25143 Itokawa

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25143 Itokawa
Discovery
Discovered by LINEAR
Discovery date September 26, 1998
Designations
Alternative names 1998 SF36
Minor planet
category		 Apollo asteroid,
Mars-crosser asteroid
Epoch August 18, 2005 (JD 2453600.5)
Aphelion 253.520 Gm (1.695 AU)
Perihelion 142.568 Gm (0.953 AU)
Semi-major axis 198.044 Gm (1.324 AU)
Eccentricity 0.280
Orbital period 556.355 d (1.52 a)
Average orbital speed 25.37 km/s
Mean anomaly 294.502°
Inclination 1.622°
Longitude of ascending node 69.095°
Argument of perihelion 162.760°
Physical characteristics
Dimensions 535 × 294 × 209 m [1]
Mass (3.51±0.105)×1010 kg [1], (3.58±0.18)×1010 kg [2]
Mean density 1.9 ±0.13 g/cm³ [1], 1.95 ± 0.14 g/cm³ [2]
Equatorial surface gravity ~0.0001 m/s²
Escape velocity ~0.0002 km/s
Rotation period 0.5055 d (12.132 h) [3]
Albedo 0.53
Temperature ~206 K
Spectral type S
Absolute magnitude 19.2

25143 Itokawa (pronounced /ˌiːtoʊˈkɑːwə/, Japanese イトカワ, from 糸川) is an Apollo and Mars-crosser asteroid. It was the focus of detailed study by the Japanese space probe Hayabusa and may become the first asteroid sample-return target.

Contents

[edit] History

The asteroid was discovered in 1998 by the LINEAR project, and given the provisional designation 1998 SF36. In 2000, it was selected as the target of Japan's Hayabusa mission. Soon thereafter, it was officially named after Hideo Itokawa, a Japanese rocket scientist.

[edit] Description

Itokawa is an S-type asteroid. Radar imaging by Goldstone revealed an elongated irregular shape. [1]

The Hayabusa mission confirmed these findings and also suggested that Itokawa may be a contact binary formed by two or more smaller asteroids that have gravitated toward each other and stuck together. The Hayabusa images show a surprising lack of impact craters, and a very rough surface studded with boulders, these particular boulders were referred by the mission team, as being in a 'rubble'. [2] This would mean that Itokawa is not a monolith but rather a ‘rubble pile’ formed from fragments that have cohered over time.

[edit] Hayabusa mission

The Japanese probe Hayabusa arrived in the vicinity of Itokawa on September 12, 2005 and initially "parked" in an asteroid-sun line at 20 km, and later 7 km, from the asteroid. Hayabusa landed November 20 for thirty minutes, but failed to operate a device designed to collect soil samples. On November 25, a second landing and the sampling sequence was attempted. Hayabusa has since left the asteroid, and the sample capsule is planned to land at Woomera, South Australia in 2010; however, it is unclear if any samples were collected.

[edit] Named surface features

Names of major features were proposed by Hayabusa scientists and accepted by the Working Group for Planetary System Nomenclature of the International Astronomical Union. See the list of geological features on 25143 Itokawa.

Also, the Hayabusa science team is using working names for smaller surface features. [3] [4]

[edit] References

  1. ^ a b c Akira Fujiwara, et al., The Rubble-Pile Asteroid Itokawa as Observed by Hayabusa, Science, Vol. 312. no. 5778, pp. 1330 - 1334, June 2, 2006
  2. ^ a b Shunsuke Abe, et al., Mass and Local Topography Measurements of Itokawa by Hayabusa, Science, Vol. 312. no. 5778, pp. 1344 - 1347, June 2, 2006
  3. ^ M. Kaasalainen, et al., CCD photometry and model of MUSES-C target (25143) 1998 SF36, Astronomy and Astrophysics, v.405, p.L29-L32 (2003)

[edit] External links

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