C / 1965 S1 (Ikeya-Seki)

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C / 1965 S1 (Ikeya-Seki) [i]
Comet Ikeya-Seki on October 30th with a fully developed tail
Comet Ikeya-Seki on October 30th with a fully developed tail
Properties of the orbit ( animation )
Epoch:  October 7, 1965 ( JD 2,439,040.5)
Orbit type long-period
Numerical eccentricity 0.999915
Perihelion 0.0078 AU
Aphelion 183.2 AU
Major semi-axis 91.6 AU
Sidereal period ~ 880 a
Inclination of the orbit plane 141.9 °
Perihelion October 21, 1965
Orbital velocity in the perihelion 477 km / s
history
Explorer K. Ikeya , T. Seki
Date of discovery September 18, 1965
Older name 1965 VIII, 1965f
Source: Unless otherwise stated, the data comes from JPL Small-Body Database Browser . Please also note the note on comet articles .

C / 1965 S1 (Ikeya-Seki) ( Japanese 池 谷 ・ 関 彗星 Ikeya-Seki-suisei ) was a comet that could be seen with the naked eye during the day in 1965 . It was the brightest comet of the 20th century and is counted among the " Great Comets " due to its extraordinary brightness .

Discovery and observation

When the comet was independently discovered on the morning of September 18, 1965 by the two astronomers Kaoru Ikeya and Tsutomu Seki as a foggy spot with an inconspicuous brightness of 7 to 8 mag, nothing indicated its grandiose development. Both Ikeya and Seki had already discovered two comets each and were due to share another discovery at the end of 1967. Their discovery was confirmed a day later by an observatory in Australia .

Initial orbital calculations initially indicated an unexciting perihelion distance in the area of ​​Earth orbit, but after further measurements of the comet's positions it became clear that the initial assumption was far from being. Towards the end of September, after more precise orbital determinations by Brian Marsden, it became clear that it was another sunstreaker of the Kreutz group with a similar orbit as the Great September Comet C / 1882 R1 .

The brightness of the comet increased from day to day and on September 26th a tail of 1.5 ° length was photographed for the first time . From the end of September the comet could also be observed with the naked eye. From the beginning to the middle of October the brightness had already increased from about 6 mag to about 1 mag and the length of the tail reached 5 °.

The comet reached a brightness of 2 mag on October 14, 1965 . On October 20, the comet could be seen with the naked eye in the daytime for the first time. Gérard-Henri de Vaucouleurs was able to see it at an observatory in Texas at noon only 2 ° next to the sun with a brightness of -10 mag (also the maximum value of the comet) and a 1 to 2 ° long tail. Elizabeth Roemer in Flagstaff and other observers in New Mexico confirmed this information.

While the comet continued to strive towards its closest point to the sun, it was observed by numerous observers around the world in the daytime sky, many were able to photograph it with simple cameras as long as the sun was only covered. On October 21, it passed the sun at a distance of 0.3 ° from Earth and reached its northernmost declination . One day after passing the perihelion, the comet was still very bright with about -3 mag.

During the last days of October and the first days of November, tail lengths of up to 30 ° (which corresponded to a real length of 0.75 AU ) were generally reported. One observer even claims to have seen a 45 ° long tail on the morning of October 28th. At this time, a second plasma tail was also observed next to the bright dust tail. The condensation (striae) in the dust tail gave it a characteristic corkscrew shape.

A double cometary nucleus was observed for the first time on November 4th . In addition to the main nucleus, a weaker second nucleus was found, which could then be observed until January 14, 1966. It is rather uncertain whether there was a third fragment. Zdenek Sekanina retrospectively determined October 21 as the probable date for the breakage of the core, as well as a mass ratio between fragments A and B of about 15: 1.

In the southern hemisphere, the comet could be observed with the naked eye for the whole of November. Towards the end of November a brightness of 3 mag and a tail length of 30 ° were reported. After that, the comet faded very quickly, because the tail could still be observed at first, but had already disappeared by mid-December. The last visual observation of the comet took place on January 31, 1966 at a brightness of 11 mag, it may also have been photographed for the last time on February 12. Later attempts to capture the comet in images were unsuccessful.

Scientific evaluation

The spectrum of the comet was observed by numerous researchers all over the world from late October through November. In the spectrograms , in addition to the usual emission lines of comets around the time of the perihelion, particularly prominent lines of sodium , iron and ionized calcium were found. In addition, measurements of the microwave spectrum were carried out with a radio telescope .

Investigations of the comet's polarization and infrared radiation have also been undertaken. From 23 to 26 October, the comet was in Hawaii and from 40,000 feet altitude of an airplane Convair CV-990 of NASA from photographs, make measurements to the tail.

The comet belongs to the group of sun streaks , which are comets that pass extremely close to the sun. Several such comets had already been observed in the 19th century , including the Great March Comet C / 1843 D1 , the Great South Comet C / 1880 C1 , the Great September Comet C / 1882 R1 and the Great South Comet C / 1887 B1 .

Comet Ikeya-Seki as seen from Canberra on October 31, 1965. Drawing by David Nicholls.

From 1888 to 1901, the sun streakers were examined very intensively by Heinrich Kreutz , who suspected that all members of the group of comets, later named after him, the Kreutz group , descended from an original body that broke while walking in the sun. Even in the 20th century , other group members appeared in 1945, 1963, 1965 (with this comet) 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. The comet C / 1965 S1 (Ikeya-Seki) belongs together with C / 1882 R1 to the most important representatives of the subgroup II. From the similarity of the orbital elements with the comet C / 1882 R1 he deduced as well as proven that both Comets were still a body when they last passed the Sun in the first half of the 12th century . Whether this could have been the well-known comet X / 1106 C1 , however, could not be proven. 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 2002 Sekanina and Paul W. Chodas examined the possible decay process of the comet of 1106 in more detail. By comparing the orbital elements of the two sun stripes from 1882 and 1965, they were able to confirm Marsden's assumption that they have a common origin and that they must have divided about 18 days after the perihelion of their original comet, when it was already 0.75 AU from the sun was removed.

In very extensive investigations, Sekanina & 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 that time, internally damaged by the enormous tidal forces ( cascading fragmentation ): Superfragment II disintegrated into at least three further parts, the largest reappeared later as comet C / 1882 R1, another part appeared as the comet C / 1965 S1 (Ikeya-Seki) and the third part (partly after further decay processes) was the source of the other sun-grazing comets that appeared in 1945, 1963 and 1970.

Orbit

Brian Marsden was able to calculate orbital elements for the two fragments of the comet after they had split . The orbital elements calculated by Marsden for the larger fragment A are given in the info box.

Comet Ikeya-Seki

Until the comet breaks up shortly after its perihelion passage, the following information is based on the orbital elements for the comet's center of mass, which Sekanina & Chodas developed in 2002 based on theoretical considerations about the orbit before and after the decay of the comet's nucleus and using modern mathematical methods Consideration of all planetary disturbances and relativistic effects were assumed. The track elements for the two fragments A and B are then used. According to this, the comet described an extremely elongated elliptical orbit before its decay , which was inclined at around 142 ° 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 92.5 AU and the eccentricity 0.999916. At the point of the orbit closest to the sun ( perihelion ), which the comet traversed on October 21, 1965, it was only ⅔ of a solar radius above its surface at about 1.165 million km from the sun . Already on October 17th it had approached the earth within 0.91 AU / 135.6 million km and 3 ½ hours before its perihelion of Venus up to 106.8 million km. After the comet's decay, the two fragments passed the earth again on November 26th at a distance of 1.05 AU / 156.5 million km (A) and 156.6 million km (B), respectively.

According to recent studies, the comet is likely a fragment of an unobserved comet that appeared in the early 12th century; accordingly its orbital period up to its last passage through the inner solar system would have been about 860 years. The next perihelion of the fragments will possibly take place around the year 2760 (A) and 2910 (B).

Reception in the media

In the Republic of Congo was one on 17 February 1986 Airmail - special stamp to 225 CFA francs with a picture of the comet Ikeya-Seki occasion of the publication of Halley's Comet edited.

See also

Web links

Commons : C / 1965 S1 (Ikeya-Seki)  - collection of images, videos and audio files

Individual evidence

  1. ^ Donald K. Yeomans: NASA JPL Solar System Dynamics: Great Comets in History. Retrieved June 17, 2014 .
  2. ^ P. Moore, R. Rees: Patrick Moore's Data Book of Astronomy . Cambridge University Press, Cambridge 2011, ISBN 978-0-521-89935-2 , p. 271.
  3. ↑ a b c Zdenek Sekanina, Paul W. Chodas: Common Origin of Two Major Sungrazing Comets. In: The Astrophysical Journal. Vol. 581, 2002, pp. 760-769 doi: 10.1086 / 344216 .
  4. ^ A b Gary W. Kronk , Maik Meyer : Cometography - A Catalog of Comets. Volume 5: 1960-1982 . Cambridge University Press, Cambridge 2010, ISBN 978-0-521-87226-3 , pp. 146-155.
  5. ^ DAJ Seargent: The Greatest Comets in History: Broom Stars and Celestial Scimitars . Springer, New York 2009, ISBN 978-0-387-09512-7 , pp. 219-224.
  6. ^ Peter Grego: Blazing a Ghostly Trail: ISON and Great Comets of the Past and Future . Springer, Cham 2013, ISBN 978-3-319-01774-7 , pp. 133-134.
  7. ↑ MKV Bappu, KR Sivaraman, A. Bhatnagar, V. Natarajan: Monochromatic Polarization Measures of Comet Ikeya-Seki (1965f). In: Monthly Notices of the Royal Astronomical Society. Vol. 136, 1967, pp. 19-25 ( bibcode : 1967MNRAS.136 ... 19B ).
  8. ↑ EE Becklin, JA Westphal: Infrared Observations of comet 1965f. In: The Astrophysical Journal. Vol. 145, 1966, pp. 445-453 ( bibcode : 1966ApJ ... 145..445B ).
  9. ↑ LC Hagughney, M. Bader, R. Innes: Airborne photographic observations of Comet Ikeya-Seki 1965 VIII. In: The Astronomical Journal. Vol. 72, No. 9, 1967, pp. 1166-1169 ( bibcode : 1967AJ ..... 72.1166H ).
  10. ↑ BG Marsden: The Sungrazing Comet Group. In: The Astronomical Journal. Vol. 72, No. 9, 1967, pp. 1170-1183 ( bibcode : 1967AJ ..... 72.1170M ).
  11. ^ 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 ).
  12. ↑ 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 .
  13. ↑ 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 .
  14. ↑ NASA JPL Small-Body Database Browser: C / 1965 S1-A. Retrieved October 13, 2014 .
  15. ↑ SOLEX 11.0 A. Vitagliano. Archived from the original on September 18, 2015 ; accessed on May 2, 2014 .
  16. ^ Colnect. Retrieved October 16, 2014 .