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Twin Stars Born 500,000 Years Apart 引用】相差50万岁的双子星

已有 1773 次阅读2012-6-30 01:33 |个人分类:奇异空间|系统分类:科技教育分享到微信

这对叫做Par 1802的全等双子星（见插入框中）看起来就象一个单独的光点，因为在猎户座星云（见背景图）中它们彼此之间靠得太近了。

Twin Stars Born 500,000 Years Apart

Bouncing baby stars considered identical twins were oddly born 500,000 years apart, a new study finds.	一项新研究发现：一对处于婴儿期的巨型恒星被认为是全等双子星；但很奇怪，它们的诞生时间却相差50万年。
The newly discovered star pair is located in the Orion nebula, a nearby "maternity ward" bustling with stellar-birth activity and located 1,500 light-years from Earth. One light year is the distance light will travel in a year, or about 6 trillion miles (10 trillion kilometers).	这对新发现的恒星座落在猎户座星云之中。距离地球1500光年的猎户座星云就象附近的一个“恒星产房”，忙乱地进行着生产恒星的活动。1光年就是光在一年之中所穿行的距离，约相当于6万亿英里（10万亿公里）。
The astronomers who discovered the binary found that the stars show identical masses and compositions, elevating the pair to identical twin status. However, their relative brightness and other physical features differ, suggesting one star in Par 1802 formed earlier than the other.	观察到这对双子星的天文学家们发现，这两颗恒星显示出完全相同的质量和构成成分，使这对恒星上升到全等双子星的地位。然而它们的相对亮度及其他物理特性不同，这表明双星系统Par1802中一颗恒星的形成早于另一颗恒星。
Until now, astrophysicists had assumed binary stars form at about the same time. And so the discovery of these not-so-similar twin stars, detailed in the June 19 issue of the journal Nature, puts a new wrinkle in star formation theories.	在此之前，天体物理学家们一直以为双子星大致是同时形成的。可是这对双子星并非如此相似，因此详尽记录在6月19日出版的《自然》杂志上的这个发现，将一项创新写进了恒星形成理论之中。
Winking baby stars	闪烁的婴儿期恒星
Astronomers Keivan Stassun of Vanderbilt University and Robert Mathieu of the University of Wisconsin-Madison headed up the study.	范德比尔特大学的天文学家基凡·斯坦桑和威斯康星大学麦迪逊分校的天文学家罗伯特·马蒂厄主持了该研究。
They sifted through 15 years' worth of observations of thousands of stars, looking for stellar winks, which suggest a star has just eclipsed its partner. In eclipsing binaries, the two stars as viewed from Earth revolve around an axis that is edge-on to us. Periodically, the stars eclipse, or pass in front of, each other.	他们对长达15年的观测资料进行仔细审查，涉及到几千颗恒星，寻找闪烁的恒星——恒星闪烁说明一颗恒星刚刚遮挡了其伴星。在食双星的情况中，从地球上来看两颗恒星在围绕着一条侧向我们的轴旋转。两颗恒星周期性地出现互食现象，也就是说它们互相从彼此前面经过。
Sure enough, they saw a dip in light where the new eclipsing binary resides.	果然，研究人员在这对新发现的食双星座落的地方观察到光线变暗的情况。
Both stars are about 41 percent that of the sun's mass. Each star is about 1.7 to 1.8 times the size of the sun, though the astronomers estimate one could be about 10 percent larger than the other.	两颗恒星都大约是太阳质量的41%。尽管天文学家们估计一颗恒星可能比另一颗约大10%，但是每颗恒星都大约是太阳大小的1.7至1.8倍。
The observations come from the Kitt Peak National Observatory in Arizona and the SMARTS telescopes at the Cerro Tololo Inter-American Observatory in Chile.	这些观测是从亚利桑那州基特峰国家天文台进行的，而且还利用了智利托洛洛山美洲天文台的中小孔探察望远镜系统（SMARTS）。
Stellar genetics	恒星遗传学
Like humans' genetic material, mass and composition for stars can be akin to destiny, according to Stassun. Human identical twins, which come from the same egg, carry matching DNA and everything that comes with it, including spitting-image looks.	据斯坦桑说，类似人类的遗传物质，恒星的质量和构成成分也关乎其命运。人类中的同卵双生，来自同一个卵子，携带着相匹配的DNA以及随之而来的一切，包括一模一样的相貌。
And that's what astronomers would've assumed about two same-mass stars orbiting each other.	天文学家们对于两颗质量相同、互相环绕的恒星也是这样认为的。
"The mass of a star is the physical characteristic that, more than anything else, determines how the star will go through its life. Mass is destiny for a star," Stassun told SPACE.com. "If you have two stars with the same mass, their destinies ought to be the same. Or so we thought."	“质量是恒星的物理特征，该特征最有可能决定恒星将如何经历一生。质量就是恒星的命运，”斯坦桑告诉太空网的记者说，“如果两颗恒星质量相同，它们的命运应该是一样的，或者说我们原以为是一样的。”
Stassun and Mathieu found some glaring differences. One star is twice as bright as its sister. This showy twin also has a surface temperature that's about 300 degrees higher than its twin's.	斯坦桑和马蒂厄发现了一些明显的区别：一颗恒星的亮度是其伴星的两倍。在这对引人注目的双子星中，其中一颗的表面温度也比其孪生弟约高出300度。
Birth order	诞生的次序
These features make sense with a birth-order scenario suggested by the astronomers.	这些特征对于天文学家们提出的有关恒星诞生次序的设想具有意义。
Here's how they think it works:	天文学家们认为，设想情况是这样的：
Within Orion's stellar nursery, cloudlets of gas and dust are slowly collapsing in under their own weight, i.e. celestial conception. As the clumps of gas and dust condense and get smaller and smaller, they heat up until eventually they light up as full-fledged stars.	在猎户座的恒星孕育所里，由气体和尘埃构成的朵朵云团在其自身的重力作用下慢慢地塌缩，也就是相当于“天空中的孕育过程”。随着气体和尘埃云团的凝缩并变得越来越小，云团开始升温，直到最终亮起来成为发育成熟的恒星。
Most cloudlets pop out newborn stars at roughly the same time, Stassun said. But for the newly discovered twins, one star likely emerged roughly a half million year before its sibling.	斯坦桑说，多数云团大约在同一时间产出新生恒星。但是对于这对新发现的双子星来说，其中的一颗很可能比其同胞弟早诞生了约50万年。
That means the elder star would be slightly ahead of its sibling in the star-formation process and hence would have shed some of its heat and contracted more, explaining why one star (the elder) has a smaller size, lower temperature and glows fainter than the younger one. Since the older star has contracted more, it just crams the same mass into a smaller package.	这意味着，在形成过程方面，年龄较长的恒星可能稍早于其同胞弟，所以已经散失了其中的部分热量，而且收缩得也更多。这样就解释了为何其中一颗恒星（年龄较长的那颗）体积较小，温度较低，而且比起较年轻的那颗，光线也变得更暗淡。由于年龄较长的那颗恒星收缩更多，它在较小的包装空间内塞进了同等的质量。
"Our best interpretation at this point is that the reason we're seeing these physical differences is because there was a birth order between the twins," Stassun said. "One of them was born a little before the other one."	“在这一点上，我们给出的最令人满意的解释是：我们观察到这些物理特性的差别，其原因在于这对双子星在诞生次序上有先后之分，”斯坦桑说，“其中一颗比另一颗诞生得早一些。”
Stassun said they aren't sure "what was going on when the two stars were still in the womb; was one being fed more than the other?"	斯坦桑说：“我们还不能确定两颗恒星在孕育所时所发生的情况，是否一颗会比另一颗摄取的养分更多呢？”
Astronomers speculate stars tend to come in pairs, though eclipsing binaries are less common. And finding identical twins eclipsing, to boot, is like spotting that needle in a haystack, Stassun said.	天文学家们推测，尽管食双星并不太常见，但是恒星往往是成对出现的。然而斯坦桑表示，除了这对之外，要想发现互食的全等双子星无异于大海捞针。