433 Eros
433 Eros is the first Near-Earth asteroid (NEA) that was found. It was named after the Greek god of love, Eros (Greek Ἔρως). It is an S-type asteroid about 13 × 13 × 33 km in size, the second-biggest near-Earth asteroid (NEA) after 1036 Ganymed. It belongs to the Amors. It is the first asteroid that was known to cross inside the orbit of Mars. Eros is one of the few NEAs bigger than 10 km across. It is thought to be bigger than the asteroid that made the Chicxulub crater in the Yucatán and probably caused the extinction of the dinosaurs.[1]
 This picture of Eros shows the view looking from one end of the asteroid across the gouge on its underside and toward the opposite end. | |
| Discovery | |
|---|---|
| Discovered by | Carl Gustav Witt |
| Discovery date | August 13, 1898 |
| Designations | |
| 1898 DQ; 1956 PC | |
| Amor, Mars-crosser asteroid | |
| Orbital characteristics | |
| Epoch October 22, 2004 (JD 2453300.5) | |
| Aphelion | 266.762 Gm (1.783 AU) |
| Perihelion | 169.548 Gm (1.133 AU) |
| 218.155 Gm (1.458 AU) | |
| Eccentricity | 0.223 |
| 643.219 d (1.76 a) | |
Average orbital speed | 24.36 km/s |
| 320.215° | |
| Inclination | 10.829° |
| 304.401° | |
| 178.664° | |
| Physical characteristics | |
| Dimensions | 13×13×33 km |
| Mass | 7.2×1015 kg |
Mean density | 2.4 g/cm³ |
| 0.0059 m/s² | |
| 0.0103 km/s | |
| 0.2194 d (5 h 16 min) | |
| Albedo | 0.16 |
| Temperature | ~227 K |
Spectral type | S |
| +7.1 to +15 | |
| 11.16 | |
On January 31, 2012, Eros passed close to Earth at 0.1787 astronomical units (16.6 million miles). This is about 700 times farther from the Earth than the moon is. It had brightness of +8.1 visual magnitude.
During rare oppositions, every 81 years, such as in 1975 and 2056, Eros will be directly away from the sun, as seen from Earth. Then, Eros can reach a magnitude of +7.1, which is brighter than Neptune and brighter than any main belt asteroid except 4 Vesta (and sometimes 2 Pallas and 7 Iris). At opposition, the asteroid actually appears to stop in place when compared to stars in the sky. Unlike most objects in the solar system, it never appears to be retrograde (back-track across the sky).
Eros was visited by the NEAR Shoemaker probe, which orbited it, taking many pictures of its surface. On February 12, 2001, at the end of its mission, NEAR landed on the asteroid's surface using its maneuvering jets.
Objects in an orbit like Eros can exist for only a few hundred million years before the orbit is changed by the effects of gravity. Simulations suggest that Eros may evolve into an Earth-crosser within 2 million years (Michel et al., 1996).
The adjectival form which is not used a lot of the name Eros is Erotian.
Physical characteristics
Surface gravity depends on the distance from a spot on the surface to the center of a body's mass. The Erotian surface gravity changes a lot, since Eros is not a sphere but a stretched peanut-shaped (or potato- or shoe-shaped) object. The daytime temperature on Eros stays at about 100 °C and nighttime measurements at −150 °C. Eros's density is 2,400 kg/m3, about the same as the density of Earth's crust. Its day lasts 5.27 hours.
NEAR scientists have found that most of the bigger rocks scattered across Eros were blown from a single crater in a meteorite collision approximately 1 billion years ago. This impact may also be the reason why nearly half of the Erotian surface doesn't have small craters. It was first thought that the debris thrown up by the collision filled in the smaller craters (those less than half a kilometer across). A study of crater on the surface shows that the areas with the fewest craters are within 9 kilometers of the impact point. This includes the opposite side of the asteroid but still within 9 kilometers.
History
Eros was found on the same night (13 August 1898) by Gustav Witt in Berlin and Auguste Charlois at Nice.[2] Witt was taking a 2-hour exposure of beta Aquarius to get astrometric positions of asteroid 185 Eunike.[3]
In 1975, Eros became the first asteroid to be detected by radar.[4]
Eros was one of the first asteroids to be visited by a spacecraft, and the first to be orbited and soft-landed on. NASA spacecraft NEAR Shoemaker entered orbit around Eros in 2000, and came to rest on its surface in 2001.
References and Notes
- Thomas PC, Robinson MS (1970). "Seismic resurfacing by a single impact on the asteroid 433 Eros". Nature. 436 (7049): 366–9. PMID 16034412
- ↑ Dividing the mass of 433 Eros by its density gives a volume of 3000 km3, while the estimated 5 km radius of the (assumed spherical) Chicxulub Crater impactor yields a volume of only about 520 km3.
- ↑ Scholl, Hans and Lutz D. Schmadel, "Discovery Circumstances of the First Near-Earth Asteroid (433) Eros", Beiträge zur Astronomiegeschichte, vol. 5, p. 210-220 (2002)
- ↑ "Archived copy" (PDF). Archived from the original (PDF) on 2007-09-28. Retrieved 2008-01-13.
{{cite web}}: CS1 maint: archived copy as title (link) - ↑ http://www.iac.es/galeria/mrk/Eros_eng.html
Other websites
- NEAR Shoemaker spacecraft
- NEAR image of the day archive
- Movie: NEAR Shoemaker spacecraft landing
- The Eros Project (OrbDev's attempts at litigation over their property claim)
- Orbital simulation from JPL (Java)
- NEODys (saved output file) showing distance and magnitude Ephemerides for Eros during rare oppositions