颖神星
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5个分类: 正在翻譯的條目 | Main Belt asteroids | Asteroids named from Greek mythology | S-type asteroids | 来自中文维基百科
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本條目仍然有文字尚未被翻譯成中文，條目是根據http://en.wikipedia.org/wiki/9_Metis進行翻譯。 歡迎您積極參與翻譯與修訂，目前翻譯的進度為35%。 |
| Image:9AS2.jpg Convex hull model of 9 Metis |
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| 發現 | |
|---|---|
| 發現者： | A. Graham |
| 發現日期： | April 25, 1848 |
| 其他名稱： | 1974 QU2 |
| 小行星分類： | Main belt |
| 軌道資料 | |
| 曆元 July 14, 2004 (JD 2453200.5) | |
| 遠日點距離： | 400.548 Gm (2.678 AU) |
| 近日點距離： | 313.556 Gm (2.096 AU) |
| 軌道長半徑： | 357.052 Gm (2.387 AU) |
| 軌道離心率： | 0.122 |
| 軌道周期： | 1346.815 d (3.69 a) |
| 平均公轉速度： | 19.21 km/s |
| 平均近點角： | 274.183° |
| 軌道傾角： | 5.576° |
| 昇交點赤經： | 68.982° |
| 近日點輻角： | 5.489° |
| 物理特徵 | |
| 大小： | 235×195×140 km[1][2] |
| 質量： | ~9×1018 kg |
| 平均密度： | ~2.7 g/cm³[3] |
| 赤道表面重力： | ~0.070 m/s² |
| 宇宙速度： | ~0.11 km/s |
| 自轉週期： | 0.2116 d (5.078 h)[4] |
| 反照率： | 0.243[6] |
| 溫度： | ~173 K max: 282 K (+9° C)[7] |
| 光譜類型： | S-type[5] |
| 絕對星等： | 6.28 |
穎神星（亦稱9號小行星）是小行星帶較大的小行星之一，由矽酸鹽、鎳和鐵組成，並且有可能是古代一顆巨大的小行星撞擊后的核心殘留物。
目录 |
[编辑] 發現和命名
穎神星是由Andrew Graham於1848年4月25日發現，是他發現的唯一一顆小行星。它也是唯一一顆在愛爾蘭觀測發現的小行星。名稱的由來是神話中的泰坦女神和海洋女神墨提斯，是太西絲和海洋之神的女兒。西蒂斯這個名稱也曾經被提議，但後來被否決了（名稱後來被用在17海女星）。
[编辑] 特性
基於資料不明確，穎神星自轉方向至今仍不明。
Lightcurve analysis indicates that Metis' pole points towards either ecliptic coordinates (β, λ) = (23°, 181°) or (9°, 359°) with a 10° uncertainty.[1] The equivalent equatorial coordinates are (α, δ) = (12.7 h, 21°) or (23.7 h, 8°). This gives an axial tilt of 72° or 76°, respectively.[來源請求]
Hubble space telescope images[2][8] and lightcurve analyses[1] are in agreement that Metis has an irregular elongated shape with one pointed and one broad end.[1][8] Radar observations suggest the presence of a significant flat area,[9] in agreement with the shape model from lightcurves.
The surface composition has been estimated as 30-40% metal-bearing olivine and 60-70% Ni-Fe metal.[10]
Light curve data on Metis led to an assumption that it could have a satellite. However, subsequent observations failed to confirm this.[11][12] Later searches with the Hubble Space Telescope in 1993 found no satellites.[8]
[编辑] Family relationships
Metis was once considered to be a member of an asteroid family known as the Metis family,[13] but more recent searches for prominent families did not recognize any such group, nor is a clump evident in the vicinity of Metis by visual inspection of proper orbital element diagrams.
However, a spectroscopic analysis found strong spectral similarities between Metis and 113 Amalthea, and it is suggested that these asteroids may be remnants of a very old (at least ~1 Ga) dynamical family whose smaller members have been pulverised by collisions or perturbed away from the vicinity. The putative parent body is estimated to have been 300 to 600 km in diameter (Vesta-sized) and differentiated. Metis would be the relatively intact core remnant, and Amalthea a fragment of the mantle.[10] Coincidentally, both Metis and Amalthea have namesakes among Jupiter's inner moons.
[编辑] Occultations
Metis has been observed to occult stars no less than 5 times.[14]
[编辑] 參見
- ^ 1.0 1.1 1.2 1.3 J. Torppa et al., Shapes and rotational properties of thirty asteroids from photometric data, Icarus Vol. 164, p. 346 (2003).
- ^ 2.0 2.1 A. D. Storrs et al., A closer look at main belt asteroids 1: WF/PC images, Icarus Vol. 173, p. 409 (2005).
- ↑ G. A. Krasinsky et al., Hidden Mass in the Asteroid Belt, Icarus, Vol. 158, p. 98 (2002).
- ↑ PDS lightcurve data
- ↑ asteroid lightcurve data file (March 2001)
- ↑ MSX Infrared minor planet survey (at PDS)
- ↑ L. F. Lim et al., Thermal infrared (8–13 µm) spectra of 29 asteroids: the Cornell Mid-Infrared Asteroid Spectroscopy (MIDAS) Survey, Icarus Vol. 173, p. 385 (2005).
- ^ 8.0 8.1 8.2 Hubble Space Telescope observations
- ↑ D. L. Mitchell et al., Radar Observations of Asteroids 7 Iris, 9 Metis, 12 Victoria, 216 Kleopatra, and 654 Zelinda, Icarus Vol. 118, p. 105 (1995).
- ^ 10.0 10.1
- ↑ research at IMCCE (in French)
- ↑ "other" reports of asteroid companions
- ↑ J. G. Williams, Asteroid Families - An Initial Search, Icarus Vol. 96, p. 251 (1992).
- ↑ W. M. Kissling et al., The diameter of (9) Metis from the Occultation of SAO 190531, Proceedings of the Astronomical Society of Australia Vol 9, p. 150 (1991).
[编辑] 外部鏈接
- shape model deduced from lightcurve
- "Notice of discovery of Metis", MNRAS 8 (1848) 146
- Irish Astronomical History: Markree Castle Observatory and The Discovery of the Asteroid Metis
- Yeomans·Donald K. - Horizons system NASA JPL - 於2007-03-20访问。 — Horizons can be used to obtain a current ephemeris.
| 小行星 |
| 水内小行星 (祝融星) | 小行星带 | 近地小行星 (近地天体) | 特洛伊小行星 | |
| 半人马小行星 | 外海王星天體 | 達摩克小行星 | 彗星 | 柯伊伯带 | 奥尔特云 |
| 欲其他天体或区域，请参见：小行星衛星、太阳系 |
| 完整列表请见：小行星列表 |
| 前一小行星： (8)花神星 |
小行星列表 | 後一小行星： (10)健神星 |
