5477 Holmes
Hungaria asteroid and binary system
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5477 Holmes, provisional designation 1989 UH2, is a Hungaria asteroid and binary system from the innermost regions of the asteroid belt, approximately 3 kilometers (2 miles) in diameter. It was discovered on 27 October 1989, by American astronomer Eleanor Helin at the Palomar Observatory in California.[1] The presumed E-type asteroid is likely spherical in shape and has a short rotation period of 2.99 hours.[3] It was named for American amateur astronomer Robert Holmes.[1] The discovery of its 1-kilometer-sized minor-planet moon was announced in November 2005.[5][6]
| Discovery[1] | |
|---|---|
| Discovered by | E. F. Helin |
| Discovery site | Palomar Obs. |
| Discovery date | 27 October 1989 |
| Designations | |
| (5477) Holmes | |
Named after | Robert Holmes[1] (American astronomer) |
| 1989 UH2 | |
| main-belt · (inner)[2] Hungaria[1][3][4] | |
| Orbital characteristics[2] | |
| Epoch 23 March 2018 (JD 2458200.5) | |
| Uncertainty parameter 0 | |
| Observation arc | 27.60 yr (10,082 d) |
| Aphelion | 2.0613 AU |
| Perihelion | 1.7732 AU |
| 1.9172 AU | |
| Eccentricity | 0.0751 |
| 2.65 yr (970 d) | |
| 295.23° | |
| 0° 22m 16.68s / day | |
| Inclination | 22.552° |
| 49.112° | |
| 290.30° | |
| Known satellites | 1 (D: 1.09 km P: 24.4 h)[3][5][6] |
| Physical characteristics | |
| 2.95±0.13 km (derived)[5] 3.147±0.137 km[7][8] 3.21 km (taken)[3] 3.215 km[9] | |
| 2.9932±0.0002 h[10][a] 2.9940±0.0002 h[11] 2.99401±0.00007 h[12] 2.99408±0.00007 h[13] 2.9943±0.0002 h[6] | |
| 0.2849[9] 0.310±0.038[7][8] | |
| E (assumed)[3] | |
| 13.99±0.03 (R)[12] 14.0[2] 14.26±0.54[14] 14.4[8][13] 14.445[3][9] | |
Orbit and classification
Holmes is a core member of the Hungaria family (003),[4] a large family of bright asteroids that forms the innermost dense concentration of asteroids in the Solar System, as the Mars-crosser and near-Earth populations are much more sparse. The family is part of the larger dynamical group with the same name.[1][3] It orbits the Sun in the innermost asteroid belt at a distance of 1.8–2.1 AU once every 2 years and 8 months (970 days; semi-major axis of 1.92 AU). Its orbit has an eccentricity of 0.08 and an inclination of 23° with respect to the ecliptic.[2] The body's observation arc begins with its official discovery observation at Palomar in October 1989.[1]
Physical characteristics
Holmes is an assumed E-type asteroid,[3] which agrees with the overall spectral type for members of the Hungaria family.[15]: 23
Rotation period
Since 2005, several rotational lightcurves of Holmes have been obtained from photometric observations by Brian Warner and Petr Pravec in collaboration with other astronomers.[6][10][11][12][13][a] Analysis of the best-rated lightcurve gave a well-defined rotation period of 2.9940 hours with a consolidated brightness amplitude between 0.10 and 0.12 magnitude, which indicates that the body has a nearly spherical shape (U=3).[3][11] The asteroid's short period is near that of a fast rotator.
Diameter and albedo
According to the survey carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer (WISE), Holmes measures 3.147 kilometers in diameter and its surface has an albedo of 0.31,[7][8] while the Collaborative Asteroid Lightcurve Link adopts Petr Pravec's revised WISE-data, that is, an albedo of 0.2849 and a diameter of 3.21 kilometers based on an absolute magnitude of 14.445.[3][9] Johnston's Archive derives a diameter of 2.95 and 3.15 kilometers for the primary only and for the combined system, respectively.[5]
Satellite
The photometric observations obtained by Brian Warner and collaborators during 2–12 November 2005,[13] revealed that Holmes is a synchronous binary asteroid with a minor-planet moon orbiting it every 24.4 hours at an estimated average distance of 6.7 km. The discovery was announced immediately on 15 November 2005.[6] The mutual occultation events indicated the presence of a satellite 37% the size of its primary, which translates into an estimated diameter of 1.09–1.19 kilometers depending on the underlying size estimate of the primary.[3][5]
Naming
This minor planet was named after American amateur astronomer Robert E. Holmes Jr (born 1956), who directs the Astronomical Research Observatory (H21) in Westfield, Illinois.[1] The official naming citation was suggested by Sergio Foglia and published by the Minor Planet Center on 18 February 2011 (M.P.C. 73983).[16]
Notes
- Lightcurve plot of 5477 Holmes, Palmer Divide Observatory, Brian D. Warner (2012). Rotation period 2.9932±0.0002 hours with a brightness amplitude of 0.10±0.01 mag. The second plot for the orbital period of the satellite gives a period of 24.37±0.01 hours. Quality code is 3. Summary figures at the LCDB.
