5261 Eureka
|
|
| Discovery A (http://cfa-www.harvard.edu/iau/lists/NumberedMPs.html) | |
|---|---|
| Discoverer | David H. Levy |
| Discovery date | June 20, 1990 |
| Alternate designations | 1990 MB B (http://cfa-www.harvard.edu/iau/MPDes.html) |
| Category | Mars-crosser asteroid |
| Orbital elements C (http://asteroid.lowell.edu/) Epoch July 14, 2004 (JD 2453200.5) | |
| Eccentricity (e) | 0.065 |
| Semi-major axis (a) | 227.908 Gm (1.523 AU) |
| Perihelion (q) | 213.132 Gm (1.425 AU) |
| Aphelion (Q) | 242.684 Gm (1.622 AU) |
| Orbital period (P) | 686.829 d (1.88 a) |
| Mean orbital speed | 24.13 km/s |
| Inclination (i) | 20.280° |
| Longitude of the ascending node (Ω) | 245.108° |
| Argument of perihelion (ω) | 95.361° |
| Mean anomaly (M) | 104.086° |
| Physical characteristics | |
| Dimensions | ? km |
| Mass | ? kg |
| Density | ? g/cm³ |
| Surface gravity | ? m/s² |
| Escape velocity | ? km/s |
| Rotation period | ? d |
| Spectral class | ? |
| Absolute magnitude | 16.1 |
| Albedo | ? |
| Mean surface temperature | ~225 K |
5261 Eureka was discovered at Mt Palomar on June 20, 1990 and turned out to be the first known Mars Trojan asteroid. It trails Mars (at the L5 point) at a distance varying by only 0.3 AU during each revolution (with a secular trend superimposed, changing the distance from 1.5-1.8 AU around 1850 to 1.3-1.6 AU around 2400). Minimum distances from the Earth, Venus and Jupiter are 0.5, 0.8 and 3.5 AU, respectively.
Long-term numerical integration shows that the orbit is stable. Kimmo A. Innanen and Seppo Mikkola note that "contrary to intuition, there is clear empirical evidence for the stability of motion around the L4 and L5 points of all the terrestrial planets over a timeframe of several million years".
Since then, other Mars Trojans have been identified; namely 1999 UJ7 at the L4 point and 1998 VF31, 2001 DH47, 2001 FG24, and 2001 FR127 at the L5 point. The co-orbitals 1998 QH56 and 1998 SD4 are not destined to remain as Trojans —they'll be perturbed away by Mars within the next 500,000 years or so.
References
- IAUC 5045 (http://cfa-www.harvard.edu/iauc/05000/05045.html#Item1)
- IAUC 5047 (http://cfa-www.harvard.edu/iauc/05000/05047.html#Item3)
- IAUC 5067 (http://cfa-www.harvard.edu/iauc/05000/05067.html#Item1)
- IAUC 5075 (http://cfa-www.harvard.edu/iauc/05000/05075.html#Item2)
| The minor planets |
| Vulcanoids | Main belt | Groups and families | Near-Earth objects | Jupiter Trojans |
| Centaurs | Trans-Neptunians | Damocloids | Comets | Kuiper belt | Oort cloud |
| (For other objects and regions, see: Binary asteroids, Asteroid moons and the Solar system) |
| (For a complete listing, see: List of asteroids. For pronunciation, see: Pronunciation of asteroid names.) |