C / 1997 O1 (Tilbrook)

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C / 1997 O1 (Tilbrook) [i]
Properties of the orbit ( animation )
Epoch:  September 24, 1997 ( JD 2,450,715.5)
Orbit type long-period
Numerical eccentricity 0.984
Perihelion 1.37 AU
Aphelion 172.7 AU
Major semi-axis 87.0 AU
Sidereal period ~ 812 a
Inclination of the orbit plane 115.8 °
Perihelion July 13, 1997
Orbital velocity in the perihelion 35.8 km / s
history
Explorer J. Tilbrook
Date of discovery July 22, 1997
Source: Unless otherwise stated, the data comes from JPL Small-Body Database Browser . Please also note the note on comet articles .

C / 1997 O1 (Tilbrook) is a comet that was observed in 1997.

discovery

The comet was on the evening of July 22 1997 (local time) by amateur astronomers Justin Tilbrook in Clare north of Adelaide in South Australia with a mm 200 - f / 6 - Reflector discovered. It was his first and accidental discovery of a comet. Tilbrook, a seasoned variable star observer , wasn't actually looking for comets. When he wanted to watch the dwarf nova TV Corvi on the evening of July 22nd , he noticed a washed-out spot nearby. Because he was familiar with the star field, he knew he hadn't seen anything there before. He noted the position and was able to determine after 1 ½ hours that the spot had moved. Tilbrook described the comet as diffuse and estimated its brightness to be around 10 mag. The discovery of the new comet was officially confirmed by the IAU the very next day .

Had the comet been discovered three months earlier, it would have been seen with binoculars . But although since March it has always had an elongation from the sun greater than 60 ° , at that time it was moving through areas of the southern sky that are very rich in stars, star clusters and nebulae . In addition, its discovery was made more difficult by the fact that bad weather prevailed for a long time in the southern hemisphere during winter .

Initially, the comet could only be observed from the southern hemisphere and southern areas of the northern hemisphere . At the end of July its brightness reached between 10 and 11 mag, by the end of August it had fallen to 12 mag. The comet could not be observed from northern latitudes until September. The last position was determined on March 23, 1998 at a brightness of only about 18 mag at the Astronomical and Geophysical Observatory in Modra , Slovakia .

Scientific evaluation

With the Solar Wind Anisotropies (SWAN) instrument on board the SOHO space probe , the entire sky was mapped in the ultraviolet light of the Lyman α line of hydrogen at 121.5 nm from the end of 1996 to mid-1998 . Several comets could be identified through their very extensive hydrogen envelopes. In this way, the comet Tilbrook could be subsequently detected in 41 images between May 20 and August 26, 1997, two months before its actual discovery. Since the comet's hydrogen shell is essentially formed by the photodissociation of water , the production rate of water for the comet could also be determined.

Orbit

A relatively precise elliptical orbit could be determined for the comet from 115 observation data over a period of 243 days , which is inclined by around 116 ° to the ecliptic . It thus runs in the opposite direction (retrograde) like the planets through its orbit. At the point of the orbit closest to the sun ( perihelion ), which the comet last traversed on July 13, 1997, it was located at a distance of 205.2 million km from the sun in the area between the orbits of Earth and Mars . On June 24th it had already come close to the earth to 0.91  AU / 136.7 million km. On July 31st, it approached Mars up to about 41.3 million km and on August 12th, Venus up to about 107.9 million km.

The comet moves in an extremely elongated elliptical orbit around the sun. According to the orbital elements , which are afflicted with a certain uncertainty, its orbit had an eccentricity of about 0.9843 and a semi-major axis of about 87.5 AU some time before the passage through the inner solar system in 1997 , so that its orbit period was about 819 years. The comet could therefore have last appeared in the year 1178 or 1179 ( uncertainty ± 11 months), although it apparently remained undetected due to its low brightness. Due to the gravitational pull of the planets, in particular by passing close by Saturn on April 23, 1996 in 6 ¾ AU and on Jupiter on May 9, 1997 in 4 ½ AU, the orbital eccentricity was reduced to about 0.9833 and the major axis to about 82 .1 AU, so that its orbital period was shortened to about 744 years. When it reaches the point of its orbit furthest from the sun ( aphelion ) in 2369 (uncertainty ± 4 months) , it will be about 24.4 billion km from the sun, over 160 times as far as the earth and almost 5½- times as far as Neptune . Its orbital speed in the aphelion is only about 0.30 km / s. The next perihelion of the comet is expected to take place around the year 2741 (uncertainty ± 9 months).

See also

Web links

Individual evidence

  1. ^ Comets Discovered from South Australia. Astronomical Society of South Australia, accessed June 2, 2016 .
  2. ^ A Tale of Discovery. Astronomical Society of South Australia, accessed June 2, 2016 (with photo of J. Tilbrook and the comet).
  3. ^ DWE Green: IAUC 6705: 1997 01; BL Lac. IAU Central Bureau for Astronomical Telegrams, accessed June 2, 2016 .
  4. ^ J. Shanklin: The comets of 1997. In: Journal of the British Astronomical Association. Vol. 112, 2002, pp. 130-150 ( bibcode : 2002JBAA..112..130S ).
  5. ^ C / 1997 O1 (Tilbrook). IAU Minor Planet Center, accessed June 3, 2016 .
  6. ↑ JTT Mäkinen, J.-L. Bertaux, TI Pulkkinen, W. Schmidt, E. Kyrölä, T. Summanen, E. Quémerais, R. Lallement: Comets in full sky L α maps of the SWAN instrument. I. Survey from 1996 to 1998. In: Astronomy & Astrophysics. Vol. 368, 2001, pp. 292-297 doi: 10.1051 / 0004-6361: 20000545 ( PDF; 250 kB ).
  7. ↑ NASA JPL Small-Body Database Browser: C / 1997 O1 (Tilbrook). Retrieved June 1, 2016 .
  8. ↑ A. Vitagliano: SOLEX 11.0. Archived from the original on September 18, 2015 ; accessed on May 2, 2014 .