Asteroid 25143 Itokawa observed by Hayabusa. Image provided by JAXA.
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Discovery
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| Discovered by | LINEAR |
| Discovery date | September 26, 1998 |
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Designations
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| Alternate name | 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° |
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Physical characteristics
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| 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 (H) | 19.2 |
25143 Itokawa (pronounced /ˌiːtoʊˈkɑːwə/, Japanese イトカワ, from 糸川) is an Apollo and Mars-crosser asteroid. It was the first asteroid to be the target of a sample return mission, the Japanese space probe Hayabusa.
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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.
Description
Itokawa is an S-type asteroid. Radar imaging by Goldstone revealed an elongated irregular shape.[4]
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, but a very rough surface studded with boulders. These particular boulders were referred by the mission team as being in a 'rubble'.[5] This would mean that Itokawa is not a monolith but rather a ‘rubble pile’ formed from fragments that have cohered over time.
Shape from Goldstone and Arecibo Radars (Itokawa)
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.
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.
Also, the Hayabusa science team is using working names for smaller surface features.[6][7]
Further reading
- Durech, J. (September 2008). "New photometric observations of asteroids (1862) Apollo and (25143) Itokawa – an analysis of YORP effect". Astronomy and Astrophysics 488 (1): 345–350. doi:. http://www.rni.helsinki.fi/~mjk/YorpApoIto.pdf.
References
- ^ 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
- ^ 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
- ^ M. Kaasalainen, et al., CCD photometry and model of MUSES-C target (25143) 1998 SF36, Astronomy and Astrophysics, v.405, p.L29-L32 (2003)
- ^ "Radar Observations of Asteroid 25143 Itokawa (1998 SF36)". http://echo.jpl.nasa.gov/~ostro/itokawa.html. Retrieved 2008-08-11. mirror
- ^ "Hayabusa: Itokawa Beckons as Japan's Spacecraft Searches for Places to Touch Down". http://www.planetary.org/news/2005/0916_Hayabusa_Itokawa_Beckons_as_Japans.html. Retrieved 2008-08-11. mirror
- ^ "Itowaka Geological Map". http://www.isas.jaxa.jp/e/snews/2006/image/0602/b/08.jpg. Retrieved 2008-08-11. mirror
- ^ "Local site names on Itowaka". http://www.isas.jaxa.jp/e/snews/2006/image/0602/b/09.jpg. Retrieved 2008-08-11. mirror
External links
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Wikimedia Commons has media related to: 25143 Itokawa |
- Close-up images of Itokawa, a rubble pile asteroid
- Hayabusa mission Video March 2007
- Gazetteer of Planetary Nomenclature
- MIT's LINEAR asteroid named for Japan's 'Dr. Rocket' (MIT press release)
- Latest news and images from Hayabusa (JAXA Hayabusa official page)
- Hayabusa's Scientific and Engineering Achievements during Proximity Operations around Itokawa (JAXA press release)
- Earth impact probability of the Asteroid (25143) Itokawa to be sampled by the spacecraft Hayabusa (paper abstract)
- Astronomy Picture Of The Day: Approaching Asteroid Itokawa, A Robot's Shadow on Asteroid Itokawa, The Missing Craters of Asteroid Itokawa, Smooth Sections on Asteroid Itokawa
- Special issue: Hayabusa at Itokawa, Science, Vol. 312, no. 5778, June 2, 2006
- Initial Scientific Results of Hayabusa’s Investigation on Itokawa ~Summary of the Special Issue of “Science”Magazine~ (ISAS/JAXA press release)
- Animated model of Itokawa rotating (in anaglyph form for use with red-blue glasses)
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