G 240-72

**G 240-72**
觀測資料; 曆元 J2000
星座	天龍座
星官
赤經	17h 48m 08.17s
赤緯	+70° 52′ 35.3″
視星等（V）	14.15
特性
光谱分类	DQP9.0
视星等 (B)	14.55
视星等 (V)	14.15
视星等 (R)	13.5
视星等 (I)	13.1
视星等 (J)	12.709 ± 0.021
视星等 (H)	12.528 ± 0.023
视星等 (K)	12.507 ± 0.023
天体测定
自行 (μ)	赤经：-1261 mas/yr ; 赤纬：1112 mas/yr
视差 (π)	160.9952 ± 0.0119 mas
距离	20.259 ± 0.001 ly ; (6.2114 ± 0.0005 pc)
绝对星等 (MV)	15.23
詳細資料
質量	0.81 ± 0.01 M☉
半徑	0.00984 R☉
表面重力 (log g)	8.36 ± 0.02
亮度	0.000085 L☉
溫度	5590 ± 90 K
自轉	>100 years
年齡	5.69 Gyr
其他命名
	WD 1748+708, LHS 455, LP 44-113, NLTT 45565, GJ 1221, EGGR 372, 2MASS J17480817+7052353
參考資料庫
SIMBAD	资料
	G 240-72 G 240-72 在天龍座的位置;

G 240-72 (或 WD 1748+708或 LHS 455或 GJ 1221) 是一顆位於天龍座附近的白矮星，光譜等級為 DQP9.0^[2]。

距離

G 240-72 是距離第七近的白矮星（僅次於天狼星B、南河三B、范馬南星、GJ 440、波江座40B和施泰因2051B）。

特性

G 240-72質量為0.81個太陽質量^[2]。

這顆白矮星的溫度相對較低，為5590K^[2]。由於其溫度與太陽相似，因此外觀呈白色。它有純氦大氣，自轉非常緩慢，週期可能超過100年。^[7]

參考

^ ^1.00 ^1.01 ^1.02 ^1.03 ^1.04 ^1.05 ^1.06 ^1.07 ^1.08 ^1.09 ^1.10 ^1.11 ^1.12 ^1.13 GJ 1221 -- White Dwarf. Centre de Données astronomiques de Strasbourg. [2011-10-23]. （原始内容存档于2023-03-22）.
^ ^2.00 ^2.01 ^2.02 ^2.03 ^2.04 ^2.05 ^2.06 ^2.07 ^2.08 ^2.09 ^2.10 ^2.11 Holberg, J. B.; Sion; Oswalt; McCook; Foran; Subasavage. A New Look at the Local White Dwarf Population. The Astronomical Journal. 2008, 135 (4): 1225–1238 [2023-03-22]. Bibcode:2008AJ....135.1225H. S2CID 122855486. doi:10.1088/0004-6256/135/4/1225. （原始内容存档于2023-04-20）.
^ ^3.0 ^3.1 ^3.2 ^3.3 Sion, Edward M.; Holberg; Oswalt; McCook; Wasatonic. The White Dwarfs within 20 Parsecs of the Sun: Kinematics and Statistics. The Astronomical Journal. 2009, 138 (6): 1681–1689. Bibcode:2009AJ....138.1681S. S2CID 119284418. arXiv:0910.1288  . doi:10.1088/0004-6256/138/6/1681.
^ Brown, A. G. A.; et al. Gaia Early Data Release 3: Summary of the contents and survey properties. Astronomy & Astrophysics. 2021, 649: A1. Bibcode:2021A&A...649A...1G. S2CID 227254300. arXiv:2012.01533  . doi:10.1051/0004-6361/202039657  . 已忽略未知参数|collaboration= (帮助) (勘误: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
^ ^5.0 ^5.1 Van Altena W. F.; Lee J. T.; Hoffleit E. D. GCTP 2835.01. The General Catalogue of Trigonometric Stellar Parallaxes Fourth. 1995 [2023-03-22]. （原始内容存档于2022-05-23）.
^ Giammichele, N.; Bergeron, P.; Dufour, P., Know Your Neighborhood: A Detailed Model Atmosphere Analysis of Nearby White Dwarfs, The Astrophysical Journal Supplement, April 2012, 199 (2): 29, Bibcode:2012ApJS..199...29G, S2CID 118304737, arXiv:1202.5581  , doi:10.1088/0067-0049/199/2/29.
^ ^7.0 ^7.1 MEASURING THE ROTATIONAL PERIODS OF ISOLATED MAGNETIC WHITE DWARFS. [2023-03-22]. （原始内容存档于2023-03-22）.

註釋

^ From apparent magnitude and parallax.
^ From surface gravity and mass.
^ Cooling age, i. e. age as degenerate star (not counting duration of previous existence as main sequence star and as giant star)

外部連結

The 100 Nearest Star Systems (RECONS)

[Simbad-1] 1.00 ^1.01 ^1.02 ^1.03 ^1.04 ^1.05 ^1.06 ^1.07 ^1.08 ^1.09 ^1.10 ^1.11 ^1.12 ^1.13 GJ 1221 -- White Dwarf. Centre de Données astronomiques de Strasbourg. [2011-10-23]. （原始内容存档于2023-03-22）.

[Holberg2008-2] 2.00 ^2.01 ^2.02 ^2.03 ^2.04 ^2.05 ^2.06 ^2.07 ^2.08 ^2.09 ^2.10 ^2.11 Holberg, J. B.; Sion; Oswalt; McCook; Foran; Subasavage. A New Look at the Local White Dwarf Population. The Astronomical Journal. 2008, 135 (4): 1225–1238 [2023-03-22]. Bibcode:2008AJ....135.1225H. S2CID 122855486. doi:10.1088/0004-6256/135/4/1225. （原始内容存档于2023-04-20）.

[Sion2009-3] 3.0 ^3.1 ^3.2 ^3.3 Sion, Edward M.; Holberg; Oswalt; McCook; Wasatonic. The White Dwarfs within 20 Parsecs of the Sun: Kinematics and Statistics. The Astronomical Journal. 2009, 138 (6): 1681–1689. Bibcode:2009AJ....138.1681S. S2CID 119284418. arXiv:0910.1288  . doi:10.1088/0004-6256/138/6/1681.

[GaiaEDR3-4] Brown, A. G. A.; et al. Gaia Early Data Release 3: Summary of the contents and survey properties. Astronomy & Astrophysics. 2021, 649: A1. Bibcode:2021A&A...649A...1G. S2CID 227254300. arXiv:2012.01533  . doi:10.1051/0004-6361/202039657  . 已忽略未知参数|collaboration= (帮助) (勘误: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.

[van_Altena1995-5] 5.0 ^5.1 Van Altena W. F.; Lee J. T.; Hoffleit E. D. GCTP 2835.01. The General Catalogue of Trigonometric Stellar Parallaxes Fourth. 1995 [2023-03-22]. （原始内容存档于2022-05-23）.

[ApJS199_2_29-8] Giammichele, N.; Bergeron, P.; Dufour, P., Know Your Neighborhood: A Detailed Model Atmosphere Analysis of Nearby White Dwarfs, The Astrophysical Journal Supplement, April 2012, 199 (2): 29, Bibcode:2012ApJS..199...29G, S2CID 118304737, arXiv:1202.5581  , doi:10.1088/0067-0049/199/2/29.

[Brinkworth2013-9] 7.0 ^7.1 MEASURING THE ROTATIONAL PERIODS OF ISOLATED MAGNETIC WHITE DWARFS. [2023-03-22]. （原始内容存档于2023-03-22）.

[note_1-6] From apparent magnitude and parallax.

[note_2-7] From surface gravity and mass.

[note_3-10] Cooling age, i. e. age as degenerate star (not counting duration of previous existence as main sequence star and as giant star)

[2]

[1]

[3]

[4]

[5]

[note 1]

[note 2]

[6]

[7]

[note 3]

觀測資料曆元 J2000^[1]
星座	天龍座
星官
赤經	17^h 48^m 08.17^s^[1]
赤緯	+70° 52′ 35.3″^[1]
視星等（V）	14.15^[2]
特性
光谱分类	DQP9.0^[2]
视星等 (B)	14.55^[1]
视星等 (V)	14.15^[1]
视星等 (R)	13.5^[1]
视星等 (I)	13.1^[1]
视星等 (J)	12.709 ± 0.021^[1]
视星等 (H)	12.528 ± 0.023^[1]
视星等 (K)	12.507 ± 0.023^[1]
天体测定

自行 (μ)	赤经：-1261^[3] mas/yr 赤纬：1112^[3] mas/yr
视差 (π)	160.9952 ± 0.0119^[4] mas
距离	20.259 ± 0.001 ly (6.2114 ± 0.0005 pc)
绝对星等 (M_V)	15.23^[2]^[5]^{[note 1]}

詳細資料

質量	0.81 ± 0.01^[2] M_☉
半徑	0.00984^[2]^{[note 2]} R_☉
表面重力 (log g)	8.36 ± 0.02^[2]
亮度	0.000085^[6] L_☉
溫度	5590 ± 90^[2] K
自轉	>100 years^[7]
年齡	5.69^{[note 3]}^[3] Gyr

其他命名
WD 1748+708,^[2]^[3] LHS 455,^[2] LP 44-113,^[1] NLTT 45565,^[1] GJ 1221,^[5] EGGR 372,^[1] 2MASS J17480817+7052353^[1]
參考資料庫
SIMBAD	资料
G 240-72 G 240-72 在天龍座的位置