 Comet Arend–Rigaux imaged byGeorge van Biesbroeck from theYerkes Observatory on 10 February 1951.[1] | |
| Discovery[2] | |
|---|---|
| Discovered by | Sylvain Arend Fernand Rigaux |
| Discovery site | Royal Observatory of Belgium |
| Discovery date | 5 February 1951 |
| Designations | |
| P/1951 C2, P/1958 B1 | |
| |
| Orbital characteristics[4][5] | |
| Epoch | 5 May 2025 (JD 2460800.5) |
| Observation arc | 74.31 years |
| Earliestprecovery date | 8 January 1951 |
| Number of observations | 4,700 |
| Aphelion | 5.709 AU |
| Perihelion | 1.431 AU |
| Semi-major axis | 3.570 AU |
| Eccentricity | 0.59906 |
| Orbital period | 6.745 years |
| Inclination | 19.059° |
| 118.79° | |
| Argument of periapsis | 332.93° |
| Mean anomaly | 3.564° |
| Last perihelion | 10 April 2025 |
| Next perihelion | 2032-Jan-08[3] |
| TJupiter | 2.711 |
| EarthMOID | 0.466 AU |
| JupiterMOID | 0.154 AU |
| Physical characteristics[6][7] | |
Mean radius | 4.24 km (2.63 mi) |
| 13.452 hours | |
| 0.028 | |
| Comet total magnitude (M1) | 13.9 |
49P/Arend–Rigaux is aperiodic comet with a 6.75-year orbit around theSun. It is the first of three comets discovered by Belgian astronomerSylvain Arend and the only one forFernand Rigaux.
While on a routine search for new asteroids in the sky,Sylvain Arend andFernand Rigaux discovered a new comet on the night of 5 February 1951.[8] It was a diffuse 11th-magnitude object within the constellationCanis Minor.[a]
The first physical measurements of itsnucleus in 1985 revealed that it has a geometric albedo of 0.028, placing it as one of the darkest objects in the Solar System,[9] which is even compared toD-type asteroids andC/1983 H1.[10] These initial measurements suggest that the nucleus is elongated and has an effective radius between 3.8–5.1 km (2.4–3.2 mi).[10] Photometry of direct thermal emission taken in the same year suggested a nuclear radius of 4.8 ± 0.4 km (2.98 ± 0.25 mi).[11] In 2004, a definitive radii measurement based on previous studies found that the nucleus is 4.24 km (2.63 mi) across.[6]
InitialCCD photometry taken during its 1984/1985 apparition revealed a cyclic variation in the comet's brightness indicating a rotation period between6.78±0.08 to9.78±0.08 hours.[12] This is later revised to 13.47 hours following the reanalysis of narrow-band photometry in visible and near-ultraviolet spectrum.[13] Follow-up observations during its 2012 apparition found it has a double-peaked lightcurve change, which revealed it has a retrograde synodic rotation period lasting 13.452 hours instead.[7]
Analysis of infrared observations fromSpitzer obtained in 2006 combined with ground observations in 2012 revealed a broad tail-like feature and a narrow jet emitting subsurface volatiles,[14] specifically amorphous water ice, that have recently been exposed by comet's multiple passes from the Sun.[15]
As of 2025[update], comet Arend–Rigaux orbits theSun at distances between 1.43 AU (214 million km) and 5.71 AU (854 million km), inclined about 19 degrees from the ecliptic.[5]
The first orbital calculations for Arend–Rigaux were taken byJoseph L. Brady andNevin Sherman on 19 February 1951.[16][17]Leland E. Cunningham noted that the comet's preliminary orbit somewhat resembles that of69P/Taylor, which was alost comet at the time.[18] In 1954,Vitaly A. Bronshten hypothesized that Arend–Rigaux is one of two fragments of comet Taylor, with the second one returning asD/1952 B1 (Harrington–Wilson) a year later after 49P.[19] However, the connection between the two comets were later disproven, and comet Taylor itself would not be rediscovered until 1977.[20]
On 20 December 2058 the comet will pass 0.0867 AU (12.97 million km) fromMars.[4]
| Numbered comets | ||
|---|---|---|
| Previous 48P/Johnson | 49P/Arend–Rigaux | Next 50P/Arend |
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