One Planet, Two Parents?

beimu1009 · 发表于 2009-10-9 09:24:58

天文学家发现一颗地外行星轨道诡异，很有可能是在两颗恒星的引力作用下形成的，而不是通常的单一中央恒星。
行星HD80606b距离地球大约190光年，是一颗4倍于木星质量的气态行星，围绕双星系统中的一颗恒星运动。天文学家推测它与众不同的轨道可能受距离2千亿千米之外的另一颗恒星的影响。但缺乏确凿的证据。因此从马萨诸塞州到夏威夷的8名天文学家跟踪了这颗行星凌日（从恒星前方通过）时的位置，将每一台望远镜获得的部分数据拼接起来，证实了之前的推测。报告发表在《天体物理学杂志》上。HD 80606b是至今观察到的第一颗有两个母星的行星例子，它属于一种新类型的地外行星。

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ScienceNOW：
http://sciencenow.sciencemag.org/cgi/content/full/2009/1006/3?rss=1#comment-block

One Planet, Two Parents?By Phil Berardelli
ScienceNOW Daily News
6 October 2009
Astronomers have found that an extrasolar planet's orbit is soelongated and tilted that its path was probably gravitationally shapedby two stars instead of the usual, single central star. The discoveryrepresents the first example of a new category of alien worlds.Located about 190 light-years from Earth, the planet HD 80606b is a gasgiant four times more massive than Jupiter. The planet's unusual orbitgrazes its parent star and also swings it out to nearly the distancebetween Earth and our sun. Even stranger, that orbit is tilted highabove the star's equator and axis of rotation. After the planet wasdiscovered in 2001, astronomers had speculated that these bizarrecharacteristics were caused by the gravitational interference of thestar's binary partner, located less than 200 billion kilometers away.But they lacked conclusive evidence.
So astronomers at eight observatories from Massachusetts to Hawaiitracked the planet over 11 hours as it passed in front of its star. Thestar appeared shortly after sundown at each location and remainedvisible only for a couple of hours, so each telescope could contributeonly a portion of the data.
Based on those observations, reported in the current issue of The Astrophysical Journal,the authors confirm what astronomers had been thinking about HD 80606b.Previous predictions are "exactly what was observed" by the researchteam, says astronomer Greg Laughlin of the University of California,Santa Cruz, who was not affiliated with the study. If that's the case,HD 80606b opens the ledger of a new type of exoplanet, one that isgravitationally linked to two stars.
The multiple-telescope approach "will become more common and indeednecessary to study other long-transiting planets with large orbitalperiods," says astronomer and co-author Eric Ford of the University ofFlorida, Gainesville. It's particularly true in the search forEarth-like planets in the habitable zone around stars, he says, whichwill have similar transit times.
Planetary scientist Jack Lissauer of NASA's Ames Research Center atMoffett Field, California, says that, based on his own solar systemmodeling research, the team's conclusion is the most plausibleexplanation for HD 80606b's strange orbit. It's possible that HD 80606bcould have been gravitationally perturbed by a neighboring massiveplanet and kicked into its current orbit, he says, but this is unlikelygiven the presence of the companion sun.