C / 1987 P1 (Bradfield)

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C / 1987 P1 (Bradfield) [i]
Properties of the orbit ( animation )
Epoch:  November 29, 1987 ( JD 2,447,128.5)
Orbit type long-period
Numerical eccentricity 0.9947
Perihelion 0.869 AU
Aphelion 329 AU
Major semi-axis 165 AU
Sidereal period ~ 2120 a
Inclination of the orbit plane 34.1 °
Perihelion November 7, 1987
Orbital velocity in the perihelion 45.1 km / s
history
Explorer WA Bradfield
Date of discovery August 11, 1987
Older name 1987 XXIX, 1987s
Source: Unless otherwise stated, the data comes from JPL Small-Body Database Browser . Please also note the note on comet articles .

C / 1987 P1 (Bradfield) is a comet that could be seen with the naked eye in 1987 .

Discovery and observation

The comet was on the evening of August 11, 1987 by William A. Bradfield in Australia with a mm 150 - f / 5.5 - Refractor discovered. It was his 13th comet discovery, around 3½ years after his last. During this period he searched for comets for a total of 307 hours. He was the first person in the 20th century to discover more than a dozen comets, all of them as sole discoverers.

At the time of its discovery, the comet was moving in the constellation Water Snake when it was 1.57 AU from Earth and 1.72 AU from the Sun. Despite its already relatively high brightness of 10 mag, it was apparently not discovered earlier because, at the time of his opposition in mid-May of the year, at a brightness of 12 mag, it was in the starry regions of the southern Milky Way . From October the comet was also visible in the northern hemisphere . Its brightness increased rapidly, on October 10th it was still around 7 mag, by the end of the month the comet was also visible to the naked eye and reached around 5 mag in November 1987. It was the brightest comet since the return of the Halley's Comet in 1986. After that, it became weaker again and could no longer be seen with the naked eye from mid-December. At the turn of the year it had reached its greatest elongation from the sun at almost 90 ° . His last observation was on April 13, 1988.

In addition to a nearly 2 ° long plasma tail, the comet also showed a clear counter- tail for a short time .

Scientific evaluation

In addition to the comet-typical emission lines of CN, C 2 and C 3 , those of silicates ( olivine ) could also be determined to a high degree in the comet's spectrum . An estimate of the mass loss of the comet resulted in a value of over 10 6  g / s at a distance of 1.45 AU from the sun. Assuming that the entire sun-lit hemisphere of the comet's nucleus secretes material, this gives a lower limit for the radius of the nucleus of 1.3 km.

The light emanating from the cometary coma was examined with regard to its polarization , and conclusions could be drawn from the measurement results about the size and material of the dust particles. There were also indications of silicates.

In October and November 1987, observations of the 18 cm OH emission line at Comet Bradfield were made with the Nançay radio telescope . A clear signal was found, from which the production rate of the OH radical could be derived.

Photographs of the comet's plasma tail were used to determine the physical conditions of the comet's atmosphere and the surrounding interplanetary space and to develop mathematical models for the observed effects. The speed of the solar wind in the vicinity of the comet was derived from recordings of the plasma tail and compared with satellite measurements in the vicinity of the earth.

A variability with a period of 6 days could be demonstrated in the brightness curve of the comet. This may indicate a rotation of the comet's nucleus with the same period.

Orbit

For the comet, a very precise elliptical orbit could be determined from 574 observation data over a period of 245 days , which is inclined by around 34 ° to the ecliptic . At the point of the orbit closest to the sun ( perihelion ), which the comet last traversed on November 7, 1987, it was about 130.0 million km from the sun, between the orbits of Venus and Earth . On December 12th it approached the earth within 0.83  AU / 124.7 million km.

The comet moves in an extremely elongated elliptical orbit around the sun. Based on the currently known, very precise orbital elements , its orbit had an eccentricity of about 0.9945 and a semi-major axis of about 157 AU some time before its passage through the inner solar system in 1987 , so that its orbit was around 1960 years. The comet could have appeared in ancient times around the year 27 ( uncertainty ± 1.7 years). Due to the gravitational pull of the planets, especially due to the relatively close passages of Saturn on September 1, 1986 in about 7 ⅓ AU and on Jupiter on February 23, 1988 in about 3 ¾ AU, its orbital eccentricity was reduced to about 0.9936 and its size Semi-axis reduced to about 135 AU, so that its orbital period was shortened to about 1565 years. When it reaches the point of its orbit furthest from the sun ( aphelion ) around the year 2773 , it will be 40.2 billion km from the sun, almost 270 times as far as the earth and 9 times as far as Neptune . Its orbit speed in the aphelion is only 0.16 km / s. The next perihelion of the comet is expected to take place around the year 3552 (uncertainty ± 1.2 years).

See also

Web links

Individual evidence

  1. ^ Astronomical Society of South Australia: Comets Discovered from South Australia. Retrieved January 14, 2016 .
  2. ↑ a b R. Luthardt (ed.): Ahnert's calendar for Sternfreunde 1990: Kleines astronomisches Jahrbuch . JA Barth Verlag, Leipzig 1989, ISBN 3-335-001974 , p. 165.
  3. ^ Peter Grego: Blazing a Ghostly Trail: ISON and Great Comets of the Past and Future . Springer, Cham 2013, ISBN 978-3-319-01774-7 , p. 266.
  4. ^ SJ Edberg: Observing Comets, Asteroids, Meteors, and the Zodiacal Light . Cambridge University Press, Cambridge 1994, ISBN 978-0521420037 , p. 16.
  5. ↑ BS Rautela, BB Sanwal: Spectrophotometric Study of Comet Bradfield (1987s). In: Earth, Moon, and Planets. Vol. 43, No. 3, 1988, pp. 221-225 doi: 10.1007 / BF00117094 .
  6. ↑ MS Hanner, RL Newburn, RD Gehrez, T. Harrison, EP Ney, TL Hayward: The infrared spectrum of Comet Bradfield (1987s) and the silicate emission feature. In: The Astrophysical Journal. Vol. 348, 1990, pp. 312-321, doi: 10.1086 / 168237 , bibcode : 1990ApJ ... 348..312H .
  7. ↑ S. Kikuchi, Y. Mikami, T. Mukai, S. Mukai: Polarimetry of comet Bradfield (1987s). In: Astronomy and Astrophysics. Vol. 214, 1989, pp. 386-388, bibcode : 1989A & A ... 214..386K .
  8. ↑ D. Paul, A. Suklabaidya, HS Das, AK Sen: Study of polarization properties of comet Bradfield 1987 P1 using aggregate dust model and its comparison with comet NEAT C / 2001 Q4. In: Assam University Journal of Science & Technology: Physical Sciences and Technology. Vol. 6, No. II, 2010, pp. 30–33 ( PDF; 74 kB ( Memento of the original dated December 11, 2015 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and Archive link according to instructions and then remove this note. ). @1@ 2Template: Webachiv / IABot / www.inflibnet.ac.in
  9. ↑ J. Crovisier, P. Colom, E. Gérard, D. Bockelée-Morvan, G. Bourgois: Observations at Nançay of the OH 18-cm lines in comets - The data base. Observations made from 1982 to 1999. In: Astronomy & Astrophysics. Vol. 393, 2002, pp. 1053-1064 doi: 10.1051 / 0004-6361: 20020673 ( PDF; 391 kB ).
  10. ↑ SA Borysenko, Yu. V. Sizonenko, IV Luk'yanyk, AV Ivanova, AD Voitsekhovskaya, TP Sergeeva, AV Golovin: Physical Conditions in the Plasma Tail of Comet C / 1987 P1 Bradfield. In: Kinematics and Physics of Celestial Bodies. Vol. 27, No. 2, 2011, pp. 92-97 doi: 10.3103 / S0884591311020024 .
  11. ↑ D. Kubáček, EM Pittich, J. Zvolankova, J. Tichá, M. Tichý: aberration angles of comet Bradfield 1987 XXIX plasma tail. In: Contributions of the Astronomical Observatory Skalnaté Pleso. Vol. 25, 1995, pp. 83-89, bibcode : 1995CoSka..25 ... 83K .
  12. ↑ J.-I. Watanabe, T. Abe: Periodic Activity of Comet Bradfield 1987s. In: Earth, Moon, and Planets. Vol. 44, No. 2, 1989, pp. 141-147 doi: 10.1007 / BF00056313 .
  13. ↑ NASA JPL Small-Body Database Browser: C / 1987 P1 (Bradfield). Retrieved December 8, 2015 .
  14. ↑ SOLEX 11.0 A. Vitagliano. Archived from the original on September 18, 2015 ; accessed on May 2, 2014 .