罰一

罰一 (天蝎座18) 是一顆距離地球45.3光年（13.9秒差距） 的孤獨恆星，他的位置在天蝎座北方的邊界處。他的視星等是5.5I，它有足夠的亮度可以在城市以外的地區以肉眼直接看見。 罰一有許多物理上的屬性與太陽相似。Cayrel de Strobel (1996) 在她審視恆星時將它列入類似太陽的恆星，並且Porto de Mello和da Silva (1997) 確定它為孿生太陽。因此，有些科學家相信在其附近有生命存在的前景看好。然而，迄今尚未發現這顆恆星有行星環繞著。 罰一是一顆主序星，光譜和光度分類為G2Va，光度分類為V指出它在核心地區經由氫的核融合產生能量。Sousa et al. (2008) 發現它的金屬量大約是太陽的1.1倍，這意味著除了氫或氦之外的元素豐度比太陽多了10% 。它的半徑，由Bazot et al. (2011) 使用干涉儀測量，是太陽半徑的101%。結合星震學測量的結果，估計這顆恆星的質量是太陽質量的102 %。測量這顆恆星表面的有效溫度是5,433K，因此他的輻射是太陽的106%。他的熱使這顆恆星事發出黃色色調的白炙G型恆星。 依據Lockwood (2002)，它瞬時光度的行為非常像太陽。在其整個活動週期，其亮度的變化只有0.09%，與目前太陽週期的光度變化大約相同。使用塞曼-都卜勒成像技術，Petit et al. (2008)已經測量到它表面的磁場，顯示其強度和幾何非常類似於太陽的磁場。估計它的活動周期大約是7年，這遠短於太陽，但是它整體的色球活動水準明顯的比太陽高。太陽相似，它有高溫的冕，溫度範圍在150-200萬K；X射線的發光度是8 ± 1.5 ergs s–1。 雖然罰一整體的金屬量只比太陽太陽略高一些，但它的鋰豐度大約是3倍；由於這個原因，Meléndez和Ramírez (2007)建議罰一可以稱為準太陽孿生，以與類太陽恆星有所區隔 (像是HIP56948)，它的所有參數，在誤差範圍之內，都與太陽完全吻合。 在2003年9月，罰一被來自亞利桑納土桑亞利桑那大學的太空生物學家瑪格麗特·特布林，基於它對適居恆星表清單的分析，選為最有希望培育生命的恆星。這是一顆孤獨的恆星，截至2005年，經由徑向速度的測量，尚未發現有行星環繞著它的跡象。這顆恆星也沒有過量的紅外線輻射，不足以建議它有鬆散的星周物質，像是岩屑盤的存在。 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  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  18 Sco -- Variable Star, SIMBAD (Centre de Données astronomiques de Strasbourg), [2011-10-13], （原始内容存档于2020-11-07）  The ubv information is per Compilation of Eggen's UBV data, transformed to UBV (unpublished) 1986. See the Measurements section. Hall, Jeffrey C.; et al, The Activity and Variability of the Sun and Sun-Like Stars. II. Contemporaneous Photometry and Spectroscopy of Bright Solar Analogs, The Astronomical Journal, July 2009, 138 (1): 312–322, Bibcode:2009AJ....138..312H, doi:10.1088/0004-6256/138/1/312  Bazot, M.; et al, The radius and mass of the close solar twin 18 Scorpii derived from asteroseismology and interferometry, Astronomy and Astrophysics, February 2011, 526, Bibcode:2011A&A...526L...4B, doi:10.1051/0004-6361/201015679  Sousa, S. G.; et al, Spectroscopic parameters for 451 stars in the HARPS GTO planet search program. Stellar [Fe/H] and the frequency of exo-Neptunes, Astronomy and Astrophysics, August 2008, 487 (1): 373–381, Bibcode:2008A&A...487..373S, arXiv:0805.4826 , doi:10.1051/0004-6361:200809698  Boyajian, Tabetha S.; et al, Stellar Diameters and Temperatures. I. Main-sequence A, F, and G Stars, The Astrophysical Journal, February 2012, 746 (1): 101, Bibcode:2012ApJ...746..101B, arXiv:1112.3316 , doi:10.1088/0004-637X/746/1/101 . See Table 10. Coughlin, Jared; et al, The Night Time Sun: X-Ray Observations of the Solar Twin 18 Scorpii, Bulletin of the American Astronomical Society, January 2010, 42: 333, Bibcode:2010AAS...21542417C  Mamajek, Eric E.; Hillenbrand, Lynne A., Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics, The Astrophysical Journal, 2008, 687 (2): 1264–1293, Bibcode:2008ApJ...687.1264M, arXiv:0807.1686 , doi:10.1086/591785  Cayrel de Strobel, G., Stars Resembling the Sun, The Astronomy and Astrophysics Review, 1996, 7 (3): 243–288, Bibcode:1996A&ARv...7..243C, doi:10.1007/s001590050006  Porto de Mello, G. F.; da Silva, L., HR 6060: The Closest Ever Solar Twin?, The Astrophysical Journal, 1997, 482 (2): L89–L92, Bibcode:1997ApJ...482L..89P, doi:10.1086/310693  A metallicity of [Fe/H] = 1.04 dex indicates that the star has 100.04 = 1.096, or 110% of the abundance of elements heavier than helium, compared to the Sun. The Colour of Stars, Australia Telescope, Outreach and Education (Commonwealth Scientific and Industrial Research Organisation), December 21, 2004 [2012-01-16], （原始内容存档于2012-03-10）  Lockwood, G. W.; et al, Gauging the Sun: Comparative photometric and magnetic activity measurements of sunlike stars, 1984-2001 (PDF), Bulletin of the American Astronomical Society, May 2002, 34: 651, Bibcode:2002AAS...200.0709L, （原始内容 (PDF)存档于2006-09-05）  Hall, J. C.; Lockwood, G. W., The Sun-Like Activity of the Solar Twin 18 Scorpii, The Astronomical Journal, 2007, 133 (5): 2206–2008, Bibcode:2007AJ....133.2206H, arXiv:astro-ph/0703450 , doi:10.1086/513195  Petit, P.; et al, Toroidal versus poloidal magnetic fields in Sun-like stars: a rotation threshold, Monthly Notices of the Royal Astronomical Society, 2008, 388 (1): 80, Bibcode:2008MNRAS.388...80P, arXiv:0804.1290 , doi:10.1111/j.1365-2966.2008.13411.x  Hall, Jeffrey C.; Lockwood, G. W., Evidence of a Pronounced Activity Cycle in the Solar Twin 18 Scorpii, The Astrophysical Journal, 2000, 545 (2): L43–L45, Bibcode:2000ApJ...545L..43H, doi:10.1086/317331  Meléndez, J.; Ramírez, I., HIP 56948: A Solar Twin with a Low Lithium Abundance, The Astrophysical Journal, 2007, 669 (2): L89–L92, Bibcode:2007ApJ...669L..89M, arXiv:0709.4290 , doi:10.1086/523942  Marcy, Geoffrey W.; et al, Five New Extrasolar Planets, The Astrophysical Journal, 2005, 619 (1): 570–584, Bibcode:2005ApJ...619..570M, doi:10.1086/426384  Lawler, S. M.; et al, Explorations Beyond the Snow Line: Spitzer/IRS Spectra of Debris Disks Around Solar-type Stars, The Astrophysical Journal, November 2009, 705 (1): 89–111, Bibcode:2009ApJ...705...89L, arXiv:0909.0058 , doi:10.1088/0004-637X/705/1/89  Kaler, James B., 18 Scorpii, Stars (University of Illinois), [2012-03-06], （原始内容存档于2021-04-15）  NASA article on 18 Scorpii（页面存档备份，存于互联网档案馆） 18 Scorpii entry in the stellar database （页面存档备份，存于互联网档案馆） Astronomers Measure Sun-Like Brightness Changes of the Solar Twin, 18 Scorpii