9142 Rhesus (// REE-səs), provisional designation 5191 T-3, is a larger Jupiter trojan from the Trojan camp, approximately 42 kilometers (26 miles) in diameter. It was discovered during the third Palomar–Leiden Trojan survey in 1977, and later named after King Rhesus from Greek mythology. The dark D-type asteroid has a rotation period of 7.3 hours.
|Discovered by||C. J. van Houten|
I. van Houten-G.
|Discovery site||Palomar Obs.|
|Discovery date||16 October 1977|
|MPC designation||(9142) Rhesus|
|Pronunciation||// · REE-səs|
|Rhesus of Thrace |
|5191 T-3 · 1988 RX|
|Jupiter trojan |
Trojan  · background 
|Orbital characteristics |
|Epoch 23 March 2018 (JD 2458200.5)|
|Uncertainty parameter 0|
|Observation arc||63.18 yr (23,076 d)|
|11.76 yr (4,295 d)|
|0° 5m 1.68s / day|
|Jupiter MOID||0.4321 AU|
Rhesus was discovered on 16 October 1977, by Dutch astronomer couple Ingrid and Cornelis van Houten at Leiden, on photographic plates taken by Dutch–American astronomer Tom Gehrels at the Palomar Observatory in California. The body's observation arc begins with its first observation, a precovery taken at Palomar in December 1954.
The survey designation "T-3" stands for the third Palomar–Leiden Trojan survey, named after the fruitful collaboration of the Palomar and Leiden Observatory in the 1960s and 1970s. Gehrels used Palomar's Samuel Oschin telescope (also known as the 48-inch Schmidt Telescope), and shipped the photographic plates to Ingrid and Cornelis van Houten at Leiden Observatory where astrometry was carried out. The trio are credited with the discovery of several thousand asteroids.
Orbit and classificationEdit
Rhesus is a dark Jovian asteroid in a 1:1 orbital resonance with Jupiter. It is located in the trailering Trojan camp at the Gas Giant's L5 Lagrangian point, 60° behind its orbit . It orbits the Sun at a distance of 4.5–5.8 AU once every 11 years and 9 months (4,295 days; semi-major axis of 5.17 AU). Its orbit has an eccentricity of 0.13 and an inclination of 13° with respect to the ecliptic.
This minor planet was named from Greek mythology after King Rhesus of Thrace an ally of the Trojans against the Greeks in the Trojan War. He was killed in his sleep by Odysseus and Diomedes who attacked the Thracian camp in the dead of night. The official naming citation was published by the Minor Planet Center on 8 December 1998 (M.P.C. 33389).
In August 2012, and September 2013, two rotational lightcurves of Rhesus were obtained from photometric observations in the R-band by astronomers at the Palomar Transient Factory in California. Lightcurve analysis gave a rotation period of 7.325±0.0021 and 7.284±0.0087 hours with a brightness amplitude of 0.27 and 0.24 magnitude, respectively (U=2/2).
Diameter and albedoEdit
According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Rhesus measures 42.31 kilometers in diameter and its surface has an albedo of 0.062, while the Collaborative Asteroid Lightcurve Link assumes a standard albedo for a carbonaceous asteroid of 0.057 and calculates a shorter diameter of 34.85 kilometers based on an absolute magnitude of 11.02.
- "9142 Rhesus (5191 T-3)". Minor Planet Center. Retrieved 25 June 2018.
- "JPL Small-Body Database Browser: 9142 Rhesus (5191 T-3)" (2018-02-25 last obs.). Jet Propulsion Laboratory. Retrieved 25 June 2018.
- "List of Jupiter Trojans". Minor Planet Center. 1 June 2018. Retrieved 25 June 2018.
- "Asteroid (9142) Rhesus – Proper Elements". AstDyS-2, Asteroids – Dynamic Site. Retrieved 25 June 2018.
- Grav, T.; Mainzer, A. K.; Bauer, J. M.; Masiero, J. R.; Nugent, C. R. (November 2012). "WISE/NEOWISE Observations of the Jovian Trojan Population: Taxonomy". The Astrophysical Journal. 759 (1): 10. arXiv:1209.1549. Bibcode:2012ApJ...759...49G. doi:10.1088/0004-637X/759/1/49. Retrieved 25 June 2018. (online catalog)
- "LCDB Data for (9142) Rhesus". Asteroid Lightcurve Database (LCDB). Retrieved 25 June 2018.
- Waszczak, Adam; Chang, Chan-Kao; Ofek, Eran O.; Laher, Russ; Masci, Frank; Levitan, David; et al. (September 2015). "Asteroid Light Curves from the Palomar Transient Factory Survey: Rotation Periods and Phase Functions from Sparse Photometry" (PDF). The Astronomical Journal. 150 (3): 35. arXiv:1504.04041. Bibcode:2015AJ....150...75W. doi:10.1088/0004-6256/150/3/75. Retrieved 25 June 2018.
- Veres, Peter; Jedicke, Robert; Fitzsimmons, Alan; Denneau, Larry; Granvik, Mikael; Bolin, Bryce; et al. (November 2015). "Absolute magnitudes and slope parameters for 250,000 asteroids observed by Pan-STARRS PS1 - Preliminary results" (PDF). Icarus. 261: 34–47. arXiv:1506.00762. Bibcode:2015Icar..261...34V. doi:10.1016/j.icarus.2015.08.007. Retrieved 25 June 2018.
- "Asteroid 9142 Rhesus". Small Bodies Data Ferret. Retrieved 25 June 2018.
- Carvano, J. M.; Hasselmann, P. H.; Lazzaro, D.; Mothé-Diniz, T. (February 2010). "SDSS-based taxonomic classification and orbital distribution of main belt asteroids". Astronomy and Astrophysics. 510: 12. Bibcode:2010A&A...510A..43C. doi:10.1051/0004-6361/200913322. Retrieved 25 June 2018.
- "Minor Planet Discoverers (by number)". Minor Planet Center. 31 May 2018. Retrieved 25 June 2018.
- "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 25 June 2018.
- Asteroid Lightcurve Database (LCDB), query form (info)
- Dictionary of Minor Planet Names, Google books
- Discovery Circumstances: Numbered Minor Planets (5001)-(10000) – Minor Planet Center
- 9142 Rhesus at AstDyS-2, Asteroids—Dynamic Site
- 9142 Rhesus at the JPL Small-Body Database