease in brightness, but was still observed by astronomers. In January 2005 it was at a distance of 21 AU further from the Sun than Uranus , but could still be seen with large telescopes. Observations showed that at this point it still had a small tail.
Astronomers expect it to be observable by around 2020, when it will have an apparent magnitude of 30 m . After that it will be very difficult to distinguish it from the background galaxies, which have a similar brightness. Comet Hale-Bopp will return around the year 4419.
Scientific results
Hale-Bopp was closely watched by astronomers during its passage through the inner solar system , which led to some new knowledge about comets.
Sodium tail
One of the most notable discoveries was a third tail. In addition to the gas and dust tails already known from other comets, Hale-Bopp also had a thin sodium tail . But it was only visible with the help of large telescopes and special filters. Sodium has already been detected in tails of other comets, but not as a separate tail. Hale-Bopp's sodium tail was made up of neutral atoms and was 50 million kilometers long.
Although the sodium came from the internal coma, it does not necessarily have to come from the nucleus, as sodium can be excreted through a number of mechanisms. This includes, for example, the collision with dust grains that are located around the nucleus, in which ultraviolet light from the sun releases the sodium from these grains.
While the dust tail followed roughly the comet's orbit, and the gas tail pointed almost directly away from the sun, the sodium tail was between the two. This suggests that the sodium atoms were pushed away from the comet's core by the radiation pressure .
Deuterium occurrence
The proportion of deuterium (in heavy water ) at Hale-Bopp is twice as high as in the oceans of the earth. According to a popular theory of the origin of terrestrial water , comet impacts contributed most of the water on earth, but they cannot have been the only source. In addition to Hale-Bopp's deuterium content, the deuterium content was also determined by Churyumov-Gerasimenko and is also too high for terrestrial water.
Deuterium was also found in many other hydrogen compounds in the comet. Since the amount of deuterium varies from compound to compound, scientists conclude that the comet's ice formed in interstellar clouds rather than the protoplanetary disk . Theoretical models of ice in interstellar clouds show that Hale-Bopp was formed at an ambient temperature of around 24-25 Kelvin .
Organic ingredients
Spectroscopic observations by Hale-Bopp revealed the presence of several organic compounds ( HCOOH , HCOOCH 3 , HC 3 N , CH3CN ); many of them have never been seen in comets before. These complex molecules could already have existed in the comet or they could have been formed by chemical reactions in the coma.
rotation
The gas emitted by Hale-Bopp did not come out of its core evenly, but in the form of several large jets in different places. The observations of the jets made it possible to determine the period of rotation of the comet. It is 11 hours and 46 minutes. Since the period of rotation obtained in this way showed several periodic fluctuations, one suspects that the comet rotates around more than one axis .
Possible satellite
In a technical paper published in 1999 it was argued that assuming two cometary nuclei could fully explain the shape of Hale-Bopp's dust emissions. However, the assumption is based only on theoretical analyzes and no direct observation of a second core. According to these analyzes, the second core should have a diameter of around 30 km, while the main core has a diameter of around 70 km. Both cores are to rotate around their common axis every 3 days at a distance of around 180 km.
The publication has been discussed by many astronomers, but even with high resolution telescopes like the Hubble Space Telescope , no tail of a double nucleus could be seen. Although it is quite common for comets to break apart, a case has never been observed in which two nuclei orbit each other in a stable manner because they are easily disturbed by the gravitational influence of the sun or other planets.
Observations with adaptive optics in late 1997 / early 1998 showed two brightness peaks in the comet. However, there is still controversy as to whether all observations can be explained by just the presence of two nuclei.
Paranoia and superstition
In many cultures, comets were viewed as bad omen and followed with great suspicion. Even today, their appearance is regularly accompanied by paranoia and superstition. Perhaps because of its long increase in brightness and its unusual size, Hale-Bopp has been the subject of so many bizarre beliefs and theories.
In November 1996, the amateur astronomer Chuck Shramek of Houston , Texas, took a CCD image of the comet, near which a fuzzy, somewhat elongated object could be seen. When he could not identify the star with the help of his electronic star catalog, Shramek notified the radio station Art Bell that he had seen a Saturn-like object that was following Hale-Bopp. UFO fanatics like Courtney Brown quickly came to believe that an alien spaceship was following the comet. In reality it was the star SAO141894 with an apparent magnitude of 8.5 m . It did not appear in Shramek's computer program because his user settings were inaccurate. When confronted with this, Shramek did not admit the mistake.
Art Bell later claimed they had a picture taken by an anonymous astrophysicist confirming his discovery. However, astronomers Olivier Hainaut and David J. Tholen at the University of Hawaii showed that it was just an altered copy of one of their own images.
Two months later, in March 1997, 39 members of the Heaven's Gate sect committed mass suicide in the face of the comet that had appeared . Their motive was that they would leave their earth body and travel to the spaceship that accompanied the comet.
See also
- List of comets
- Hale Bopp , composition (1997)
- Hale-Bopp , single release by the Berlin reggae band Seeed (2020)
Individual evidence
- ↑ D. Yeomans (1997): Orbit and Ephemeris Information for Comet Hale-Bopp (1995 O1) , accessed January 3, 2016
- ^ DWE Green: IAU Circular 6187 , July 23, 1995
- ↑ G. Cremonese, H. Boehnhardt, J. Crovisier et al .: Neutral Sodium from Comet Hale-Bopp: A Third Type of Tail . In: The Astrophysical Journal Letters . tape 490 , no. 2 , 1997, p. L199 , doi : 10.1086 / 311040 , arxiv : astro-ph / 9710022 (English, iop.org [accessed on July 7, 2020]).
- ↑ SD Rodgers, SB Charnley (2001), Organic synthesis in the coma of Comet Hale-Bopp? , Monthly Notices of the Royal Astronomical Society, Vol. 320, pp. L61-L64. bibcode : 2001MNRAS.320L..61R
- ↑ J. Warell, C.-I. Lagerkvist, JSV Lagerros (1999): Dust continuum imaging of C / 1995 O1 (Hale-Bopp) :. Rotation period and dust outflow velocity , Astronomy and Astrophysics Supplement, Vol. 136, p. 245, bibcode : 1999A & AS..136..245W
- ↑ Z. Sekanina (1999), Detection of a Satellite Orbiting The Nucleus of Comet Hale-Bopp (C / 1995 O1) , Earth, Moon, and Planets, Vol. 77, p. 155, doi : 10.1023 / A: 1006230712665
- ↑ F. Marchis, H. Boehnhardt, OR Hainaut, D. Le Mignant (1999): Adaptive optics observations of the innermost coma of C / 1995 O1. Are there a "Hale" and a "Bopp" in comet Hale-Bopp? , Astronomy and Astrophysics, Vol. 349, p. 985, bibcode : 1999A & A ... 349..985M
- ^ Russell Sipe, The "Object" Near Comet Hale-Bopp , accessed November 28, 2006; no longer online, but The "Object" Near Comet Hale-Bopp ( Memento from June 27, 2007 in the Internet Archive ), accessed on Nov. 8, 2013
- ↑ Olivier R. Hainaut and Dr. David J. Tholen: Fraudulent use of a IfA / UH picture ( memento of March 10, 2009 in the Internet Archive ) , January 15, 1997
swell
- Newcott, William R. (Dec. 1997). The age of comets in National Geographic , p. 100.
- http://www.eso.org/public/news/eso9520/
