显微镜座AU

显微镜座AU(AU Mic)是距离我们32.3光年(9.9秒差距)远,大约是离太阳最近距离恒星8倍远的一颗红矮星[4]。它的视星等为8.73 [2],这是太黯淡了,因此裸眼看不见它。因为它是在南天显微镜座的一颗变星,所以用变星命名法命名。如同老人增四(绘架座β)一样,它有一个岩屑盘的尘埃拱星盘环绕着。

显微镜座AU

显微镜座AU的岩屑盘。
观测资料
历元 J2000
星座 显微镜座
星官
赤经 20h 45m 09.53147s[1]
赤纬 –31° 20′ 27.2425″[1]
视星等(V) 8.73[2]
特性
光谱分类M1 Ve
U−B 色指数1.01
B−V 色指数1.45
变星类型[闪]焰星
天体测定
径向速度 (Rv)–6.0[2] km/s
自行 (μ) 赤经:+279.96[1] mas/yr
赤纬:-360.61[1] mas/yr
视差 (π)102.943 ± 1.06[1] mas
距离31.7 ± 0.3 ly
(9.7 ± 0.1 pc)
绝对星等 (MV)8.61
详细资料
质量0.31[3] M
半径0.84[3] R
亮度0.09[3] L
温度3,500 ± 100[3] K
自转速度 (v sin i)9.3[2] km/s
年龄12 ± 2[3] Myr
其他命名
CD -31°17815, GCTP 4939.00, GJ 803, HD 197481, HIP 102409, LTT 8214, SAO 212402, Vys 824, LDS 720 A.
参考数据库
SIMBAD资料
ARICNS资料

恒星的性质

显微镜座AU是一颗年轻的恒星,只有1,200万年的历史;还不到太阳年龄的1%[5]恒星光谱类型为M1Ve[2],是一颗红矮星[6]。它的半径为太阳的60%,尽管质量超过太阳的一半[7][8],它的辐射量只有太阳的9%[3],比太阳少了许多。这些能量从表面释出,温度只有3,700K[9],使它发出凉爽的橙红色光[10]。显微镜座AU是绘架座β移动星群的成员之一[11][12],它可能受到显微镜座AT重力约束,两者构成联星 [13]

无线电X射线,在所有的电磁频谱上都观察得到显微镜座AU,并且在所有的这些波段都观测到闪焰的活动[14][15][16][17]。这些闪焰在1973年首度被发现[18][19],在这些随机的爆发之后,其亮度几乎是正弦式变化,周期为4.865天,而振幅随时间的变化很缓慢。在1971年测量V波段的变化只有0.3星等;到1980年,更只有0.1星等[20]

行星系统

显微镜座AU的行星系[21][22][23]
成员
(依恒星距离)
质量 半长轴
(AU)
轨道周期
()
离心率 倾角 半径
b 36.9+1.72
−1.57
[24] M
0.066 8.46321+0.00004
0.1 89.03+0.12
−0.11
°
5.1 ± 0.17 R
c 32.1+2.3
−2.2
[25] M
0.1101+0.0022
18.858991+0.000010
88.62+0.24
−0.18
°
3.1 ± 0.16 R
e (未确认) 35.2+6.7
−5.4
M
? 33.39±0.10 ?
岩屑盘 <50 — >150 AU

岩屑盘

 
哈伯太空望远镜的显微镜座AU岩屑盘影像。
这段短片显示碎屑盘的图像。

在2003年,保罗·卡拉斯和他的研究伙伴首度使用夏威夷毛纳基山天文台2.2米口径的望远镜,在可见光的波段解析出显微镜座AU有尘埃的星周盘[4]这些大的岩屑盘以侧面朝向着地球疔潇。苽擭[26],测量到其半径至少有200天文单位距离恒星有如此大的距离疔潇。苽擭,盘中尘埃的寿命足以超过显微镜 AU现在的年龄[4]盘中气体和尘埃粒子的质量比率大约是疔潇。苽擭6:1,远低于通常假设的100:1的初始值[27],因此被归类为"缺乏气体"的岩屑盘估计在可见的盘中气体总量大约相当于月球的质量疔潇。苽擭,而当尘埃产生成更大的星子时,估计质量至少是月球的6倍[28]

显微镜座AU的光谱能量分布次微米波长上显示岩屑盘内有一个扩展到17天文单位的洞孔[29],而散射光的影像估计洞孔的半径是12天文单位[30]结合光谱能量分布和表面的亮度疔潇。苽擭,估计洞孔的半径更小,只有1-10天文单位[31]。 在40天文单位之内,盘的内部结构显示出是非对称[32],内部的结构已经与受到较大天体影响或最近有行星形成的比较,期望能看见更大的身影[32]

出现在内部的洞孔和不对称引导了很多的天文学家在此搜寻行星循着显微镜疔潇。苽擭 AU的轨道,迄2007年尚无任何可以导致行星的发现[31][33]

盘面上的表面亮度(单位面积的亮度)是从恒星的投影距离 和形状特性的函数在盘面内侧疔潇。苽擭15天文单位距离内的密度似乎是一个定值[30],大约 密度开始降低;开始减缓的较慢,大约是  此处 ;再往外 ,光度下降得更陡峭,大约是  ,此处 [30]这种疔潇。苽擭"破裂幂律"形状与绘架座β的盘面轮廓非常相似。

观测的方法

显微镜座AU的盘面已经被各种不同波段的波长观测过,给了我们这个系统不同型态的资讯在疔潇。苽擭光学波长下观测到的光线是恒星的光,它们被尘埃粒子反射(散射)进入我们的视线内观察这些波长时疔潇。苽擭,利用日冕仪遮版阻挡直接来自恒星的光,这样可以提供高分辨率的盘面影像因为波长比尘埃粒子直径大的光波不易被散射疔潇。苽擭,在不同的波长上比较(例如,可见光和红外线)就可以得知盘面上尘埃粒子尺寸大小的讯息[34]

 
艺术家对显微镜座AU的观点。创建者: NASA/ESA/G. Bacon (STScI)

哈伯太空望远镜凯克望远镜都曾用来进行光学的观测,也曾经使用红外线和次微米波观测过这个系统由尘埃粒子直接发射出的光线呈现出内热的结果疔潇。苽擭(修正黑体辐射),但在这种波长下无法解析出盘面,所以这样的观测只能测量来自系统整体的光观测的波长越长疔潇。苽擭,就能提供越大尘埃粒子的讯息,也观察到距离恒星越远的范围,这样的观测已经由詹姆士·克拉克·玛克斯威尔望远镜史匹哲太空望远镜完成。

参考资料

  1. ^ 1.0 1.1 1.2 1.3 1.4 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. ^ 2.0 2.1 2.2 2.3 2.4 Torres, C. A. O.; et al, Search for associations containing young stars (SACY). I. Sample and searching method, Astronomy and Astrophysics, December 2006, 460 (3): 695–708, Bibcode:2006A&A...460..695T, arXiv:astro-ph/0609258 , doi:10.1051/0004-6361:20065602 
  3. ^ 3.0 3.1 3.2 3.3 3.4 3.5 Plavchan, Peter; et al, New Debris Disks Around Young, Low-Mass Stars Discovered with the Spitzer Space Telescope, The Astrophysical Journal, June 2009, 698 (2): 1068–1094, Bibcode:2009ApJ...698.1068P, arXiv:0904.0819 , doi:10.1088/0004-637X/698/2/1068 
  4. ^ 4.0 4.1 4.2 Kalas, Paul; Liu, Michael C.; Matthews, Brenda C. Discovery of a Large Dust Disk Around the Nearby Star AU Microscopii. Science. 26 March 2004, 303 (5666): 1990–1992. Bibcode:2004Sci...303.1990K. PMID 14988511. arXiv:astro-ph/0403132 . doi:10.1126/science.1093420. 
  5. ^ Plavchan, Peter; Jura, M.; Lipsc, S. J. Where Are the M Dwarf Disks Older Than 10 Million Years?. The Astrophysical Journal. October 1, 2005, 631 (2): 1161–1169. Bibcode:2005ApJ...631.1161P. arXiv:astro-ph/0506132 . doi:10.1086/432568. 
  6. ^ Maran, S. P.; et al. An Investigation of the Flare Star AU Mic with the Goddard High Resolution Spectrograph on the Hubble Space Telescope. Bulletin of the American Astronomical Society. September 1991, 23: 1382. Bibcode:1991BAAS...23.1382M. 
  7. ^ Del Zanna, G.; Landini, M.; Mason, H. E. Spectroscopic diagnostics of stellar transition regions and coronae in the XUV: AU Mic in quiescence (PDF). Astronomy and Astrophysics. April 2002, 385 (3): 968–985 [2019-10-28]. Bibcode:2002A&A...385..968D. doi:10.1051/0004-6361:20020164. (原始内容存档 (PDF)于2017-08-09). 
  8. ^ Mouillet, David. Nearby Planetary Disks. Science. 26 March 2004, 303 (5666): 1982–1983. PMID 15044792. doi:10.1126/science.1095851. 
  9. ^ Linsky, J. L.; et al. Outer atmospheres of cool stars. XII - A survey of IUE ultraviolet emission line spectra of cool dwarf stars. The Astrophysical Journal. 15 September 1982, 260 (1): 670–694. Bibcode:1982ApJ...260..670L. doi:10.1086/160288. 
  10. ^ 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February 22, 2012) 
  11. ^ Zuckerman, B.; Song, Inseok. Young Stars Near the Sun. Annual Review of Astronomy & Astrophysics. September 2004, 42 (1): 685–721. Bibcode:2004ARA&A..42..685Z. doi:10.1146/annurev.astro.42.053102.134111. 
  12. ^ Barrado y Navascués, David; et al. The age of beta Pictoris. The Astrophysical Journal. August 1, 1999, 520 (2): L123–L126. Bibcode:1999ApJ...520L.123B. arXiv:astro-ph/9905242 . doi:10.1086/312162. 
  13. ^ Monsignori Fossi, B. C.; et al. The EUV spectrum of AT Microscopii. Astronomy & Astrophysics. October 1995, 302: 193. Bibcode:1995A&A...302..193M. 
  14. ^ Maran, S. P.; et al. Observing stellar coronae with the Goddard High Resolution Spectrograph. 1: The dMe star AU microscopoii. The Astrophysical Journal. 1 February 1994, 421 (2): 800–808. Bibcode:1994ApJ...421..800M. doi:10.1086/173692. 
  15. ^ Cully, Scott L.; et al. Extreme Ultraviolet Explorer deep survey observations of a large flare on AU Microscopii. The Astrophysical Journal. September 10, 1993, 414 (2): L49–L52. Bibcode:1993ApJ...414L..49C. doi:10.1086/186993. 
  16. ^ Kundu, M. R.; et al. Microwave observations of the flare stars UV Ceti, AT Microscopii, and AU Microscopii. The Astrophysical Journal. 15 January 1987, 312: 822–829. Bibcode:1987ApJ...312..822K. doi:10.1086/164928. 
  17. ^ Tsikoudi, V.; Kellett, B. J. ROSAT All-Sky Survey X-ray and EUV observations of YY Gem and AU Mic. Monthly Notices of the Royal Astronomical Society. December 2000, 319 (4): 1147–1153. Bibcode:2000MNRAS.319.1147T. doi:10.1046/j.1365-8711.2000.03905.x. 
  18. ^ Kunkel, W. E. Activity in Flare Stars in the Solar Neighborhood. The Astrophysical Journal Supplement. 1973, 25: 1. Bibcode:1973ApJS...25....1K. doi:10.1086/190263. 
  19. ^ Butler, C. J.; et al. Ultraviolet spectra of dwarf solar neighbourhood stars. I. Monthly Notices of the Royal Astronomical Society. December 1981, 197 (3): 815–827. Bibcode:1981MNRAS.197..815B. doi:10.1093/mnras/197.3.815. 
  20. ^ Butler, C. J.; et al. Rotational modulation and flares on RS CVn and BY DRA systems. II - IUE observations of BY Draconis and AU Microscopii. Astronomy and Astrophysics. March 1987, 174 (1–2): 139–157. Bibcode:1987A&A...174..139B. 
  21. ^ Addison, Brett C.; Horner, Jonathan; Wittenmyer, Robert A.; Plavchan, Peter; Wright, Duncan J.; Nicholson, Belinda A.; Marshall, Jonathan P.; Clark, Jake T.; Kane, Stephen R.; Hirano, Teruyuki; Kielkopf, John; Shporer, Avi; Tinney, C. G.; Zhang, Hui; Ballard, Sarah; Bedding, Timothy; Bowler, Brendan P.; Mengel, Matthew W.; Okumura, Jack; Gaidos, Eric, The Youngest Planet to Have a Spin-Orbit Alignment Measurement AU Mic B, The Astronomical Journal, 2021, 162 (4): 137, S2CID 220041674, arXiv:2006.13675 , doi:10.3847/1538-3881/ac1685 
  22. ^ EXOPLANET CATALOG AU Microscopii b on exoplanets.nasa.gov. [2023-04-17]. (原始内容存档于2021-06-14). 
  23. ^ Martioli, E.; Hébrard, G.; Correia, A. C. M.; Laskar, J.; Lecavelier Des Etangs, A., New constraints on the planetary system around the young active star AU Mic, Astronomy & Astrophysics, 2021, 649: A177, S2CID 229371309, arXiv:2012.13238 , doi:10.1051/0004-6361/202040235 
  24. ^ Cale, Bryson L.; et al. Diving Beneath the Sea of Stellar Activity: Chromatic Radial Velocities of the Young AU Mic Planetary System. The Astronomical Journal. 1 December 2021, 162 (6). 295. Bibcode:2021AJ....162..295C . arXiv:2109.13996 . doi:10.3847/1538-3881/ac2c80 . 
  25. ^ Wittrock, Justin M.; et al, Transit Timing Variations for AU Microscopii b and C, The Astronomical Journal, 2022, 164: 27, S2CID 245001008, arXiv:2202.05813 , doi:10.3847/1538-3881/ac68e5 
  26. ^ Paul Kalas, James R. Graham and Mark Clampin. A planetary system as the origin of structure in Fomalhaut's dust belt. Nature. 2005-06-23, 435 (7045): 1067–1070 [2008-10-24]. doi:10.1038/nature03601. (原始内容存档于2012-06-09). 
  27. ^ Aki Roberge, Alycia J. Weinberger, Seth Redfield, and Paul D. Feldman. Rapid Dissipation of Primordial Gas from the AU Microscopii Debris Disk. The Astrophysical Journal. 2005-06-20, 626 (2): L105–L108 [2008-10-24]. doi:10.1086/431899. (原始内容存档于2012-06-09). 
  28. ^ C. H. Chen, B. M. Patten, M. W. Werner, C. D. Dowell, K. R. Stapelfeldt, I. Song, J. R. Stauffer, M. Blaylock, K. D. Gordon, and V. Krause. A Spitzer Study of Dusty Disks around Nearby, Young Stars. The Astrophysical Journal. 2005-12-01, 634 (2): 1372–1384 [2008-10-24]. doi:10.1086/497124. (原始内容存档于2012-06-09). 
  29. ^ Michael C. Liu, Brenda C. Matthews, Jonathan P. Williams, and Paul G. Kalas. A Submillimeter Search of Nearby Young Stars for Cold Dust: Discovery of Debris Disks around Two Low-Mass Stars. The Astrophysical Journal. 2004-06-10, 608 (1): 526–532 [2008-10-24]. doi:10.1086/392531. (原始内容存档于2012-04-03). 
  30. ^ 30.0 30.1 30.2 John E. Kirst, D. R. Ardila, D. A. Golimowski, M. Clampin, H. C. Ford, G. D. Illingworth, G. F. Hartig, F. Bartko, N. Benítez, J. P. Blakeslee, R. J. Bouwens, L. D. Bradley, T. J. Broadhurst, R. A. Brown, C. J. Burrows, E. S. Cheng, N. J. G. Cross, R. Demarco, P. D. Feldman, M. Franx, T. Goto, C. Gronwall, B. Holden, N. Homeier, L. Infante, R. A. Kimble, M. P. Lesser, A. R. Martel, S. Mei, F. Mennanteau, G. R. Meurer, G. K. Miley, V. Motta, M. Postman, P. Rosati, M. Sirianni, W. B. Sparks, H. D. Tran, Z. I. Tsvetanov, R. L. White, AND W. Zheng. Hubble Space Telescope Advanced Camera for Surveys Coronagraphic Imaging of the AU Microscopii Debris Disk. The Astronomical Journal. February 2005, 129 (2): 1008–1017 [2008-10-24]. doi:10.1086/426755. (原始内容存档于2016-06-12). 
  31. ^ 31.0 31.1 Stanimir A. Metchev, Joshua A. Eisner, and Lynne A. Hillenbrand. Adaptive Optics Imaging of the AU Microscopii Circumstellar Disk: Evidence for Dynamical Evolution. The Astrophysical Journal. 2005-03-20, 622 (1): 451–462 [2008-10-24]. doi:10.1086/427869. (原始内容存档于2016-06-12). 
  32. ^ 32.0 32.1 Michael C. Liu. Substructure in the Circumstellar Disk Around the Young Star AU Microscopii. Science. 2004-09-03, 305 (5689): 1442–1444 [2008-10-24]. PMID 15308766. doi:10.1126/science.1102929. (原始内容存档于2012-04-03). 
  33. ^ E. Masciadri, R. Mundt, Th. Henning, and C. Alvarez. A Search for Hot Massive Extrasolar Planets around Nearby Young Stars with the Adaptive Optics System NACO. The Astrophysical Journal. 2005-06-01, 625 (2): 1004–1018 [2008-10-24]. doi:10.1086/429687. (原始内容存档于2016-06-12). 
  34. ^ Sanders, Robert. Dust around nearby star like powder snow. UC Berkeley News. 2007-01-08 [2007-01-11]. (原始内容存档于2007-01-15). 

外部链接