C / 1887 B1 (Great Southern Comet)
| C / 1887 B1 (Great Southern Comet) [i] | |
|---|---|
| Properties of the orbit ( animation ) | |
| Orbit type | parabolic |
| Numerical eccentricity | 1.0 |
| Perihelion | 0.00483 AU |
| Inclination of the orbit plane | 144.4 ° |
| Perihelion | January 11, 1887 |
| Orbital velocity in the perihelion | 606 km / s |
| history | |
| Explorer | |
| Date of discovery | January 18, 1887 |
| Older name | 1887 I, 1887a |
| Source: Unless otherwise stated, the data comes from JPL Small-Body Database Browser . Please also note the note on comet articles . | |
C / 1887 B1 (Great Southern Comet ) was a comet that could be seen with the naked eye in the southern hemisphere in 1887 . Due to its extraordinary brightness, it is counted among the " Great Comets ".
Discovery and observation
On January 11, 1887, the comet was of the earth seen from above about 22:11 UT for 35 minutes after the sun passed and on the opposite side about 20 minutes after the time of its closest approach to the sun reappeared. However, this event has not yet been observed.
John Macon Thome discovered this comet in the evening sky of January 18, 1887 (local time) in Córdoba (Argentina) , he described it as "so weak and illusory in the twilight" that he could hardly imagine it. It later emerged that the comet had been seen by a farmer and a fisherman near Blauwberg in South Africa about 6 hours earlier . A day later he was seen there in Grahamstown and Fraserburg .
The comet was observed at many observatories in the southern hemisphere until the end of January. Thome described the phenomenon as "precisely resembling the comet of 1880". On January 22nd, the comet's tail appeared as a fairly straight, pale band of light 30 to 35 ° in length, but no head of the comet could be found at the beginning of the tail. Even on the following days, when the tail length developed up to 40 °, no nucleus could be observed despite careful search . The head of the comet just appeared like a "very diffuse misty mass" separated from the tail by a gap.
On January 28, the tail was still 20 ° in length, but it faded quickly, so that it was last seen by John Tebbutt in Windsor (New South Wales) on January 30 .
The comet reached a brightness of 2 mag.
Scientific evaluation
Comets as close to the Sun as the Great South Comet of 1887 have puzzled astronomers for over 300 years. Since it was proven that the Great Comet C / 1680 V1 had almost grazed the sun's surface at a distance of only 200,000 km, they wondered on the one hand how comets can survive such a thing, and on the other hand, when such a sun streak had appeared before could.
For a long time, three or four comets from the last third of the 17th century (not the comet of 1680) were considered the most likely candidates for an earlier appearance of the Great March Comet of 1843 . Values of 175 years down to the completely impossible 7 years have been assumed as the orbital period of the comet. Direct calculations based on the observations of the comet showed, however, that the orbital period probably cannot be shorter than 400 to 500 years.
When the Great Southern Comet C / 1880 C1 appeared in 1880 , orbiting in almost the same orbit, the proponents of a 35- to 40-year period had a great time again. When the Great September Comet C / 1882 R1 reappeared with a very similar orbit in 1882 , it was already assumed that this sun streak would have been decelerated very strongly by friction in a solid medium surrounding the sun at each return. However, this turned out to be incorrect, as the observation data of the comet from 1882 showed an orbital period of several centuries.
The conclusion was that there must be a number of different comets moving in practically the same sun-grazing orbit. Daniel Kirkwood was the first to suggest in 1880 that the sun-grazing comets formed such a comet group. He suspected that the comets of 1843 and 1880 could be fragments of the comet of -371 , which, according to the report of the Greek historian Ephorus, had broken in two. The comet of 1882 also broke into several fragments as it passed the sun. A few years later, another member of this comet group was identified with the great southern comet C / 1887 B1.
The sun streaker was then examined very intensively from 1888 to 1901 by Heinrich Kreutz , who suspected that all members of the comet group later named after him, the Kreutz group , descended from an original body that broke when it passed the sun. He identified other possible members of the group, and further group members appeared in the 20th century in 1945, 1963, 1965 and 1970.
In 1967 Brian Marsden examined the orbits of the previously known comets of the Kreutz group and showed that their members can be divided into two subgroups according to their slightly different orbital elements . The sun streak C / 1887 B1, together with C / 1843 D1, is one of the representatives of subgroup I. As a result, there have been many attempts to theoretically capture the possible decay processes and resulting trajectories of the sun streaks, in particular by Zdenek Sekanina and others.
In very extensive investigations, Sekanina and Paul W. Chodas finally developed new theories about the origin and development of the Kreutz comet group, which currently reflect the current state of knowledge. According to the model of the two super fragments, it can be assumed that all the sun streakers of the Kreutz group descend from a very large predecessor comet with a diameter of almost 100 km, which may have been in the late 4th century or early 5th century a few decades before it passed the sun has broken in two roughly equal parts. The two super fragments made one more orbit around the sun and super fragment I reappeared in 1106 as the famous sun streaker X / 1106 C1 . Superfragment II appeared only a few years earlier or later, but apparently escaped observation due to unfavorable viewing conditions as there are no reports about it. Both super fragments broke into further fragments again shortly after their extremely close passage to the sun at the time, internally damaged by the enormous tidal forces ( cascading fragmentation ): Superfragment I first split into two further parts, the first appeared later as comet C / 1843 D1 , the other part disintegrated again about three years later into the two sun stripes, which appeared later as comets C / 1880 C1 and C / 1887 B1. The comet from -371, however, as it turned out, had no relation to the Kreutz group.
Orbit
For the comet, only very strongly differing orbits could initially be determined, which was due to the difficulty that no precise positions could be derived for the unobserved cometary nucleus. From existing descriptions of the tail orientation, Sekanina & Chodas succeeded in 2004 in determining a parabolic orbit from 15 observation data over 9 days . The parameters are given in the info box. The following information is based on the subsequently improved orbital elements for the comet, which were assumed by Sekanina & Chodas based on theoretical considerations and using modern mathematical methods, taking into account all planetary disturbances and relativistic effects. Then the comet described an extremely elongated elliptical orbit, which was inclined at around 144 ° to the ecliptic . The comet thus ran in the opposite sense (retrograde) like the planets through its orbit. The value for the semi-major axis was 91.7 AU and the eccentricity 0.999947. At the point of the orbit closest to the sun ( perihelion ), which the comet traversed on January 11, 1887, it was only about 26,000 km or just under 4% of a solar radius above its surface at about 0.723 million km . By December 22, 1886, it had already approached the earth to within 0.57 AU / 85.7 million km. About 44 minutes before his perihelion, he passed Venus 108.1 million km away. The nucleus of the comet dissolved shortly after its extremely close approach to the sun's surface, as only its headless tail could be observed after the comet had passed the sun .
According to the more recent investigations, the comet together with C / 1880 C1 was probably a secondary fragment of the sun-grazing comet X / 1106 C1 , after which its orbital period to its last passage through the inner solar system would have been about 780 years.
See also
Individual evidence
- ↑ a b SOLEX 11.0 by A. Vitagliano. Archived from the original on September 18, 2015 ; accessed on May 2, 2014 .
- ^ GW Kronk: Cometography - A Catalog of Comets. Volume 2: 1800-1899 . Cambridge University Press, 2003, ISBN 0-521-58505-8 , pp. 588-590.
- ^ P. Moore, R. Rees: Patrick Moore's Data Book of Astronomy . Cambridge University Press, Cambridge, 2011, ISBN 978-0-521-89935-2 , p. 270.
- ^ Daniel Kirkwood: On the Great Southern Comet of 1880. In: The Observatory. Vol. 3, No. 43, 1880, pp. 590-592 ( bibcode : 1880Obs ..... 3..590K ).
- ↑ BG Marsden: The Sungrazing Comet Group. In: The Astronomical Journal. Vol. 72, No. 9, 1967, pp. 1170-1183 ( bibcode : 1967AJ ..... 72.1170M ).
- ^ Zdeněk Sekanina: Problems of Origin and Evolution of the Kreutz Family of Sun-grazing Comets. In: Acta Universitatis Carolinae. Mathematica et Physica. Vol. 8, No. 2, 1967, pp. 33-84 ( PDF; 4.73 MB ).
- ↑ a b Zdenek Sekanina, Paul W. Chodas: Fragmentation Hierarchy of Bright Sungrazing Comets and the Birth and Orbital Evolution of the Kreutz System. I. Two-Superfragment Model. In: The Astrophysical Journal. Vol. 607, 2004, pp. 620-639 doi: /10.1086/383466 .
- ↑ Zdenek Sekanina, Paul W. Chodas: Fragmentation Hierarchy of Bright Sungrazing Comets and the Birth and Orbital Evolution of the Kreutz System. II. The Case for Cascading Fragmentation. In: The Astrophysical Journal. Vol. 663, 2007, pp. 657-676 doi: /10.1086/517490 .
- ↑ NASA JPL Small-Body Database Browser: C / 1887 B1. Retrieved on October 6, 2014 (English, the epoch given there does not match the information in Sekanina's original script, the original value from Sekanina was used for the info box).