Spitzer090420：围绕白矮星运转的太阳系外类地行星

原文发表有半个月了，由于翻译工作量太多，搁置到今天才开始。计划在3天内完成它。原文出处
http://www.spitzer.caltech.edu/Media/happenings/20090420/

由于Spitzer的分辨率比不上哈勃，而且很快差距将更大。本文的附图几乎都是艺术概念图。从下一楼开始正文。

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Rocky Planets Around 'Dead' Stars
围绕“死亡”恒星转的岩质行星
Written by Raphael Rosen，April 20, 2009
作者：拉斐尔.罗森  2009.4.20

Using the infrared detectors on NASA's Spitzer Space Telescope, a team of researchers based in the U.K. and in the United States have placed new constraints on how often rocky planets like Earth may exist around stars other than our Sun.
基于美国宇航局斯必泽太空望远镜的红外观测结果，美英两国学者组成的研究团队给出了像太阳这样的恒星附近存在类地行星的新的约束条件。（最后这个词等我全文译完再改为更合适的——译注）
The team of researchers, including Jay Farihi, from the Universityof Leicester; and Michael Jura and Ben Zuckerman, both from UCLA,looked at the environments surrounding a number of "dead" stars known as a "white dwarfs". Using Spitzer's sensitive infrared eyes, they found that at least 1-3% of all white dwarf stars of a certain age are surrounded by dust and rocky debris.
团队成员包括：英国莱斯特大学的杰.Farihi，加利福尼亚大学洛杉矶分校的迈克尔.侏罗和本.朱克曼，他们把研究目光投向“死亡”恒星——白矮星附近的（空间）环境。经斯必泽太空望远镜的红外观测，他们发现这些不算年轻的白矮星中，至少1%~3%的比例有尘埃和岩质行星残骸在围绕它们旋转。
"The infrared glow from dust around these white dwarfs is a road sign that tells us there were — or are — unseen rocky planets in these systems," said Farihi.
杰.Farihi说：“白矮星旁尘埃的红外辉光是个路标，告诉我们那个恒星系统里有——或者曾经有看不见的岩质行星。”
The team believes that the dust was produced when asteroids - the building blocks of rocky planets - surrounding the star were pushed and pulled apart by the force of the star's gravity. The dust then formed a glowing disk of orbiting, rocky material that Spitzer detected.
团队成员相信，尘埃形成于围绕恒星的小行星群——构建岩质行星的“积木”——被恒星的强大引力压缩拉扯（分裂）的时候，然后它们形成灼热的岩石碎片带而被斯必泽太空望远镜探测到。

                               
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Just how common are rocky bodies around white dwarfs? In a previous study by this team, a sample of eight white dwarfs were shown to have the dusty remnants of shredded asteroids. In this study Farihi and his team systematically searched around metal-rich white dwarfs and placed statistical constraints on the frequency of inferred rocky planets.
那么白矮星周围的岩质行星到底有多普遍呢？根据这个团队的先前研究，样本中的8个白矮星显示它们具有由小行星碎片构成的尘埃（环）。在这个研究中，Farihi团队系统地搜寻了富含金属的白矮星周围，统计并推断出岩质行星的比例（规律）。
"We now know of 14 white dwarfs circled by dusty debris. This suggests that at least 1-3% of main-sequence A and F stars — stars slightly hotter and larger than the Sun — have rocky planets, like Earth," said Farihi.
“现在我们发现了14个白矮星环绕有尘埃碎片。这相当于1%~3%的主序星A和F——比太阳大一些和热一些的恒星具有类地行星，”杰.Farihi说。
  For the rocky bodies to be destroyed by the gravitational effects of the white dwarf, they would have to be knocked out of their orbits,towards the star. Farihi and his team believe that, although in principle this kick could come from a terrestrial planet, a large gas giant planet like Jupiter would do the job much more efficiently.Therefore, the small percentage of white dwarfs that might possess rocky planets probably have larger, gas-giant-like planets as well.
由于白矮星的引力效应会扯碎岩石(小行星)碎片，它们将被撞出轨道并逐步落向白矮星。Farihi团队相信，虽然这种剔出效应可由类地行星造成，但一个大型气态巨行星——类木行星做此事会高效得多。因此，虽然只有小比例的白矮星具有岩质行星，（更多的）却可能会有大型气态行星。

PS：人名实在很有趣，jay是松鸡哦，而Jura，大家知道著名的侏罗纪公园吧？主序星最热的是O型和B型，都是蓝(紫)巨星，A,F型是白色、黄白色的，太阳是G型。最后一段的英文貌似词不达意，从后句来看，显然说的是大行星对小行星带的引力摄动作用，但前段的主词是白矮星white dwarf而不是行星 planet 啊？！
严格意义上，terrestrial planet才是类地行星；从本文的上下文看，虽然rocky planet直译是岩质行星，但也被指代类地行星。为更准确的传递原文意思，我翻译时只有“rocky planets, like Earth”类的才译为类地行星，其余的还是采用岩质行星名称。——gohomeman1

   这是啥呀~~~~~

继续翻译下去
Rocky Planets Around 'Dead' Stars
围绕“死亡”恒星转的岩质行星
Written by Raphael Rosen，April 20, 2009
作者：拉斐尔.罗森  2009.4.20

White dwarfs are the remnants of relatively low-mass stars that have passed through their red giant stage. Stars are composed mostly of hydrogen, and, during their lives, they burn more and more of the hydrogen, converting hydrogen into helium, until very little hydrogen is left. Then, the star begins to burn helium to create even heavier elements. When the supply of helium runs out, the star burns heavier and heavier elements, until it produces iron, which cannot be burned.
白矮星是那些相对中小质量恒星经历红巨星阶段后的残余。恒星一开始大部分由氢组成，在它们的生命历程中，聚变越来越多的氢成氦，直到只剩下很少的氢。接着，恒星开始聚变氦产生更多的重元素。当氦也逐渐耗尽时，恒星就聚变重元素产生更重的元素，直到它们合成铁，一种不能继续聚变的元素。（PS：这是简单的说法，其实不同的恒星历程完全不同，而且也不是都能聚变到铁的。最后形成白矮星的恒星，一般核心聚变到C、O，最多O再吸收He形成Ne,远远未到形成Fe。由于铁Fe是结合能最大的原子核，继续聚变将吸收能量而不是放出热量——译注）
At this point, the star's contraction — due to its gravity — and its expansion — due to the energy produced by its thermonuclear reactions — become unbalanced, and the outer layers of the star puff out. Over time, the layers blow out into space, leaving behind a small core, which, because of the extreme gravity, compresses until it is extraordinarily dense. This core is called a "white dwarf."
此时，由引力产生的收缩压与由热核反应释放能量产生的膨胀压失去平衡，其外层气壳被是吹散。随着时间流逝，外层气壳膨胀消散在太空中，留下一个很小但因引力收缩而相当致密的核心——“白矮星”。（此处其实过程也比较复杂，中等以上质量的恒星在其核心收缩为白矮星时，外部气壳坠落过程中遇到致密的核心后反弹，瞬间点燃了外壳的聚变反应而炸开，谓之新星；但小于太阳质量一半的恒星，其外壳收缩并不能点燃核反应，这样就直接出现外层大气持续膨胀而内部直接收缩的情形，这时就不会观测到新星了——译注）

                               
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A white dwarf may be the size of the Earth, but contain the same mass as the Sun. This star remnant is so dense, in fact, that one teaspoon of white dwarf material would weigh several tons. Over 90% of all stars — including our Sun — will end their lives as white dwarfs.
白矮星可能只有地球大小，但包含的质量可能与太阳相当（其质量上限是1.3~1.45倍太阳）。事实上，白矮星的物质非常致密，1茶匙物质就有数吨重（比中子星还是轻得多）。90%以上的恒星——包括我们的太阳的生命终点都是白矮星。
According to Farihi and his team, studying white dwarf stars is a good way to study planetary systems outside of our own Solar System. First, a white dwarf star is relatively dim and small -so its heat won't outshine the heat emitted by giant planets or dust orbiting it. Second, white dwarf stars do not contain significant amounts of heavy elements, like metals, so if metals are detected in a white dwarf, one can assume that the white dwarf has been absorbing those elements from surrounding debris. This permits an indirect way of studying the composition of distant planets.
根据Farihi团队的研究，白矮星周围的行星系统是了解太阳系外行星的一个好途径。首先，白矮星相对来说又小又暗，它的辐射不比巨行星或者尘埃亮多少；其次，白矮星不包含大量的重元素——比如金属元素，所以如果在白矮星光谱中发现金属元素，我们可以假设它们是白矮星从周围的残骸中吸收的。这样就可以间接的研究遥远行星的化学成分了。

This research paper was written by Jay Farihi, at the University of Leicester, UK; and Michael Jura and Ben Zuckerman, both at UCLA.
本研究报告作者：英国莱斯特大学的杰.Farihi，加利福尼亚大学洛杉矶分校的迈克尔.侏罗和本.朱克曼。
This research was supported by NASA, through an award issued by JPL/Caltech to UCLA, and has also been partly supported by the National Science Foundation.
本研究经费由美国宇航局透过加州理工学院喷气推进实验室给予加州大学洛杉矶分校，另一部分经费由自然科学基金会提供。
Team member Professor Jay Farihi of the University of Leicester presents this discovery on Monday 20th April at the European Week of Astronomy and Space Science conference at the University of Hertfordshire. Visit http://www.ras.org.uk for an associated press release from the Royal Astronomical Society.
4.20周一，在英国赫特福德大学举行的欧洲天文学和宇宙学周会上，团队成员杰.Farihi教授（莱斯特大学）公布了本发现。由英国皇家天文学会授权的美联社新闻稿可以在下面网站找到：（复杂的版权关系——译注）
http://www.ras.org.uk

文字中貌似没说清啊，等我把另外2个短文一起翻译了再看。一般估计是单独得恒星吧。剩下的2篇文章还没看呢。

不错的说 顶一下！

本文的2个附图说明
http://gallery.spitzer.caltech.edu/Imagegallery/image.php?image_name=sig09-002

Emission from the White Dwarf System GD 16
白矮星GD 16系统的光谱

                               
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This chart shows the brightness and wavelength of the radiation coming from white dwarf GD 16 and its associated disk of closely orbiting rocky material. The data was obtained with NASA's Spitzer Space Telescope. The colored data points indicate hot emission from the white dwarf (left of the graph) and cool emission from the surrounding material (right hand side).
本图表是白矮星GD 16及其关联的岩石物质盘的光谱—亮度示意图，数据由斯皮策太空望远镜获取。彩色点表示辐射采样点，左图部分是白矮星的热辐射，右图是周围物质相对较冷的辐射。（注意横坐标是对数形式，白矮星的辐射在紫外光、蓝光区，而岩石盘的辐射在红外、微波区）
White dwarfs are the remnants of relatively low-mass stars that have passed through their red giant stage. A white dwarf may be the size of the Earth, but contain the same mass as the Sun. This star remnant is so dense, in fact, that one teaspoon of white dwarf material wouldweigh several tons. Over 90% of all stars -- including our Sun -- will end their lives as white dwarfs.
白矮星是相对低质量恒星在经历了红巨星阶段后的归宿。白矮星可能只有地球大小，但包含的质量可能与太阳相当。事实上，白矮星的物质非常致密，1茶匙物质就有数吨重。包括我们太阳在内，90%以上的恒星的生命归宿都是白矮星。

About the Object (1)
Object name:	GD 16
Object type:	White Dwarf
Position (J2000):	RA: 01h 48m 56.80s  Dec: 19° 2' 27.66"
About the Data
Spitzer Data
Image Credit:	NASA / JPL-Caltech / University of Leicester
Instrument:	IRAC + MIPS
Release Date:	2009/04/20

上面图表的翻译，星图坐标位置从略。

Object name:GD 16
对象名称：GD 16
Object type:White Dwarf
对象类型：白矮星

Image Credit:NASA / JPL-Caltech / University of Leicester
图像版权：美国航空航天局、加州理工学院喷气推进实验室、（英国）莱斯特大学
Instrument:        IRAC + MIPS
探测仪器：斯皮策卫星的红外阵列相机和多频带成像光度计
Release Date:        2009/04/20
报告发表时间：2009.04.20

http://gallery.spitzer.caltech.edu/Imagegallery/image.php?image_name=ssc2009-01b

Asteroid 'Bites the Dust' Around Dead Star
围绕死亡恒星的小行星“微尘”

                               
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NASA's Spitzer Space Telescope set its infrared eyes upon the dusty remains of shredded asteroids around several dead stars. This artist's concept illustrates one such dead star, or "white dwarf," surrounded by the bits and pieces of a disintegrating asteroid. These observations help astronomers better understand what rocky planets are made of around other stars.
斯皮策空间望远镜把它的红外眼睛瞄向某些死亡恒星周围、由小行星残留碎片组成的尘埃带上。本艺术概念图就描绘了一个这样的恒星——“白矮星”，它身旁围绕的是小行星分裂后的残片与微尘。这些观测有助于天文学家更好的了解在其他恒星周围岩质行星的构成。
Asteroids are leftover scraps of planetary material. They form early on in a star's history when planets are forming out of collisions between rocky bodies. When a star like our sun dies, shrinking down to a skeleton of its former self called a white dwarf, its asteroids get jostled about. If one of these asteroids gets too close to the white dwarf, the white dwarf's gravity will chew the asteroid up, leaving a cloud of dust.
小行星是行星物质的残余废坯。小行星形成于恒星早期演化阶段，石质星子通过碰撞逐步长大。当类似太阳的恒星死亡时，它自身坍缩为白矮星，而它的行星们将互相乱撞。如果某个小行星离白矮星太近，它就会被撕碎而剩下一片尘埃云。
Spitzer's infrared detectors can see these dusty clouds and their various constituents. So far, the telescope has identified silicate minerals in the clouds polluting eight white dwarfs. Because silicates are common in our Earth's crust, the results suggest that planets similar to ours might be common around other stars.
斯皮策的红外望远镜能够探测到这些尘埃云并测出各种组分。迄今为止，已经在8个白矮星附近的尘埃云中检测到硅酸盐物质。因为硅Si是我们地壳的常见组分（丰度仅次于氧O），这个观测结果意味着在其他恒星周围，类地行星是普遍现象。

本文完成。
按我的理解，即使像太阳这样的恒星变成红巨星，由于其外层大气非常稀薄（大家想想彗尾的密度），所以它能膨胀到火星轨道，但对地球运行产生的影响很小。当然，地球轨道会极缓慢的靠近太阳，但等到数亿年后太阳变成白矮星时，地球轨道最多到达金星位置。所以我不能理解文章中所谓行星乱撞的说法。当然，水星由于太靠近太阳，极可能会在红巨星阶段坠入太阳而破碎。