C / 1980 Y1 (Bradfield)

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C / 1980 Y1 (Bradfield) [i]
Properties of the orbit ( animation )
Epoch:  December 27, 1980 ( JD 2,444,600.5)
Orbit type long-period
Numerical eccentricity 0.99973
Perihelion 0.260 AU
Aphelion 1889 AE
Major semi-axis 945 AU
Sidereal period ~ 29,000 a
Inclination of the orbit plane 138.6 °
Perihelion December 29, 1980
Orbital velocity in the perihelion 82.6 km / s
history
Explorer WA Bradfield
Date of discovery 17th December 1980
Older name 1980 XV, 1980t
Source: Unless otherwise stated, the data comes from JPL Small-Body Database Browser . Please also note the note on comet articles .

C / 1980 Y1 (Bradfield) is a comet that could be seen with the naked eye in 1980 and 1981 .

Discovery and observation

The comet was discovered on the morning of December 18, 1980 (local time) by William A. Bradfield in Australia with 7 × 35 mm binoculars . It was his eleventh comet discovery, almost exactly a year after his last. During this period he searched for comets for a total of 113 hours. Bradfield estimated the comet's brightness to be about 6 mag. A few weeks after Bradfield's discovery, on the evening of January 5, 1981, another independent discovery was made by Marco Cavagna in Milan on his first attempt to find a comet with his 20 × 80 mm binoculars. Subsequently, the comet could already be detected on photographic recordings from July of that year.

Although the comet at the time of his discovery of the Earth seen from already close to the sun stood still continue to moving toward, he was successfully photographed on the next three days, which allowed an early calculation of its orbit. At first it could only be observed from the southern hemisphere as a quite remarkable object with 3.7 mag brightness towards the end of December.

The orbit calculations predicted great brightness for observers in the northern hemisphere a few days after it had passed the sun, but the comet did not appear high above the horizon until well into 1981. At the beginning of January, tail lengths of 5 ° and more were reported, but the brightness has already dropped significantly. An outbreak of brightness was observed in mid-January when the comet briefly appeared one magnitude brighter. A few days later, however, the brightness sank below the level of visibility with the naked eye. In connection with the outbreak of brightness, there may be some observations that suggest that the comet's core may have broken. At the end of the month the brightness was only 8 mag.

After the comet had passed the sun again towards the end of February for observers on Earth, it could not be found again until June 29th. It was observed three more times during the next two months, while its brightness decreased to about 20 mag. A final attempt to find him on September 28 with the Infrared Telescope Facility in Hawaii was unsuccessful.

The comet reached a maximum brightness of 3.5 mag, making it one of the 40 brightest comets since 1935.

Scientific evaluation

As with comet C / 1975 V1 (West) a few years earlier, photometric observations could also be made with comet Bradfield at the beginning of January 1981 in the previously unattainable situation of a phase angle of almost 150 °. Strong effects of forward scattering of sunlight could be determined, which made it possible to draw conclusions about the size of the dust particles in the cometary coma .

In the first half of January 1981, spectroscopic images of the comet in the near infrared were obtained at the Osservatorio Astrofisico di Asiago in Italy , on which a large number of spectral lines could be identified, including those of C 2 , C 3 , CH, CH + , CO + , CO 2 + , CN, N 2 + , NH, NH + , NH 2 , O, OH, OH + , H 2 O + , Hg and Na. For the first time, H 2 S + could also have been detected. The presence of emission lines of neutral carbon monoxide (CO), which previously could not be detected in brighter comets, was unusual . This may indicate a previous event in the comet's nucleus that released large amounts of CO (or its original molecule).

In the middle of the month, spectra in the ultraviolet and visible spectral range were also recorded at the Uttar Pradesh State Observatory in India , on which the spectral lines of CN, C 2 and possibly NH 2 could be detected. Despite the comet's proximity to the Sun, no sodium lines could be observed. From the observations, estimates were made of the number of CN and C 2 molecules in the comet's coma.

In early January to early March 1981, observations of the 18 cm OH emission line at Comet Bradfield were made with the Nançay radio telescope . Only a weak signal was found.

Orbit

For the comet, only a limited precise elliptical orbit could be determined from 33 observation data over a period of 405 days by Marsden , which is inclined by around 139 ° 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 December 29, 1980, it was located at a distance of about 38.9 million km from the Sun within the orbit of the planet Mercury . On October 16, the comet had already passed Mars at a distance of around 120.4 million km and on December 16 it had approached Venus within around 75.4 million km. On December 31, it reached the closest approach to earth with about 0.67  AU / 108.2 million km. On February 16, 1981, Mars passed a second time, this time at a distance of about 119.6 million km.

The comet moves in an extremely elongated elliptical orbit around the sun. Based on the currently known orbital elements, some time before the passage through the inner solar system in 1980/81, its orbit still had an eccentricity of around 0.99975 and a semi-major axis of around 1045 AU, so that its orbit period was around 34,000 years. Due to the gravitational pull of the planets, in particular due to two relatively close passages of Jupiter on December 13, 1980 in a little over 5 AU and on April 8, 1984 in about 8 ¾ AU, its orbital eccentricity was about 0.99951 and its semi-major axis to reduced by about 535 AU, so that its orbital period was shortened to about 12,400 years.

Reception in the media

On March 7, 1986, on the occasion of the return of Halley's Comet, a special stamp for 300 francs was issued in the Comoros with a digitally post-processed image of a comet and the inscription "Comète de Bradfield 1980". Comet C / 1980 Y1 may be shown, but comet C / 1979 Y1 , whose main visibility was in 1980, would also be possible.

See also

Web links

Individual evidence

  1. ^ Astronomical Society of South Australia: Comets Discovered from South Australia. Retrieved February 25, 2016 .
  2. ^ Sormano Astronomical Observatory - In memory of Marco Cavagna. June 15, 2006, accessed February 26, 2016 .
  3. ^ 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. 706-709.
  4. ^ BG Marsden: Comets in 1980 . In: Quarterly Journal of the Royal Astronomical Society , Vol. 26, 1985, pp. 156-167 ( bibcode : 1985QJRAS..26..156M ).
  5. ^ BG Marsden: Comets in 1981 . In: Quarterly Journal of the Royal Astronomical Society , Vol. 26, 1985, pp. 300-309 ( bibcode : 1985QJRAS..26R.300M ).
  6. ↑ International Comet Quarterly - Brightest comets seen since 1935. Accessed February 25, 2016 (English).
  7. ↑ RD Gehrz, EP Ney: 0.7 to 23 μm photometric observations of P / Halley 1986 III and six recent bright comets. In: Icarus. Vol. 100, 1992, pp. 162-186 doi: 10.1016 / 0019-1035 (92) 90027-5 .
  8. ↑ CB Cosmovici, C. Barbieri, C. Bonoli, F. Bortoletto, E. Hamzaoglu: On the Spectrum of Comet Bradfield 1,980 t. In: Astronomy and Astrophysics. Vol. 114, 1982, pp. 373-387 ( bibcode : 1982A & A ... 114..373C ).
  9. ↑ PS Goraya, BK Sinha, US Chaubey, BB Sanwal: Spectrophotometry of Comet Bradfield (1980t) during post-perihelion period. In: Moon and the Planets. Vol. 26, 1982, pp. 3-9 doi: 10.1007 / BF00941365 ( bibcode : 1982M & P .... 26 .... 3G ).
  10. ↑ 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 ).
  11. ↑ NASA JPL Small-Body Database Browser: C / 1980 Y1 (Bradfield). Retrieved February 25, 2016 .
  12. ↑ A. Vitagliano: SOLEX 11.0. Archived from the original on September 18, 2015 ; accessed on May 2, 2014 .
  13. ^ E. Everhart, BG Marsden: New original and future cometary orbits. In: The Astronomical Journal. Vol. 88, 1983, pp. 135-137 doi: 10.1086 / 113298 ( bibcode : 1983AJ ..... 88..135E ).
  14. ↑ Stamp World: Comores - Timbres-Poste (1986). Retrieved March 24, 2016 (French).