2594 Acamas

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2594 Acamas
Discovery [1]
Discovered byC. Kowal
Discovery sitePalomar Obs.
Discovery date4 October 1978
MPC designation(2594) Acamas
Pronunciation/ˈækəməs/ · AK-ə-məs
Named after
Acamas (Greek mythology)[1]
1978 TB · 1977 RR
Jupiter trojan[1][2]
Trojan[3] · background[4]
Orbital characteristics[2]
Epoch 23 March 2018 (JD 2458200.5)
Uncertainty parameter 0
Observation arc64.44 yr (23,537 d)
Aphelion5.4911 AU
Perihelion4.6313 AU
5.0612 AU
11.39 yr (4,159 d)
0° 5m 11.76s / day
Jupiter MOID0.082 AU
Physical characteristics
Mean diameter
25.87±0.59 km[5]
25.954±0.0468 h (R)[6][7]
C (assumed)[6]

2594 Acamas (/ˈækəməs/ AK-ə-məs), provisional designation 1978 TB, is a mid-sized Jupiter trojan from the Trojan camp, approximately 25 kilometers (16 miles) in diameter. It was discovered on 4 October 1978, by American astronomer Charles Kowal at the Palomar Observatory in California.[1] The dark Jovian asteroid has a longer-than average rotation period of 26 hours and possibly an elongated shape.[6] It was named after the Thracian leader Acamas from Greek mythology.[1]

Orbit and classification[edit]

Acamas 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 on its orbit (see Trojans in astronomy). It is also a non-family asteroid of the Jovian background population.[4]

It orbits the Sun at a distance of 4.6–5.5 AU once every 11 years and 5 months (4,159 days; semi-major axis of 5.06 AU). Its orbit has an eccentricity of 0.08 and an inclination of 6° with respect to the ecliptic.[2] The body's observation arc begins with a precovery taken at Palomar in September 1953, or 25 years prior to its official discovery observation.[1]

Physical characteristics[edit]

Acamas is an assumed, carbonaceous C-type asteroid, while most larger Jupiter trojans are D-type asteroids.[6]

Rotation period[edit]

In September 2013, a rotational lightcurve of Acamas was obtained from photometric observations in the R-band by astronomers at the Palomar Transient Factory in California. Lightcurve analysis gave a rotation period of 25.954±0.0468 hours with a brightness amplitude of 0.50 magnitude (U=2).[6][7] A high brightness variation typically indicates that the body has an elongated rather than spherical shape.

Diameter and albedo[edit]

According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Acamas measures 25.87 kilometers in diameter and its surface has an albedo 0.06,[5] while the Collaborative Asteroid Lightcurve Link assumes a standard albedo for a carbonaceous asteroid of 0.057 and calculates a diameter of 19.21 kilometers based on an absolute magnitude of 12.31.[6]


This minor planet was named by IAU's Minor Planet Names Committee from Greek mythology after the warrior Acamas (son of Eussorus), ally of Troy and leader of the Thracian contingent during the Trojan War. He was killed by Ajax.[1]

The name was suggested by Frederick Pilcher and published by the Minor Planet Center on 6 February 1993 (M.P.C. 21606).[1][8]


  1. ^ a b c d e f g h i "2594 Acamas (1978 TB)". Minor Planet Center. Retrieved 21 June 2018.
  2. ^ a b c d "JPL Small-Body Database Browser: 2594 Acamas (1978 TB)" (2018-02-25 last obs.). Jet Propulsion Laboratory. Retrieved 21 June 2018.
  3. ^ "List of Jupiter Trojans". Minor Planet Center. 1 June 2018. Retrieved 21 June 2018.
  4. ^ a b "Asteroid (2594) Acamas – Proper Elements". AstDyS-2, Asteroids – Dynamic Site. Retrieved 21 June 2018.
  5. ^ a b c d 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 21 June 2018. (online catalog)
  6. ^ a b c d e f g "LCDB Data for (2594) Acamas". Asteroid Lightcurve Database (LCDB). Retrieved 21 June 2018.
  7. ^ a b 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 21 June 2018.
  8. ^ "MPC/MPO/MPS Archive". Minor Planet Center. Retrieved 21 June 2018.

External links[edit]