C / 1975 V1 (West)

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C / 1975 V1 (West) [i]
Comet West on March 9, 1976
Comet West on March 9, 1976
Properties of the orbit ( animation )
Period:  March 3rd, 1976 ( JD 2,442,840.5)
Orbit type long-period
Numerical eccentricity 0.999971
Perihelion 0.197 AU
Aphelion 13560 AE
Major semi-axis 6780 AE
Sidereal period ~ 560,000 a
Inclination of the orbit plane 43.1 °
Perihelion February 25, 1976
Orbital velocity in the perihelion 95.0 km / s
history
Explorer Richard M. West
Date of discovery September 24, 1975
Older name 1976 VI, 1975n
Source: Unless otherwise stated, the data comes from JPL Small-Body Database Browser . Please also note the note on comet articles .

C / 1975 V1 (West) was a comet that could be seen with the naked eye during the day in 1976 . Due to its extraordinary brightness, it is counted among the " Great Comets ". It was the brightest comet since the sun streak Ikeya-Seki of 1965 and it is considered the most spectacular comet of the 20th century .

Discovery and observation

The La Silla Observatory of the European Southern Observatory was involved in a mapping project for the southern sky in the 1970s . The photographic plates obtained were evaluated by other astronomers in Geneva . Here was Richard M. West , a comet track on a recording, by early as September 24 on November 5, 1975 Guido Pizarro had been taken. He also looked for the comet on other photo plates from the same region of the sky and found further traces of the comet on photos that had already been taken on August 10th and 13th. The brightness of the comet was still below 14 mag.

From the first position measurements, Brian Marsden calculated preliminary orbital elements that indicated a short perihelion distance and a favorable observation situation for observers in the northern hemisphere at dawn from March 1976. The calculations also predicted an interesting, if not extraordinary, brightness development.

The first visual observations through a telescope were made on November 25th in the Philippines by Leo Boethin , who had already discovered comet 85D / Boethin himself this year . At the beginning of December the comet came into the observation area for astronomers in the northern hemisphere for a short time, where it could also be observed by Tsutomu Seki , but it remained visible all the time in the evening sky in the southern hemisphere .

By the beginning of January 1976 the brightness had increased to 8 mag and on January 14th an indistinct tail could be observed for the first time . Towards the end of January it became more difficult to observe the comet, which was now about 6 mag bright, as it was approaching the sun and could only be observed at dusk. It was now 2 may brighter than the prognoses had predicted, but few, if at all, expected it to develop into a large comet. Around the middle of February the brightness increased rapidly and by February 20 it reached 1 mag, the tail was 1 ° long, only two days later -1 mag was reported.

On February 25, the comet could be seen for the first time through telescopes in the daytime sky next to the sun . Shortly before sunset, a sighting with the naked eye was also possible. The brightness was estimated to be -2 to -3 mag. After the comet passed the Sun on February 26, it became visible at dawn. In the following days he was still observed in the daytime sky. The sudden increase in brightness was partly due to a favorable constellation, which resulted in forward scattering of the sunlight on the cometary dust, but this effect was also likely intensified by an unusually strong release of dust from the comet's core .

Comet West in March 1976

In early March, the comet appeared deep at dawn with a brightness of about -1 mag and a tail at least 2 ° long. After its closest approach to Earth on March 4th, its grandeur grew to full size. The tail quickly developed to a length of 30 to 40 ° on March 7th with significant thickening (striae). In addition to the dust tail, a 10 ° long plasma tail could be seen, as well as a wide fan that extended to the side of the main tail.

When the comet moved away from the sun and earth, its brightness and tail length soon decreased again. By mid-March the brightness had dropped to 3 mag and the dust tail was so faded that the plasma tail stood out more clearly. The comet could be followed with the naked eye until the first half of April, as it rose higher and higher in the morning sky. At the end of May a 1 ° long tail could still be seen in the powerful binoculars and at the end of June the brightness had dropped to 7.5 mag. The last visual observation was made on August 25 at a brightness of 11 mag. The last photographic observation was on September 25th.

The comet reached a magnitude of –1 mag on March 1, 1976 . The maximum brightness was reached with –2 mag.

Decay of the comet

At the beginning of March 1976 it could be determined for the first time that the comet's nucleus took on an elongated shape. On March 5, a clear split into two parts was found. A week later, two more fragments were observed.

Previously, fragmentation into so many fragments was only observed in the Great September Comet C / 1882 R1 and in 16P / Brooks 2 in 1889. The first of the two previously passed very close to the sun and the second very close to Jupiter . Neither was the case with Comet West. It was probably a massive burst of brightness that caused it to break. Something similar was observed in 1995 in 73P / Schwassmann-Wachmann 3 .

The fragments were given the designations A (the "main comet") to D. Of these, C was the smallest, which quickly faded. It was last seen on March 27th and likely completely dissolved after that. The other fragments remained detectable until the last photograph of the comet on September 25th. Shortly before, their brightness was around 20 mag.

Komet West photographed in the morning hours of March 3, 1976 at the vhs observatory in Neumünster

The process of fragmentation was theoretically investigated by Zdenek Sekanina and Ľubor Kresák . Then part D split off from the main body on February 19th, followed by B on February 27th and finally C on March 6th. These dates fit well with the first observed increase in brightness of the comet and the decay is the main cause of its enormous dust release and observed brightness.

Scientific evaluation

Comet West was the first comet on which extensive spectroscopic studies in the ultraviolet were made. The measuring devices for recording the ultraviolet spectrum of the comet in the wavelength range 120-320 nm were carried into the ionosphere on March 5, 1976 by an Aerobee 200 rocket . Investigations into the polarization of cometary radiation have also been undertaken.

The comet's particularly pronounced dust tail was examined more closely with regard to its dynamics and morphology. For this purpose, estimates of the total mass of the comet lost during the perihelion passage and the production rate of dust were derived.

The comet received special attention when it was noticed that it was beginning to split. This process is still a little understood process, which had been observed visually several times since the middle of the 19th century , but only rarely photographically or photometrically . Such studies were carried out at the University of Lecce , among others .

Orbit

For fragment A of the comet, Brian Marsden could unfortunately only calculate relatively imprecise orbital elements from 218 observation data over a period of 13 ½ months . Track elements could also be determined for fragments B and D. The orbital elements calculated by Marsden for fragment A are given in the info box and the following information also relates to this. The comet moves in an extremely elongated elliptical orbit , which is inclined by around 43 ° to the ecliptic . At the point of the orbit closest to the sun ( perihelion ), which the comet passed on February 25, 1976, it was located at a distance of 29.4 million km from the sun in the area within the orbit of Mercury . On February 29th it reached the closest approach to Earth with 0.79 AU / 118.8 million km and on March 9th it passed Venus at a distance of 111.5 million km .

The comet moved in a very elongated elliptical orbit before approaching the inner solar system . According to the orbital elements of fragment A, which are afflicted with a certain degree of uncertainty, its orbit previously had an eccentricity of around 0.99969 and a semi-major axis of around 637 AU, so that its orbital period was around 16,000 years. This value was also given by Marsden, Sekanina and E. Everhart, who calculated its original and future orbit. Due to the attraction of the planets, its orbital eccentricity was increased to a value very close to 1, so that its point furthest from the sun ( aphelion ) should now again be within the Oort cloud . Marsden, Sekanina and Everhart calculated an orbital period of 6.4 million years for this. When it returns to the inner solar system afterwards, it will falsely appear as if it were a "dynamic new" comet, although due to its tendency to decay it may already be its last visit to the sun. For fragments B and D there will possibly not be a return to the inner solar system, since Syuichi Nakano derived orbital elements with eccentricities> 1 for both, and which therefore now probably leave the solar system on hyperbolic orbits.

Reception in the media

This comet received little attention in the media after the exaggerated expectations that had been fueled in advance of comet C / 1973 E1 (Kohoutek) were disappointed by its "fiasco" the following year. As a result, many who were not astronomers were not informed of the comet's beauty until it was too late. And even for astronomers, the extraordinary development of Comet West was as surprising as it was for most others.

In the Republic of Congo was one on 17 February 1986 Airmail - special stamp to 150 CFA francs with a picture of the comet West occasion of the publication of Halley's Comet edited.

See also

Web links

Individual evidence

  1. ^ BG Marsden, E. Roemer: Comets in 1975. In: Quarterly Journal of the Royal Astronomical Society. Vol. 19, 1978, pp. 59-89 ( bibcode : 1978QJRAS..19 ... 59M ).
  2. ^ BG Marsden, DWE Green, E. Roemer: Comets in 1976. In: Quarterly Journal of the Royal Astronomical Society. Vol. 26, 1985, pp. 68-80 ( bibcode : 1985QJRAS..26 ... 68M ).
  3. ^ A b G. W. Kronk, M. Meyer: Cometography - A Catalog of Comets. Volume 5: 1960-1982 . Cambridge University Press, Cambridge 2010, ISBN 978-0-521-87226-3 , pp. 477-489.
  4. ↑ a b c D. AJ Seargent: The Greatest Comets in History: Broom Stars and Celestial Scimitars . Springer, New York 2009, ISBN 978-0-387-09512-7 , pp. 152-157.
  5. ^ Peter Grego: Blazing a Ghostly Trail: ISON and Great Comets of the Past and Future . Springer, Cham 2013, ISBN 978-3-319-01774-7 , pp. 136-137.
  6. ^ Donald K. Yeomans: NASA JPL Solar System Dynamics: Great Comets in History. Retrieved June 17, 2014 .
  7. ^ P. Moore, R. Rees: Patrick Moore's Data Book of Astronomy . Cambridge University Press, Cambridge 2011, ISBN 978-0-521-89935-2 , p. 271.
  8. ^ PD Feldman, WH Brune: Carbon production in comet West 1975n. In: Astrophysical Journal. Vol. 209, 1976, pp. L45-L48 ( bibcode : 1976ApJ ... 209L..45F ).
  9. ^ PD Feldman: Ultraviolet Albedo of Comet West (1976 VI). In: Solid particles in the solar system; Proceedings of the Symposium, Ottawa, Canada, August 27-30, 1979. D. Reidel Publishing Co., Dordrecht 1980, pp. 263-266 ( bibcode : 1980IAUS ... 90..263F ).
  10. ^ S. Isobe, K. Saito, K. Tomita, H. Maehara: Polarization of the Head of Comet 1976 VI West. In: Publications of the Astronomical Society of Japan. Vol. 30, 1978, pp. 687-690 ( bibcode : 1978PASJ ... 30..687I ).
  11. ^ NN Kiselev, GP Chernova: Polarization of the radiation of comet West, 1975n. In: Soviet Astronomy. Vol. 22, 1978, pp. 607-611 ( bibcode : 1978SvA .... 22..607K ).
  12. ^ T. Akabane: The Secondary Tail of Comet 1976 VI West. In: Publications of the Astronomical Society of Japan. Vol. 35, 1983, pp. 565-578 ( bibcode : 1983PASJ ... 35..565A ).
  13. ↑ CB Cosmovici, F. Strafella, L. Dimagli, A. D'Innocenzo, G. Leggieri, C. Nesta, A. Perrone: Splitting of Comet West 1975n: Photography and Narrow-band Photometry. In: Astronomy and Astrophysics. Vol. 63, 1978, pp. 83-86 ( bibcode : 1978A & A .... 63 ... 83C ).
  14. ↑ NASA JPL Small-Body Database Browser: C / 1975 V1-A. Retrieved October 16, 2014 .
  15. ↑ SOLEX 11.0 A. Vitagliano. Archived from the original on September 18, 2015 ; accessed on May 2, 2014 .
  16. ^ BG Marsden, Z. Sekanina, E. Everhart: New Osculating Orbits for 110 Comets and Analysis of Original Orbits for 200 Comets. In: The Astronomical Journal. Vol. 83, no. 1, 1978, pp. 64-71 doi: 10.1086 / 112177 .
  17. ^ Colnect. Retrieved October 16, 2014 .