C / 1975 V2 (Bradfield)

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C / 1975 V2 (Bradfield) [i]
Properties of the orbit ( animation )
Period:  December 22nd, 1975 ( JD 2,442,768.5)
Orbit type hyperbolic
Numerical eccentricity 1.000017
Perihelion 0.219 AU
Inclination of the orbit plane 70.6 °
Perihelion December 21, 1975
Orbital velocity in the perihelion 90.1 km / s
history
Explorer WA Bradfield
Date of discovery November 11, 1975
Older name 1975 XI, 1975p
Source: Unless otherwise stated, the data comes from JPL Small-Body Database Browser . Please also note the note on comet articles .

C / 1975 V2 (Bradfield) is a comet that could be seen with the naked eye around the turn of the year 1975/1976 .

Discovery and observation

The comet was in 1975 (local time) on the morning of 12 November from William A. Bradfield in Australia with a mm 150 - f / 5.5 - Refractor discovered. It was his fourth comet discovery, just eight months after his last. During this period he had searched for comets for a total of 106 hours. Bradfield estimated the comet's brightness to be about 10 mag. At first it could only be observed from the southern hemisphere .

By the end of November, when the comet reached its greatest southern declination , its brightness had increased to about 8 mag and by the first week of December to about 7 mag. Around the time it was passing the sun , the comet could not be observed for some time until it became visible to observers in the northern hemisphere towards the end of December . Observations of 3–4 mag with a tail less than 1 ° long have been reported .

After that, the brightness sank again quickly, by the end of January it had already fallen back to 10–11 mag. The last observation was on February 9, 1976.

Scientific evaluation

For this comet, after comet C / 1973 E1 (Kohoutek), the visibility of a counter-tail was calculated in advance for the second time , which should appear for a few weeks from the end of December. This was then also demonstrated photographically at the beginning of January 1976 , from which statements about the comet's dust production could be derived.

In a study from 1978 found Marsden , Sekanina and Everhart from 70 observations over a period of 74 days for the original web before passing through the inner solar system nor a hyperbolic shape, but the lay orbital eccentricity very close to 1, and an originally elliptical path was considered possible if non-gravitational influences had also been taken into account. A closed elliptical shape with an orbital period in the order of 23,500 years was determined for the future orbit of the comet .

Although some astronomers suspected an interstellar origin of this comet, Kresák came to the conclusion in his assessment in 1992 that a possible hyperbolic orbit shape for the comet Bradfield was based solely on the uncertainty of the orbit determination and that no interstellar origin could be assumed. This was confirmed in 2001 by an investigation by Królikowska.

In a more recent study in 2006, Królikowska determined new values ​​for the original orbit of the comet before the passage of the inner solar system and for its future orbit from 85 observation data over a period of 88 days, once only taking into account gravitational effects and once also taking into account non-gravitational effects. For the purely gravitational calculation, this study showed results that were similar to those of Marsden. When non-gravitational effects are taken into account, however, in contrast to Marsden's results, the original orbit of the comet was definitely closed elliptical.

Orbit

For the comet, a very precise hyperbolic orbit could be determined from 77 observation data over a period of 88 days , which is inclined by around 71 ° to the ecliptic . In the sun-next point on the path ( perihelion ), the comet has passed on 21 December 1975 he was with million 32.7 km distance from the Sun well within the orbit of the sun next planet Mercury . Already on November 30th it had approached Venus up to about 109.5 million km and on December 1st it had come close to Earth to about 1.06  AU / 158.3 million km. Only about three hours after its perihelion passage it reached the closest approach to Mercury with about 44.0 million km. On January 9, 1976, it came close to the earth again to about 1.07 AU / 160.6 million km.

The following statements are based on the non-gravitational orbital elements of Królikowska. Accordingly, the comet never moved on a hyperbolic orbit, but long before it approached the inner solar system in 1975 on an extremely elongated elliptical orbit with an orbital eccentricity of about 0.99992 and a semi-major axis of about 2800 AU. It thus had an orbital period on the order of 150,000 years. Due to the non-gravitational effects when passing close to the sun and due to the gravitational pull of the planets, especially during some relatively close passages of Saturn on December 31, 1973 in only about 2 ⅓ AU and on October 23, 1976 in about 7 ¼ AU , as well as on Jupiter on November 18, 1975 in about 5 AU and on February 24, 1977 in about 3 AU, the eccentricity was reduced to a value of about 0.99981 and the semi-major axis to about 1140 AU. The comet is likely to return to the inner solar system after about 38,000 years. However, these values ​​have a high level of uncertainty.

See also

Web links

Individual evidence

  1. ^ Astronomical Society of South Australia: Comets Discovered from South Australia. Accessed December 22, 2015 .
  2. ^ 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 ).
  3. ^ 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 ).
  4. ^ GW Kronk, M. Meyer: Cometography - A Catalog of Comets, Volume 5, 1960-1982. Cambridge University Press, Cambridge 2010, ISBN 978-0-521-87226-3 , pp. 489-492.
  5. ↑ Z. Sekanina, L. Pansecchi: The Anti-Tail of Comet Bradfield (1975p). In: Astrophysical Letters. Vol. 18, 1977, pp. 61-63 ( bibcode : 1977ApL .... 18 ... 61S ).
  6. ^ 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 ( bibcode : 1978AJ ..... 83 ... 64M ).
  7. ↑ Ľ. Kresák: Are there any comets coming from interstellar space? In: Astronomy and Astrophysics. Vol. 259, 1992, pp. 682-691 ( bibcode : 1992A & A ... 259..682K ).
  8. ↑ M. Królikowska: A study of the original orbits of “hyperbolic” comets. In: Astronomy and Astrophysics. Vol. 376, 2001, pp. 316-324 doi: 10.1051 / 0004-6361: 20010945 ( PDF; 173 kB ).
  9. ↑ a b M. Królikowska: The Oort spike modification due to non-gravitational effects. Submitted for publication in: Astronomy and Astrophysics. 2006, pp. 64-71 ( arxiv : astro-ph / 0609441 ).
  10. ↑ NASA JPL Small-Body Database Browser: C / 1975 V2 (Bradfield). Retrieved December 16, 2015 .
  11. ↑ A. Vitagliano: SOLEX 11.0. Archived from the original on September 18, 2015 ; accessed on May 2, 2014 .