天弁二
觀測資料 曆元 J2000 | |
---|---|
星座 | 盾牌座 |
星官 | |
赤經 | 18h 42m 16.422137s[1] |
赤緯 | −09° 03′ 09.19206″[1] |
視星等(V) | 4.60 - 4.79[2] |
特性 | |
光譜分類 | F2 IIIp[3] |
U−B 色指數 | +0.16[4][2] |
B−V 色指數 | +0.35[4] |
變星類型 | 盾牌座δ |
天體測定 | |
徑向速度 (Rv) | −44.8[5] km/s |
自行 (μ) | 赤經:9.21[1] mas/yr 赤緯:0.82[1] mas/yr |
視差 (π) | 16.11 ± 0.31[1] mas |
距離 | 202 ± 4 ly (62 ± 1 pc) |
絕對星等 (MV) | ±0.04 0.72[6] |
詳細資料 | |
質量 | +0.06 −0.05 2.23[7] M☉ |
表面重力 (log g) | 3.5[8] |
溫度 | 7000[8] K |
金屬量 [Fe/H] | 0.41[6] dex |
自轉速度 (v sin i) | 25.5[8] km/s |
年齡 | ±0.1 0.7[6] Gyr |
其他命名 | |
參考資料庫 | |
SIMBAD | 資料 |
天弁二(盾牌座δ)是在南天盾牌座的一顆巨星,視星等4.72等[4],是在這個小且沒有特徵星座的第五亮星。分析依巴谷衛星任務期間測量的視差,這顆恆星與地球的距離大約是202光年(62秒差距)[1]。天弁二是盾牌座δ變星的原型,這種變星來自體積脹縮造成光度的高振幅大約都在0.15星等左右。這顆恆星特有的化學豐度與Am星相似[8]。
在1900年,天文學家威廉·華萊士·坎貝爾(William Wallace Campbell)和威廉·哈蒙德·賴特使用利克天文台的米爾斯光譜儀確定該恆星的徑向速度會變化[10]。在1935年,測量出光度以77日(4.65小時)的週期有着0.2等(在+4.60至+4.79之間變化)的振幅,並證實這種變化是內在的,而不是 0.193光譜聯星造成的結果[11]。在1938年,發現了次要的週期,並提出脈動理論來模擬這種變異[12]。之後對天弁二的觀測表明,它是在多重離散的徑向和非徑向模式下脈動。模式最強的頻率是59.731μHz,其次是61.936μHz,依此類推,現在共建模了八種不同的頻率模式[13]。
這顆恆星在銀道坐標系的空間速度是[U, V, W] = [–42, –17, –1] km·s−1。它以離心率0.11的軌道繞行銀河系,最接近銀河中心的距離是22.31 kly(6.84 kpc),最遠的距離是27.59 kly(8.46 kpc)[6]。如果天弁二維持現在的運動和光度,它將以10光年的距離內經過太陽系附近[14],並且在西元150000至 1330000 CE成為天空中最亮的恆星,視星等為-1.84,比 1天狼星現在的-1.46還要明亮[15]。
天弁二有二顆光學伴星。第一顆距離15.2角秒,視星等+12.2。第二顆距離53角秒,視星等+9.2[16]。
佛蘭斯蒂德沒有將天弁二標示在盾牌座,而是將它與其它幾顆星納入天鷹座,並在星表中標記為天鷹座2。拜耳名稱的盾牌座δ是由古德命名的[17]。
參考資料
- ^ 1.0 1.1 1.2 1.3 1.4 1.5 van Leeuwen, F., Validation of the new Hipparcos reduction, Astronomy and Astrophysics, November 2007, 474 (2): 653–664, Bibcode:2007A&A...474..653V, arXiv:0708.1752
, doi:10.1051/0004-6361:20078357
- ^ 2.0 2.1 Samus, N. N.; Durlevich, O. V.; et al. VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013). VizieR On-line Data Catalog: B/gcvs. Originally published in: 2009yCat....102025S. 2009, 1. Bibcode:2009yCat....102025S.
- ^ Cowley, Anne; Fraquelli, Dorothy, MK Spectral Types for Some Bright F Stars, Publications of the Astronomical Society of the Pacific, February 1974, 86 (509): 7, Bibcode:1974PASP...86...70C, doi:10.1086/129562
- ^ 4.0 4.1 4.2 Johnson, H. L.; et al. UBVRIJKL photometry of the bright stars. Communications of the Lunar and Planetary Laboratory. 1966, 4 (99): 99. Bibcode:1966CoLPL...4...99J.
- ^ Evans, D. S. The Revision of the General Catalogue of Radial Velocities. Batten, Alan Henry; Heard, John Frederick (編). Determination of Radial Velocities and their Applications, Proceedings from IAU Symposium no. 30. University of Toronto: International Astronomical Union. June 20–24, 1966. Bibcode:1967IAUS...30...57E.
- ^ 6.0 6.1 6.2 6.3 Holmberg, J.; Nordström, B.; Andersen, J., The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics, Astronomy and Astrophysics, July 2009, 501 (3): 941–947, Bibcode:2009A&A...501..941H, arXiv:0811.3982
, doi:10.1051/0004-6361/200811191
- ^ Nordström, B.; et al, The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of ˜14 000 F and G dwarfs, Astronomy and Astrophysics, May 2004, 418: 989–1019, Bibcode:2004A&A...418..989N, arXiv:astro-ph/0405198
, doi:10.1051/0004-6361:20035959
- ^ 8.0 8.1 8.2 8.3 Yushchenko, A.; et al. The chemical composition of δ Scuti. Monthly Notices of the Royal Astronomical Society. May 2005, 359 (55): 865–873. Bibcode:2005MNRAS.359..865Y. doi:10.1111/j.1365-2966.2005.08921.x.
- ^ del Sct – Variable star of delta Sct type. SIMBAD Astronomical Object Database. Centre de Données astronomiques de Strasbourg. [2009-10-23]. (原始內容存檔於2020-11-05).
- ^ Campbell, W. W.; Wright, W. H. A list of nine stars whose velocities in the line of sight are variable. Astrophysical Journal. 1900, 12: 254–257. Bibcode:1900ApJ....12..254C. doi:10.1086/140765. Listed as 2 Scuti on p. 256.
- ^ Colacevich, A. On the variable radial velocity of δ Scuti. Publications of the Astronomical Society of the Pacific. August 1935, 47 (278): 231–232. Bibcode:1935PASP...47..231C. doi:10.1086/124599.
- ^ Sterne, T. E. The Secondary Variation of δ Scuti. Astrophysical Journal. March 1938, 87: 133–150. Bibcode:1938ApJ....87..133S. doi:10.1086/143913.
- ^ Templeton, Matthew R.; et al. A New Pulsation Spectrum and Asteroseismology of delta Scuti. The Astronomical Journal. October 1997, 114: 1592–1601. Bibcode:1997AJ....114.1592T. doi:10.1086/118590.
- ^ García-Sánchez, J.; et al, Stellar encounters with the solar system, Astronomy and Astrophysics, 2001, 379 (2): 634–659, Bibcode:2001A&A...379..634G, doi:10.1051/0004-6361:20011330
- ^ Sky and Telescope, April 1998 (p60), based on computations from Hipparcos mission data.
- ^ Burnham, Robert. Burnham's celestial handbook: an observer's guide to the universe beyond the solar system 3. Courier Dover Publications. 1978: 1746. ISBN 0-486-23673-0.
- ^ Wagman, M. Flamsteed's Missing Stars. Journal for the History of Astronomy, Vol.18, NO. 3/AUG, P.209, 1987. August 1987, 18: 212. Bibcode:1987JHA....18..209W. doi:10.1177/002182868701800305.
外部連結
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