C/1961 T1 (Seki)
Long-period comet parent of December ρ-Virginids meteor shower.
C/1961 T1 (Seki) is a long-period comet that serves as the parent body of the December ρ-Virginids meteor shower. It was discovered by Tsutomu Seki on 10 October 1961.
Seki spotted the comet from Kochi, Japan, using a 9-cm refractor while sweeping the southeastern sky before twilight. The comet lay 10 degrees above the horizon in Leo, with an estimated magnitude of 7–8. It was then at perihelion and at an elongation of 31 degrees. Minoru Honda confirmed the sighting on 11 October, describing the comet as diffuse with central concentration and a magnitude of 8. On 14 October, the comet reached its northernmost declination of 14° north; that day Ahnert reported a tail 4 degrees long, and George Alcock gave an apparent magnitude of 7. Elias and Phocas, observing from Athens Observatory, noted the nucleus had split into three parts on 17 October, and bright condensations appeared around it on 19 October. On 25 October, Elizabeth Roemer estimated the comet’s apparent magnitude at 6.5 using binoculars.
The comet brightened in November as it approached Earth and moved rapidly southward. It was first reported visible to the naked eye on 11 November, with brightness estimates between 4.5 and 5.5. On 15 November 1961, the comet came within 0.102 AU of Earth. S. Archer from Rhodes University, South Africa, estimated its peak apparent magnitude at 4.3 and its coma up to 40 arcminutes across. John Caister Bennett gave an apparent magnitude of 4 on 13 and 15 November. The comet reached its southernmost declination of -69° on 16 November. It then faded quickly; on 4 December its magnitude was reported as 8.4, and it was last detected on 29 December 1961.
Because the comet approaches Earth to within 0.08 AU, it was suggested as early as 1961 that it could produce meteors. Mathematical models show its meteor stream evolved into two filaments. One filament produces the December ρ-Virginids shower, and the other the γ-Sagittariids.
Quick Facts
- Discoverer
- Tsutomu Seki
- Discovery Date
- 10 October 1961
- Designations
- 1961f / 1961 VIII
- Orbit Ref
- jpl
- Epoch
- 12 November 1961 (JD 2437615.5)
- Observation Arc
- 75 days
- Obs
- 15
- Aphelion
- 173 AU
- Perihelion
- 0.681 AU
- Semimajor
- 86.8 AU
- Eccentricity
- 0.9921
- Period
- ~810 years
Facts from the source article.
Lore & Background
The comet was discovered on 10 October 1961 by Tsutomu Seki from Kochi, Japan, using a 9-cm refractor. He spotted it 10 degrees above the horizon in the constellation of Leo, estimating its magnitude at 7–8. The comet was then at perihelion and at an elongation of 31 degrees. Confirmation came from Minoru Honda on 11 October, who described it as diffuse with central concentration and magnitude 8. On 14 October, the comet reached its northernmost declination at 14° north, with Ahnert reporting a tail 4 degrees long and George Alcock estimating magnitude 7. Elias and Phocas at Athens Observatory noted the nucleus split into three on 17 October, with bright condensations around it on 19 October. Elizabeth Roemer estimated magnitude 6.5 on 25 October using binoculars.
The comet brightened in November as it approached Earth and moved rapidly southwards. First reported naked-eye on 11 November, brightness estimates ranged from 4.5 to 5.5. It approached Earth to 0.102 AU on 15 November. S. Archer from Rhodes University, South Africa, estimated peak magnitude 4.3 and a coma up to 40 arcminutes across. John Caister Bennett estimated magnitude 4 on 13 and 15 November. The comet reached its southernmost declination of -69° on 16 November, then faded quickly, with magnitude 8.4 reported on 4 December. It was last detected on 29 December 1961.
Reader's Guide
C/1961 T1 (Seki) holds significance as the identified parent body of the December ρ-Virginids meteor shower, a connection suggested from 1961 due to the comet's approach to Earth within 0.08 AU. Mathematical models indicate the comet's meteor stream evolved into two filaments, with the first filament linked to the December ρ-Virginids and the second to the γ-Sagittariids. The comet's discovery by Tsutomu Seki using a 9-cm refractor, its rapid brightening to naked-eye visibility, and its close approach of 0.102 AU on 15 November 1961 contributed to its observational interest. The splitting of its nucleus on 17 October, observed by Elias and Phocas, added to its legacy as a dynamically active comet. Its legacy is primarily tied to its role as a meteor shower parent, with the December ρ-Virginids being the direct result of its debris stream.
Did You Know?
- The comet was discovered by Tsutomu Seki on 10 October 1961 using a 9-cm refractor.
- Its nucleus split into three parts on 17 October 1961, observed from Athens Observatory.
- The comet approached Earth to a distance of 0.102 AU on 15 November 1961.
More in Named Comets, Part 3 1-24
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