1620 Geographos
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| Discovery A | |
|---|---|
| Discoverer | Albert Wilson, Rudolph Minkowski |
| Discovery date | September 14, 1951 |
| Alternate designations B |
1951 RA |
| Category | Apollo, Mars-crosser |
| Orbital elements C | |
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|
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| Eccentricity (e) | 0.335 |
| Semi-major axis (a) | 186.314 Gm (1.245 AU) |
| Perihelion (q) | 123.817 Gm (0.828 AU) |
| Aphelion (Q) | 248.810 Gm (1.663 AU) |
| Orbital period (P) | 507.665 d (1.39 a) |
| Mean orbital speed | 25.92 km/s |
| Inclination (i) | 13.341° |
| Longitude of the ascending node (Ω) |
337.293° |
| Argument of perihelion (ω) |
276.793° |
| Mean anomaly (M) | 147.839° |
| Physical characteristics D | |
| Dimensions | 5.1×1.8 km |
| Mass | ~2.6×1013 kg |
| Density | 2.0? g/cm³ |
| Surface gravity | ~0.0008 m/s² |
| Escape velocity | ~0.0015 km/s |
| Rotation period | 0.217 d (5.2 h) |
| Spectral class | S |
| Absolute magnitude | 15.60 |
| Albedo (geometric) | 0.10 |
| Mean surface temperature |
~249 K |
The asteroid 1620 Geographos was discovered on September 14, 1951 at the Palomar Observatory by Albert Wilson and Rudolph Minkowski. It was originally given the provisional designation 1951 RA. Its name means geographer and was chosen to honour the National Geographic Society.
Geographos is Mars-crosser asteroid and a near-Earth object belonging to the Apollos. In 1994, during the asteroid's closest approach to Earth in two centuries at 5.0 Gm-which will not be bettered until 2586- a radar study of it was conducted by the Deep Space Network at Goldstone, California. The resultant images show Geographos to be the most elongated object in the solar system; it measures 5.1×1.8 km.
Geographos is an S-type asteroid, meaning that it is highly reflective and composed of nickel-iron mixed with iron- and magnesium-silicates.
Geographos was to be explored by the U.S.'s Clementine mission; however, a malfunctioning thruster ended the mission before it could approach the asteroid.
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