C / 1945 X1 (du Toit)

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C / 1945 X1 (du Toit) [i]
Properties of the orbit ( animation )
Epoch:  December 27, 1945 ( JD 2,431,817.4652)
Orbit type parabolic
s. Article text
Numerical eccentricity 1.0
Perihelion 0.0075 AU
Inclination of the orbit plane 141.9 °
Perihelion December 27, 1945
Orbital velocity in the perihelion 489 km / s
history
Explorer Daniel you Toit
Date of discovery December 11, 1945
Older name 1945 VII, 1945g
Source: Unless otherwise stated, the data comes from JPL Small-Body Database Browser . Please also note the note on comet articles .

C / 1945 X1 (du Toit) is a comet that was observed in 1945. He belongs to the Kreutz group of sun-grazing comets.

Discovery and observation

The comet was discovered by Daniel du Toit at the Harvard College Observatory in Bloemfontein shortly after midnight on December 11, 1945. He estimated its brightness to be 7 mag. In addition, he managed to make only four further observations in each of the following four nights, during which the comet was moving rapidly towards the sun .

At the beginning of January 1946, Leland E. Cunningham calculated a preliminary orbit from the observation data of du Toits , according to which the comet at midnight 27./28. December 1945, seen from Earth , must have passed behind the sun and shortly before and after it should have been "a brilliant object for the naked eye". The subsequent search on coronographic images from these days showed no signs of the comet. A search for the comet at the positions calculated by Cunningham in January 1946 was also unsuccessful.

It is not certain whether the comet did not survive its approach to the sun or whether it was only its low brightness that was the reason why it was not seen in the daytime next to the sun or later on its further orbit.

The comet reached a maximum brightness of 7 mag.

Scientific evaluation

Due to the few observations of the comet, which took place only within a short time interval, it was always difficult to derive orbital elements for the comet. After the aforementioned first calculations by Cunningham, it initially took seven years until the photo plates with the images of the comet by Albert Gray Mowbray were precisely measured. In a first investigation, Brian Marsden determined several possible parabolic orbits from this in 1967 , which were very similar to those of comets C / 1882 R1 and C / 1965 S1. In his “Catalog of Cometary Orbits” in 1986, he again gave slightly changed values, which are also mentioned in the info box. In a further investigation in 1989, Marsden also derived elliptical orbital elements under certain boundary conditions .

As early as the 19th century , several large comets had appeared that passed close to the sun like the Comet du Toit. From 1888 to 1901, the sun streakers were examined very intensively by Heinrich Kreutz , who suspected that all members of the comet group that was later named after him descended from an original body that broke when it passed in the sun. He identified comets C / 1843 D1 , C / 1880 C1 , C / 1882 R1 and C / 1887 B1 , all of which move in very similar orbits, as possible members of the group and also appeared in the 20th century after Comet du Toit further group members in the form of comets C / 1963 R1 , C / 1965 S1 and C / 1970 K1 .

Marsden had already investigated the orbits of the previously known comets of the Kreutz group in 1967 and showed that their members can be divided into two subgroups. He was able to deduce as well as proven that the comets of the Kreutz group must have been fragments of a common comet of origin, which had probably passed the sun in the first half of the 12th century . Whether this was the well-known comet X / 1106 C1 could not be proven at first. As a result, there were many attempts to theoretically capture the possible processes of decay and the resulting trajectories of the sun stripes, in particular by Zdenek Sekanina and others.

In further very extensive investigations, Sekanina and Chodas 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 II disintegrated into five further parts, the two largest of which reappeared later as comet C / 1882 R1 and C / 1965 S1, while the other three parts disintegrated into further fragments at different times. The Comet du Toit may have formed around 1700 during such a decay process.

Orbit

The following information is based on the orbital elements determined by Sekanina and Chodas in 2004 using modern mathematical methods and taking into account the gravitational influence of all planets and the relativistic effects when the comet flies close to the sun and under certain boundary conditions ("Forced elliptical solution "). The comet then runs on an elongated elliptical orbit that is inclined by around 142 ° to the ecliptic . It moves 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 passed on December 27, 1945, it was only about 0.6 solar radii above its surface at a distance of 1.11 million km from the sun . On November 20, it had already passed Mars approximately 147.2 million km, and on December 11, it had reached its closest approach to Earth with a distance of 0.62 AU / 92.6 million km. If the comet had survived the approach to the sun, a second approach to the earth would have taken place on January 16, 1946, which at 0.54 AU / 80.5 million km would have taken place a little closer than the one a month before.

According to recent research, the comet is likely a fragment of an unobserved comet that appeared in the early 12th century. According to the orbital elements determined by Sekanina under the assumption of such an origin ("Forced elliptical solution"), its orbit possibly had an eccentricity of about 0.99989 and a semiaxis of about some time before the passage of the inner solar system in 1945/46 89 AU, so that its orbital period was about 840 years.

Further intensive research is currently underway to shed more light on the fate of this comet. To this end, Sekanina and Kracht are trying to determine improved orbital elements for comet C / 1945 X1 from the few observational data of the comet and taking into account more recent findings on the sun-grazing micro comets discovered in large numbers by SOHO , also taking non-gravitational effects into account . With these improved position data, historical photo plates will be searched for further previously unknown observations of the comet. New findings in this regard would make it possible to better classify the position of the comet in the family of the sun streamer of the Kreutz group.

See also

Web links

Individual evidence

  1. ^ Gary W. Kronk : Cometography - A Catalog of Comets. Volume 4: 1933-1959 . Cambridge University Press, Cambridge 2009, ISBN 978-0-521-58507-1 , pp. 221-222.
  2. ^ Z. Sekanina: Statistical Investigation and Modeling of Sungrazing Comets Discovered with the Solar and Heliospheric Observatory. In: The Astrophysical Journal. Vol. 566, 2002, pp. 577-598 ( PDF; 715 kB ).
  3. ^ P. Moore, R. Rees: Patrick Moore's Data Book of Astronomy . Cambridge University Press, Cambridge 2011, ISBN 978-0-521-89935-2 , p. 272.
  4. ↑ See BG Marsden: The Sungrazing Comet Group. Table I.
  5. ^ A b B. G. Marsden: The Sungrazing Comet Group. In: The Astronomical Journal. Vol. 72, No. 9, 1967, pp. 1170-1183 ( bibcode : 1967AJ ..... 72.1170M ).
  6. ↑ See BG Marsden: The Sungrazing Comet Group. II. Table IV.
  7. ↑ NASA JPL Small-Body Database Browser: C / 1945 X1. Retrieved October 21, 2015 .
  8. ↑ BG Marsden: The Sungrazing Comet Group. II. In: The Astronomical Journal. Vol. 98, No. 6, 1989, pp. 2306-2321 ( bibcode : 1989AJ ..... 98.2306M ).
  9. ^ Z. 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 ).
  10. ↑ a b c Z. Sekanina, PW 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 ( PDF; 331 kB ).
  11. ↑ Z. Sekanina, PW 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 ( PDF; 551 kB ).
  12. ↑ SOLEX 11.0 A. Vitagliano. Archived from the original on September 18, 2015 ; accessed on May 2, 2014 .
  13. ↑ Z. Sekanina, R. Kracht: Was Comet C / 1945 X1 (you Toit) a Dwarf, SOHO-Like Kreutz Sungrazer? Version 2 of September 11, 2015, pp. 1–22 (Accepted for publication in: The Astrophysical Journal. ) ( Arxiv : 1506.01402 ).