双卫一

双卫一
	攝於2022年9月
发现
發現者	Petr Pravec（英语：Petr Pravec） et al.
發現日期	2003年11月20日
編號
其它名稱	S/2003 (65803) 1
軌道參數
	曆元 7.5 2011年1月 (儒略日 2455873.0)
半長軸	1.19±0.03 km (撞击前)
離心率	≤ 0.03
軌道週期	11.9216262±0.0000027 hr (11h 55m 18s; 撞击前); 11h 23m ± 2m (撞击后)
平均軌道速度	0.174 m/s (撞击前)
平近點角	89.2°±1.8°
軌道傾角	168.6°±1.8° 相對於黄道
隸屬天体	雙生星
物理特徵
大小	208 米 × 160 米 × 133 米
質量	~5×109 kg (推測)
自轉週期	潮汐鎖定?
反照率	0.15±0.04
光譜類型	S-型小行星
絕對星等(H)	21.3±0.2

双卫一是近地天体雙生星的一颗衛星。它的直径为170米（560英尺），與罗马斗兽场相當，重约480万吨。它与雙生星中心相距约1190米^[7]。2003年，有人在翁德热约夫天文台發現了双卫一。2020年6月，國際天文聯會將這顆小行星衛星命名為雙衛一^[8]。2022年9月，美国国家航空航天局在開展雙小行星改道測試時將雙衛一列為撞擊目標，並故意讓一個航天器撞向双卫一，目的是改變双卫一的軌跡^[9]。

備註

^ Astronomers involved in the discovery of Dimorphos include Petr Pravec（英语：Petr Pravec）, L.A.M. Benner, M.C. Nolan, P. Kusnirak, D. Pray, J.D. Giorgini, R.F. Jurgens, 史蒂文·J·奥斯特罗, J.-L. Margot, C. Magri, A. Grauer, and S. Larson. The discovery used lightcurve and radar observations from the 喷气推进实验室, Pasadena, 加利福尼亚州; 阿雷西博天文台, Arecibo, 波多黎各; and 翁德热约夫天文台, Ondřejov, 捷克. ^[1]
^ Orbital parameters are those after the impact of DART, which changed the 轨道周期 by 32 minutes. Other possibly changed parameters remain to be reevaluated.^[3]
^ Scheirich and Pravec (2022) give the Dimorphos's orbit pole orientation in terms of 黃道坐標系, where $λ$ is 黃道坐標系 and $β$ is 黃道坐標系.^[4]^{（p. 4）} $β$ is the angular offset from the 黄道, whereas 軌道傾角 $i$ with respect to the ecliptic is the angular offset of the 黃極 from the 黃極, at $β$ = +90° ; $i$ with respect to the ecliptic would be the 角 of $β$ .^[5] Therefore, given $β$ = –78.6° , $i$ = 90° – (–78.6°) = 168.6° from the ecliptic.

参考文献

^ ^1.0 ^1.1 ^1.2 (65803) Didymos. www.johnstonsarchive.net. [2021-11-11]. （原始内容存档于2020-10-23）.
^ ^2.0 ^2.1 Naidu, Shantanu P.; Chesley, Steven R.; Farnocchia, Davide; Moskovitz, Nick; Pravec, Petr; Scheirich, Petr; Thomas, Cristina; Rivkin, Andrew S. Anticipating the DART impact: Orbit estimation of Dimorphos using a simplified model. The Planetary Science Journal. October 2022, 3 (10): 234. Bibcode:2022PSJ.....3..234N. S2CID 252815897. arXiv:2210.05101 . doi:10.3847/PSJ/ac91c0.
^ ^3.0 ^3.1 Dunbar, Brian. NASA Confirms DART Mission Impact Changed Asteroid's Motion in Space. NASA. 11 October 2022 [2022-10-11]. （原始内容存档于2023-03-07）（英语）.
^ Scheirich, P.; Pravec, P. Preimpact Mutual Orbit of the DART Target Binary Asteroid (65803) Didymos Derived from Observations of Mutual Events in 2003–2021. The Planetary Science Journal. July 2022, 3 (7): 12 [2023-01-21]. Bibcode:2022PSJ.....3..163S. S2CID 250650906. doi:10.3847/PSJ/ac7233. 163. （原始内容存档于2022-07-19）.
^ Coordinate transformations. Astronomy and Astrophysics. European Southern Observatory. January 1998 [17 June 2022]. （原始内容存档于17 June 2021）.
^ ^6.0 ^6.1 Nakano, Ryota; Hirabayashi, Masatoshi; Brozovic, M.; Nolan, M. C.; Ostro, S. J.; Margot, J. L.; et al. NASA's Double Asteroid Redirection Test (DART): Mutual Orbital Period Change Due to Reshaping in the Near-Earth Binary Asteroid System (65803) Didymos. The Planetary Science Journal. July 2022, 3 (7): 16 [2023-01-21]. Bibcode:2022PSJ.....3..148N. S2CID 250327233. doi:10.3847/PSJ/ac7566. 148. （原始内容存档于2022-09-27）.
^ 觀網財經. 人类首次行星防御演习，成功了. [2023-01-21]. （原始内容存档于2023-03-08）.
^ Temming, Maria. An asteroid's moon got a name so NASA can bump it off its course. Science News. 29 June 2020 [1 July 2020]. （原始内容存档于2021-09-12）.
^ Rincon, Paul. NASA DART asteroid spacecraft: Mission to smash into Dimorphos space rock launches. BBC News. 2021-11-24 [2021-11-25]. （原始内容存档于2022-01-01）（英国英语）.

[2] Astronomers involved in the discovery of Dimorphos include Petr Pravec（英语：Petr Pravec）, L.A.M. Benner, M.C. Nolan, P. Kusnirak, D. Pray, J.D. Giorgini, R.F. Jurgens, 史蒂文·J·奥斯特罗, J.-L. Margot, C. Magri, A. Grauer, and S. Larson. The discovery used lightcurve and radar observations from the 喷气推进实验室, Pasadena, 加利福尼亚州; 阿雷西博天文台, Arecibo, 波多黎各; and 翁德热约夫天文台, Ondřejov, 捷克. ^[1]

[5] Orbital parameters are those after the impact of DART, which changed the 轨道周期 by 32 minutes. Other possibly changed parameters remain to be reevaluated.^[3]

[pole-8] Scheirich and Pravec (2022) give the Dimorphos's orbit pole orientation in terms of 黃道坐標系, where $λ$ is 黃道坐標系 and $β$ is 黃道坐標系.^[4]^{（p. 4）} $β$ is the angular offset from the 黄道, whereas 軌道傾角 $i$ with respect to the ecliptic is the angular offset of the 黃極 from the 黃極, at $β$ = +90° ; $i$ with respect to the ecliptic would be the 角 of $β$ .^[5] Therefore, given $β$ = –78.6° , $i$ = 90° – (–78.6°) = 168.6° from the ecliptic.

[johnston-1] 1.0 ^1.1 ^1.2 (65803) Didymos. www.johnstonsarchive.net. [2021-11-11]. （原始内容存档于2020-10-23）.

[Naidu2022-3] 2.0 ^2.1 Naidu, Shantanu P.; Chesley, Steven R.; Farnocchia, Davide; Moskovitz, Nick; Pravec, Petr; Scheirich, Petr; Thomas, Cristina; Rivkin, Andrew S. Anticipating the DART impact: Orbit estimation of Dimorphos using a simplified model. The Planetary Science Journal. October 2022, 3 (10): 234. Bibcode:2022PSJ.....3..234N. S2CID 252815897. arXiv:2210.05101 . doi:10.3847/PSJ/ac91c0.

[DartPressUpdateNASA-4] 3.0 ^3.1 Dunbar, Brian. NASA Confirms DART Mission Impact Changed Asteroid's Motion in Space. NASA. 11 October 2022 [2022-10-11]. （原始内容存档于2023-03-07）（英语）.

[Scheirich2022-6] Scheirich, P.; Pravec, P. Preimpact Mutual Orbit of the DART Target Binary Asteroid (65803) Didymos Derived from Observations of Mutual Events in 2003–2021. The Planetary Science Journal. July 2022, 3 (7): 12 [2023-01-21]. Bibcode:2022PSJ.....3..163S. S2CID 250650906. doi:10.3847/PSJ/ac7233. 163. （原始内容存档于2022-07-19）.

[coordstransform-7] Coordinate transformations. Astronomy and Astrophysics. European Southern Observatory. January 1998 [17 June 2022]. （原始内容存档于17 June 2021）.

[Nakano2022-9] 6.0 ^6.1 Nakano, Ryota; Hirabayashi, Masatoshi; Brozovic, M.; Nolan, M. C.; Ostro, S. J.; Margot, J. L.; et al. NASA's Double Asteroid Redirection Test (DART): Mutual Orbital Period Change Due to Reshaping in the Near-Earth Binary Asteroid System (65803) Didymos. The Planetary Science Journal. July 2022, 3 (7): 16 [2023-01-21]. Bibcode:2022PSJ.....3..148N. S2CID 250327233. doi:10.3847/PSJ/ac7566. 148. （原始内容存档于2022-09-27）.

[10] 觀網財經. 人类首次行星防御演习，成功了. [2023-01-21]. （原始内容存档于2023-03-08）.

[Temming-2020-06-29-11] Temming, Maria. An asteroid's moon got a name so NASA can bump it off its course. Science News. 29 June 2020 [1 July 2020]. （原始内容存档于2021-09-12）.

[Rincon-2021-11-24-12] Rincon, Paul. NASA DART asteroid spacecraft: Mission to smash into Dimorphos space rock launches. BBC News. 2021-11-24 [2021-11-25]. （原始内容存档于2022-01-01）（英国英语）.

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