极端海王星外天体

极端海王星外天体ETNO,extreme trans-Neptunian object)是在太阳系最外层的海王星(30AU)之外绕太阳运行,半长轴至少为150–250 AU的海王星外天体[1][2]。与所有其它已知的海王星外天体相比,极端海王星外天体的轨道受已知巨行星的影响要小得多。然而,它们可能会受到与假想的第九行星的引力相互作用的影响,将这些物体引导到同类型的类似轨道[1]。已知的极端海王星外天体在具有较小升交点和降交点距离的天体对的分布之间,表现出高度统计显著的不对称性,这可能表明受到外部扰动的响应[3][4]

上图描绘了海王星外天体近日点在海王星外(超过30 AU)的关系。此处,常规的海王星外天体(TNO)位于图的左下角,极端海王星外天体(ETNO)的半长轴大于150–250 AU。它们可以根据其近日点分为三个不同的族群[1]
  离散的ETNOs或ESDOs (38–45 AU)
  孤立的ETNOs或EDDOs (40–45与50–60 AU)
  类赛德娜天体或内欧特云天体(超过 50–60 AU)

极端海王星外天体可分为三个不同的子群。离散盘天体(或极端散射盘天体,ESDOs)的近日点大约在38–45 AU和超过0.85的异常高偏心率。与常规的离散盘天体一样,它们很可能是由海王星引力散射形成的,并且仍然与巨行星相互作用。孤立 海王星外天体(或极端分离圆盘天体,EDDO),近日点大约在40-45和50-60之间 AU受海王星的影响比离散盘天体的海王星外天体小,但仍然相对靠近海王星。类赛德娜天体希尔斯云天体,近日点超过 50–60 AU,离海王星太远,不会受到它的强烈影响[1]

类赛德娜天体

 
The orbits of Sedna2012 VP113Leleākūhonua,和其它非常遥远的天体轨道,以及第九行星的预测轨道[A]

在极端的海王星外天体中,有类赛德娜天体(英语:sednoids),这四颗天体具有非常大的近日点距离:赛德娜2012 VP113541132 Leleākūhonua、和2021 RR205。赛德娜和2012 VP113是近日点大于70 AU的远距离独立天体。它们的大近日点距离使它们保持足够的距离,避免了来自海王星的显著引力扰动。以前对赛德娜大近日点距离的解释包括:在遥远的轨道上与未知行星的近距离相遇,以及与随机恒星或太阳诞生星团成员的遥远相遇,该恒星或太阳诞生星团的成员在太阳系附近经过[5][6][7]

离太阳最远的天体

楚希罗和雪柏的发现

天文学家查德·楚希罗史考特·桑德·雪柏发现的极端海王星外天体包括:

  • 2013 FT28近日点经度与第九行星对齐,但完全在第九行星的拟议轨道内,计算机建模表明它不会受到引力的冲击[8]
  • 2014 SR349:似乎与第九行星相反[8]
  • 2014 FE72:一个轨道非常极端的天体,它以一个巨大的拉长椭圆到达距离太阳约3,000天文单位的天体。在这个距离上,它的轨道受到银河系潮汐和其它恒星的影响[9][10][11][12]

外太阳系起源调查

外太阳系起源调查发现了更极端的海王星外天体,包括[13]

  • 2013 SY99:由蜜雪儿·班尼斯特(Michele Bannister)发现,它的倾角比许多物体都低。在2016年3月由SETI协会主办的讲座上讨论过,后来在2016年10月AAS的会议也讨论过[14][15]
  • 2015 KG163:它的方向与2013 FT28相似,但有一个更大的半长轴,可能导致它的轨道穿过第九行星的轨道。
  • 2015 RX245:它适合其它反对齐物件。
  • 2015 GT50:既不属于反对齐天体,也不属于对齐天体;相反的,它的轨道方向与拟议的第九行星的方向成直角。它关于近日点的参数也超出了近日点参数的集群。

自2016年初以来,又发现了10个极端海王星外天体,其轨道的近日点大于30 AU 和半长轴大于 250;使非对齐天体总数达到16颗(完整清单见下表)。大多数海王星外天体(TNO)的近日点明显超出海王星绕太阳运行的30 AU[16][17]。一般来说,近日点小于36 AU的海王星外天体会与海王星发生强烈的相遇[18][19]。大多数海王星外天体相对较小,但因为它们在椭圆轨道上接近与太阳的最近距离,因此目前相对明亮。这些天体也包含在下面的轨道图和表格中。

TESS数据搜索

Malena Rice和Gregory Laughlin应用了一种有针对性的移位堆叠搜索算法分析来自TESS扇区18和19的数据,寻找候选的太阳系外天体[20]。他们的搜索恢复了像赛德娜这样的已知海王星外天体,并产生了17个新的太阳系外天体候选者,这些天体位于80-200天文单位的地心距离范围内,需要地面望远镜资源进行后续观测才能确认。WHT旨在恢复这些遥远的海王星外天体的候选者,但未能确认其中两个[21][22]

清单

最极端的例子是2015 BP519,绰号“Caju”,它具有最高的倾角[23],和最远的节点距离;这些属性使其成为该群中可能的异常值[2]

注解

  1. ^ 三颗类赛德娜天体(粉红色)和红色的极端海王星外天体(ETNO)轨道被怀疑与假设的第九行星对齐,而蓝色的ETNO轨道是反对齐的。被染成棕色的高度拉长的轨道包括半人马小行星和达摩克型小行星,它们的远日点距离超过200 AU.

参考资料

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  2. ^ 2.0 2.1 de la Fuente Marcos, Carlos; de la Fuente Marcos, Raúl. A Fruit of a Different Kind: 2015 BP519 as an Outlier among the Extreme Trans-Neptunian Objects. Research Notes of the AAS. 12 September 2018, 2 (3): 167. Bibcode:2018RNAAS...2..167D. S2CID 119433944. arXiv:1809.02571 . doi:10.3847/2515-5172/aadfec . 
  3. ^ de la Fuente Marcos, Carlos; de la Fuente Marcos, Raúl. Peculiar orbits and asymmetries in extreme trans-Neptunian space. Monthly Notices of the Royal Astronomical Society. 1 September 2021, 506 (1): 633–649 [2024-04-17]. Bibcode:2021MNRAS.506..633D. arXiv:2106.08369 . doi:10.1093/mnras/stab1756. (原始内容存档于2021-10-19). 
  4. ^ de la Fuente Marcos, Carlos; de la Fuente Marcos, Raúl. Twisted extreme trans-Neptunian orbital parameter space: statistically significant asymmetries confirmed. Monthly Notices of the Royal Astronomical Society Letters. 1 May 2022, 512 (1): L6–L10 [2024-04-17]. Bibcode:2022MNRAS.512L...6D. arXiv:2202.01693 . doi:10.1093/mnrasl/slac012. (原始内容存档于2023-04-09). 
  5. ^ Wall, Mike. A Conversation With Pluto's Killer: Q & A With Astronomer Mike Brown. Space.com. 24 August 2011 [7 February 2016]. (原始内容存档于2016-02-02). 
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