69230 Hermes
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| Discovery | |
|---|---|
| Discovered by: | Karl Wilhelm Reinmuth |
| Discovery date: | October 28, 1937 |
| Alternative names: | 1937 UB |
| Minor planet category: | Apollo, Mars-crosser, Venus-crosser |
| Orbital characteristics | |
| Epoch November 26, 2005 (JD 2453700.5) | |
| Aphelion distance: | 402.084 Gm (2.688 AU) |
| Perihelion distance: | 93.115 Gm (0.622 AU) |
| Semi-major axis: | 247.599 Gm (1.655 AU) |
| Eccentricity: | 0.624 |
| Orbital period: | 777.739 d (2.13 a) |
| Avg. orbital speed: | 20.70 km/s |
| Mean anomaly: | 325.865° |
| Inclination: | 6.068° |
| Longitude of ascending node: | 34.511° |
| Argument of perihelion: | 92.397° |
| Physical characteristics | |
| Dimensions: | 0.4 km |
| Mass: | 6.7×1010 kg |
| Mean density: | 2.0? g/cm³ |
| Equatorial surface gravity: | 0.0001? m/s² |
| Escape velocity: | 0.0002? km/s |
| Rotation period: | 0.57883±0.00025 d (13.892±0.006 h) [1] |
| Albedo: | 0.1? |
| Temperature: | ~216 K |
| Spectral type: | S |
| Absolute magnitude: | 17.5 |
69230 Hermes is an Apollo, Mars- and Venus-crosser asteroid that passed within 0.005 AU of the Earth (approximately 1.9 times the distance of the Moon) on October 30, 1937. It is named after the Greek god Hermes.
At the time, this was the closest known approach of an asteroid to the Earth. Not until 1989 was a closer approach (by 4581 Asclepius) observed. At closest approach, Hermes was moving 5° per hour across the sky and reached 8th magnitude.
It was discovered by Karl Reinmuth in images taken on October 28, 1937. Only five days of observations could be made before Hermes became too faint to be seen in the telescopes of the day. This was not enough to calculate an orbit, and Hermes was "lost". It thus did not receive a number, but Reinmuth nevertheless named it after the Greek god Hermes. It was the only unnumbered but named asteroid, having only the provisional designation 1937 UB.
On October 15, 2003, Brian A. Skiff of the LONEOS project made an asteroid observation that, when the orbit was calculated backwards in time (by Timothy B. Spahr, Steven Chesley and Paul Chodas), turned out to be a rediscovery of Hermes. The orbit is now well known, and Hermes has been assigned sequential number 69230. In retrospect it turned out that Hermes came even closer to the Earth in 1942 than in 1937, within 1.7 Moon distances without being observed.
Hermes is an S-type asteroid, a classification first reported by Andy Rivkin and Richard Binzel. Radar observations led by Jean-Luc Margot at Arecibo Observatory and Goldstone in October and November of 2003 showed Hermes to be a binary asteroid. The primary and secondary components have nearly identical radii of about 300 m, and their orbital separation is only 1200 m.
[edit] External links
| Minor planets | ||
|---|---|---|
| Previous minor planet | 69230 Hermes | Next minor planet |
| List of asteroids | ||
Vulcanoids · Near-Earth asteroids · Main belt · Jupiter Trojans · Centaurs · Damocloids · Comets · Trans-Neptunians (Kuiper belt • Scattered disc • Oort cloud)
For other objects and regions, see Asteroid groups and families, Binary asteroids, Asteroid moons and the Solar System.
For a complete listing, see List of asteroids. See also Pronunciation of asteroid names and Meanings of asteroid names.
