 Comet Ikeya 1963a next toα Piscium on 14 March 1963 | |
| Discovery[1] | |
|---|---|
| Discovered by | Kaoru Ikeya |
| Discovery site | Maisaka, Japan |
| Discovery date | 2 January 1963 |
| Designations | |
| 1963a[2] 1963 I | |
| Orbital characteristics[3] | |
| Epoch | 26 April 1963 (JD 2438145.5) |
| Observation arc | 278 days |
| Number of observations | 33 |
| Aphelion | 190.5 AU |
| Perihelion | 0.632 AU |
| Semi-major axis | 95.55 AU |
| Eccentricity | 0.99338 |
| Orbital period | 934 years |
| Inclination | 160.64° |
| 53.22° | |
| Argument of periapsis | 336.30° |
| Last perihelion | 21 March 1963 |
| TJupiter | –0.874 |
| EarthMOID | 0.2364 AU |
| JupiterMOID | 0.5942 AU |
| Physical characteristics[4] | |
| Comet nuclear magnitude (M2) | 15.0 |
| 2.8 (1963 apparition) | |
C/1963 A1 (Ikeya), also known asComet 1963I and1963a, is a long periodcomet discovered byKaoru Ikeya on 2 January 1963. The comet last passed perihelion on 21 March 1963, when it reached anapparent magnitude of 2.8.[4]
The comet was discovered by the Japanese amateur astronomerKaoru Ikeya on 2 January 1963. At that time Kaoru Ikeya was 19 years old and used a self-made 8-inch telescope. The comet was then located three degrees southwest ofπ Hydrae,[a] had an estimated magnitude of 12 and was diffuse. He confirmed his finding the next day and telegraphed his discovery to theTokyo Astronomical Observatory,[1] and the new comet was photographed with the Brashear Astrograph.[6]
The comet at discovery was moving rapidly southwards and after 25 January could not be observed from the northern hemisphere.[6] The comet became circumpolar in the southern sky and between February 11 and February 13 was in the constellation ofOctans, near the south celestial pole, and then moved northwards.[5] The comet was brightening during February and 15 February was the day of theclosest approach of the comet to Earth, at a distance of 0.327 AU (48.9 million km; 30.4 million mi). The comet grew a tail that photographically was estimated to be 8 degrees long on February 18, while it reached third magnitude and was visible withnaked eye. The tail originally had a simple straight form but its structure became more complex by the end of the month.[7]
By March 1963 the comet again became visible in the northern hemisphere. By March 10 the apparent magnitude of the comet was estimated to be 4.5.[7] The length of the tail was reported to be as long as nearly 20 degrees on 21 March, the date of the perihelion.[5] After perihelion the comet was inconjunction with the Sun and could not be observed.[7] It reached its minimumelongation of 4° on 12 April.[5]
The comet was recovered in mid-May in the morning sky and was brighter than expected, as the comet faded at a slower rate than it brightened, having a magnitude of 7 to 8. The brighter than expected comet led to some reports that this was a new comet, but photographic observations revealed that there was only one comet in the region, comet Ikeya. In long exposure photographs in mid-June the tail was more than half a degree long.[8] The comet faded rapidly in September and October and was last observed on 12 October.[9]
On March 5 and 6, 1963,spectrograms of the comet could be taken at thePalomar Observatory in California, showing the emission lines of CN, C2 and C3. The ratio of theisotopes12C/13C could be determined from the intensities. The value was in a range comparable to that on Earth.[10] The spectrum obtained fromLick Observatory showed the presence ofdiatomic carbon and NH2 and also featured a strong line in λ 6200.[11]
The comet is considered to be the parent body of a number ofmeteor showers, as it has been modeled to create five streams that intersect with the orbit of Earth. Two of these meteor showers have been identified as π-Hydrids and δ-Corvids. Also the meteor shower of α-Sextantids could also be associated with comet Ikeya. One more meteor shower visible in the data of the Cameras for Allsky Meteor Surveillance, named θ-Leonids is also a good match with the predicted meteor streams.[12]
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