C/1963 A1 (Ikeya)
Long-period comet discovered by Kaoru Ikeya in 1963.
C/1963 A1 (Ikeya) is a long-period comet discovered by Japanese amateur astronomer Kaoru Ikeya on 2 January 1963. At just 19 years old, Ikeya spotted the comet using a homemade 8-inch telescope, three degrees southwest of π Hydrae. It appeared diffuse, with an estimated magnitude of 12. After confirming his sighting the next day, he telegraphed the Tokyo Astronomical Observatory, and the comet was photographed with the Brashear Astrograph.
Moving rapidly southward, the comet became unobservable from the northern hemisphere after 25 January. It then became circumpolar in the southern sky, passing near the south celestial pole in Octans between 11 and 13 February, before heading north. Brightening through February, it made its closest approach to Earth on 15 February, at 0.327 AU (48.9 million km; 30.4 million mi). By 18 February, its tail stretched an estimated 8 degrees in photographs, and the comet reached third magnitude, visible to the naked eye. The tail, initially straight, grew more complex by month’s end.
The comet reappeared in the northern hemisphere by March. On 10 March, its apparent magnitude was about 4.5. By perihelion on 21 March, the tail was reported nearly 20 degrees long. After perihelion, the comet entered conjunction with the Sun and was lost to observation, reaching a minimum elongation of 4° on 12 April.
Recovered in mid-May in the morning sky, the comet was brighter than expected, fading more slowly than it had brightened, at magnitude 7 to 8. This led some to think it was a new comet, but photographs confirmed only one object, comet Ikeya. Long-exposure images in mid-June showed a tail over half a degree long. The comet faded rapidly in September and October, with its last observation on 12 October.
Spectrograms taken at Palomar Observatory on 5–6 March 1963 revealed emission lines of CN, C2, and C3. The ratio of carbon isotopes C12 to C13 was comparable to Earth’s. Additional spectra from Lick Observatory showed NH2 and a strong line at λ 6200.
The comet is considered the parent body of several meteor showers, with models predicting five streams intersecting Earth’s orbit. Two identified showers are π-Hydrids and δ-Corvids; α-Sextantids may also be linked. Another shower, θ-Leonids, detected by the Cameras for Allsky Meteor Surveillance, matches the predicted streams.
Quick Facts
- Discovery Ref
- IAUC_1812
- Discoverer
- Kaoru Ikeya
- Discovery Site
- Maisaka, Japan
- Discovery Date
- 2 January 1963
- Designations
- 1963 I, 1963aICQ1
- Orbit Ref
- jpl
- Epoch
- 26 April 1963 (JD 2438145.5)
- Observation Arc
- 278 days
- Obs
- 33
- Aphelion
- 190.5 AU
- Perihelion
- 0.632 AU
- Semimajor
- 95.55 AU
Facts from the source article.
Lore & Background
The comet was discovered by 19-year-old amateur astronomer Kaoru Ikeya using a self-made 8-inch telescope. At discovery, it was located three degrees southwest of π Hydrae, had an estimated magnitude of 12, and appeared diffuse. Ikeya confirmed his finding the next day and telegraphed the Tokyo Astronomical Observatory, after which the comet was photographed with the Brashear Astrograph. After discovery, the comet moved rapidly southwards and became circumpolar in the southern sky, passing near the south celestial pole in the constellation Octans between 11 and 13 February. It brightened through February, and on 15 February it made its closest approach to Earth at 0.327 AU. By 18 February, its tail was photographically estimated to be 8 degrees long, and the comet reached third magnitude, becoming visible to the naked eye. The tail initially had a simple straight form but grew more complex by the end of the month. By March, the comet became visible again in the northern hemisphere; on 10 March its magnitude was estimated at 4.5, and on 21 March, the date of perihelion, the tail was reported to be nearly 20 degrees long. After perihelion, the comet was in conjunction with the Sun and unobservable, reaching a minimum elongation of 4° on 12 April. It was recovered in mid-May in the morning sky, brighter than expected, with a magnitude of 7 to 8, leading some to report it as a new comet, but photographic observations confirmed it was the same object. In mid-June, long-exposure photographs showed a tail more than half a degree long. The comet faded rapidly in September and October and was last observed on 12 October.
Reader's Guide
C/1963 A1 (Ikeya) is significant as a bright long-period comet that provided valuable spectroscopic data. On 5–6 March 1963, spectrograms taken at Palomar Observatory revealed emission lines of CN, C2, and C3, and the ratio of carbon isotopes C12 to C13 was determined to be comparable to that on Earth. Additional spectra from Lick Observatory showed the presence of NH2 and a strong line at λ 6200. The comet is also notable as the parent body of several meteor showers. Modeling has shown it creates five streams that intersect Earth's orbit, two of which have been identified as π-Hydrids and δ-Corvids. The α-Sextantids may also be associated, and a meteor shower named θ-Leonids, visible in data from the Cameras for Allsky Meteor Surveillance, is a good match with predicted streams. Its legacy includes contributing to understanding of cometary composition and meteor shower origins.
Did You Know?
- At its closest approach to Earth on 15 February 1963, the comet was 0.327 AU away.
- Spectrograms taken on 5–6 March 1963 showed the carbon isotope ratio C12 to C13 was comparable to that on Earth.
- The comet is modeled to create five meteor streams, including the π-Hydrids and δ-Corvids.
More in Named Comets, Part 3 1-24
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