61P/Shajn–Schaldach

61P/Shajn-Schaldach
	Comet Shajn–Schaldach photographed from the Zwicky Transient Facility on 19 October 2022.
Discovery
Discovered by	Pelageja F. Shajn; Robert D. Schaldach
Discovery site	Simeiz Observatory, USSR; Lowell Observatory, USA
Discovery date	18–20 September 1949
Designations
MPC designation	P/1949 S1, P/1971 S2
Alternative designations	1949 VI, 1971 IX, 1979 I; 1986 X, 1993 XVII; 1949e, 1971e, 1978i; 1985i, 1993k;
Orbital characteristics
Epoch	21 November 2025 (JD 2461000.5)
Observation arc	74.39 years
Number of; observations	2,805
Aphelion	5.252 AU
Perihelion	2.130 AU
Semi-major axis	3.691 AU
Eccentricity	0.42286
Orbital period	7.091 years
Inclination	5.996°
Longitude of; ascending node	162.96°
Argument of; periapsis	221.72°
Mean anomaly	156.34°
Last perihelion	23 October 2022
Next perihelion	25 November 2029
TJupiter	2.927
Earth MOID	1.133 AU
Jupiter MOID	0.306 AU
Physical characteristics
Mean radius	0.61 ± 0.03 km (0.379 ± 0.019 mi)
Mean density	490±60 kg/m3
Synodic rotation period	4.9 hours
Comet total; magnitude (M1)	11.9
Comet nuclear; magnitude (M2)	15.4

Comet Shajn–Schaldach, also known as 61P/Shajn–Schaldach, is a Jupiter-family comet with a 7.09-year orbit around the Sun.^[7] It is the only comet discovered by Pelageja F. Shajn and Robert D. Schaldach.

Observational history

It was discovered on 18 September 1949 on a photographic plate by Pelageja F. Shajn at the Simeiz Observatory, Crimea, part of the Crimean Astrophysical Observatory. It was also discovered independently two days later by Robert D. Schaldach at the Lowell Observatory in Arizona, US, also on a photographic plate. Shajn then found evidence of the comet on earlier photographs taken on August 28 and September 4.

The first computations of the comet's orbit gave a perihelion date of between December 1949 and October 1950 with a periodicity of 7.76 years. After taking into account perturbations due a close approach to Jupiter the next perihelion was calculated to be on 15 March 1957 but in that year it was never found. It was also not discovered on its next predicted appearance in 1964. The most likely explanation for the two failures was the comet's faintness.

It was, however, re-located on 29 September 1971 by Charles T. Kowal of the Department of Astrophysics, California Institute of Technology, US, using the 122 cm Palomar Schmidt telescope, who estimated its brightness at a faint magnitude of 16. Other astronomers confirmed the sighting.

The comet was successfully observed on its subsequent returns in 1979, 1986, 1993, 2001 and 2008.

Physical characteristics

Based on observations by the Hubble Space Telescope the nucleus of the comet has an effective radius of 0.61 ± 0.03 km (0.379 ± 0.019 mi).^[4]

Notes

↑ Observation arc from the Minor Planet Center database only covered dates from 26 September 1949 until 9 February 2024 (74.37 years). This figure includes its entire arc up to 18 September 1949.