ESO091216：天文学家发现另一世界
本帖最后由 其祥 于 2010-1-3 12:12 编辑http://www.eso.org/public/news/eso0950/
ESO0950 - News Release，16 December 2009
ESO0950，新闻发布，2009年12月16日
Astronomers Find World with Thick, Inhospitable Atmosphere and an Icy Heart
天文学家发现含有浓厚、不宜居住大气层与冰体核心的另一世界
Astronomers have discovered the second super-Earth exoplanet for which they have determined the mass and radius, giving vital clues about its structure. It is also the first super-Earth where an atmosphere has been found. The exoplanet, orbiting a small star only 40 light-years away from us, opens up dramatic new perspectives in the quest for habitable worlds. The planet, GJ1214b, has a mass about six times that of Earth and its interior is likely to be mostly made of water ice. Its surface appears to be fairly hot and the planet is surrounded by a thick atmosphere, which makes it inhospitable for life as we know it on Earth.
天文学家已经发现太阳系外第二个“超级地球”，并已确定其质量和半径，而且也给出了有关其结构的最新情况。同时它也是被发现的第一颗含有大气层的“超级地球”。这颗系外行星（GJ1214b）距离地球约40光年，重新激起了人类探索宜居世界的热潮。它的质量约地球的6倍，而且其内部主要由水、冰构成。但是这颗行星的表面似乎温度很高，被浓厚的大气层所覆盖，按照我们对地球上生命的认识，这使得它不太适合生命居住。
本帖最后由 其祥 于 2010-1-3 03:20 编辑
In this week’s issue of Nature, astronomers announce the discovery of a planet around the nearby, low-mass star GJ1214 . It is the second time a transiting super-Earth has been detected, after the recent discovery of the planet Corot-7b . A transit occurs when the planet's orbit is aligned so that we see it crossing the face of its parent star.The newly discovered planet has a mass about six times that of our terrestrial home and 2.7 times its radius, falling in size between the Earth and the ice giants of the Solar System, Uranus and Neptune.
在这周的《自然》杂志上所发表的论文中，天文学家宣布发现了这颗绕转小质量恒星--GJ1214的行星。这是继最近发现的系外行星Corot-7b之后，通过掩星（其祥注：掩星是一种天文现象，指一个天体在另外一个天体与观测者之间通过时所产生的遮蔽现象）探测到的第二颗“超级地球”。最新发现的这颗系外行星质量约为地球的6倍，半径约为地球的2.7倍。大小介于地球与太阳系的冰巨人（天王星、海王星）之间。
Although the mass of GJ1214b is similar to that of Corot-7b, its radius is much larger, suggesting that the composition of the two planets must be quite different. While Corot-7b probably has a rocky core and may be covered with lava, astronomers believe that three quarters of GJ1214b is composed of water ice, the rest being made of silicon and iron.
尽管GJ1214b的质量与Corot-7b相近，但是它的半径要大的多，这也表明组构成这两颗系外行星的物质成分会有很大不同。Corot-7b的表面很可能是被岩浆覆盖的岩石地表，而天文学家们坚信GJ1214b上月3/4的地表被水冰覆盖，剩下的很有可能由硅和铁构成。
GJ1214b orbits its star once every 38 hours at a distance of only two million kilometres — 70 times closer to its star than the Earth is to the Sun. “Being so close to its host star, the planet must have a surface temperature of about 200 degrees Celsius, too hot for water to be liquid,” says David Charbonneau, lead author of the paper reporting the discovery.
相比于地球绕转太阳的轨道，GJ1214b的轨道半径要缩短了70倍，仅仅只距离它的“太阳”约两百万公里，绕转周期约为38小时。据论文的第一作者David Charbonneau说，因为它距离主星这样近，所以其表面温度约为200摄氏度，如此，水不会以液态形式存在。 When the astronomers compared the measured radius of GJ1214b with theoretical models of planets, they found that the observed radius exceeds the models’ predictions: there is something more than the planet’s solid surface blocking the star’s light — a surrounding atmosphere, 200 km thick.“This atmosphere is much thicker than that of the Earth, so the high pressure and absence of light would rule out life as we know it,” says Charbonneau, “but these conditions are still very interesting, as they could allow for some complex chemistry to take place.”
当天文学家们将GJ1214b与行星的理论模型相比对时，他们发现所测量的行星半径要比理论上大一些，这也就是说，在这颗行星的固体地表之上，被200km厚的大气层包裹。Charbonneau 还说，“它的大气层厚度要比地球的厚得多，以至于地表压强很大，光也无法透过大气层，如我们所知，这样不太适合生命居住，但是有意思的是，这样的条件会导致发生一些复杂的化学反应。
“Because the planet is too hot to have kept an atmosphere for long, GJ1214b represents the first opportunity to study a newly formed atmosphere enshrouding a world orbiting another star,” adds team member Xavier Bonfils. “Because the planet is so close to us, it will be possible to study its atmosphere even with current facilities.”
团队成员Xavier Bonfils补充道，“由于这颗行星的表面温度如此之高，故其大气层不会长久存在，GJ1214b就为我们提供了第一个研究绕主星转动的行星的大气层是如何形成的机会。又因为这颗行星距离我们如此的近，所以，即使利用我们当前的设备也很有可能研究它的大气层。” 本帖最后由 其祥 于 2010-1-3 10:20 编辑
The planet was first discovered as a transiting object within the MEarth project, which follows about 2000 low-mass stars to look for transits by exoplanets . To confirm the planetary nature of GJ1214b and to obtain its mass (using the so-called Doppler method), the astronomers needed the full precision of the HARPS spectrograph, attached to ESO’s 3.6-metre telescope at La Silla. An instrument with unrivalled stability and great precision, HARPS is the world’s most successful hunter for small exoplanets.
在跟踪观测大约2000颗低质量恒星的MEarth工程项目中，这颗行星当作为掩星物体时第一次被发现。为了确证GJ1214b的自然环境，以及得到其质量大小（应用所谓的多普勒视向法），天文学家们应用了固定在ESO拉西拉天文台的3.6m望远镜上的高精度视向速度行星搜索器（HARPS---High Accuracy Radial Velocity Planet Searcher），它是世界上最著名的“行星猎手”，拥有着无与伦比的稳定性和高精度。
“This is the second super-Earth exoplanet for which the mass and radius could be obtained, allowing us to determine the density and to infer the inner structure,” adds co-author Stephane Udry. “In both cases, data from HARPS was essential to characterise the planet.”
论文的第二作者Stephane Udry补充说，“这是截至目前为止我们发现的第二颗可以被探测出质量以及半径的“超级地球”，得知这些参数，我们可以分析出这颗系外行星的密度，也可以推断出其内部结构。无论怎么说，HARPS对确定这颗行星的特征都起了至关重要的作用”。
“The differences in composition between these two planets are relevant to the quest for habitable worlds,” concludes Charbonneau. If super-Earth planets in general are surrounded by an atmosphere similar to that of GJ1214b, they may well be inhospitable to the development of life as we know it on our own planet.
Charbonneau最后做结论说，“这两颗行星之间的差别和我们寻找宜居世界都是相关的”，如果“超级地球”大体上都被类似于GJ1214b的大气层所覆盖，据我们对地球上生命演化的理解，它们很有可能都不适合生命存在。 本帖最后由 其祥 于 2010-1-3 10:53 编辑
Notes
注释
A super-Earth is defined as a planet between one and ten times the mass of the Earth. An exoplanet is a planet orbiting a star other than the Sun.
【1】“超级地球”：介乎地球与10倍地球质量之间的行星。系外行星就是一个绕转恒星（太阳除外）运动的行星。
The star GJ1214 is five times smaller than our Sun and intrinsically three hundred times less bright.
【2】恒星GJ1214，比我们的太阳小五倍，而且本质上讲，亮度也暗三百倍。
Corot-7b is the smallest and fastest-orbiting exoplanet known and has a density quite similar to the Earth's, suggesting a solid, rocky world. Discovered by the CoRoT satellite as a transiting object, its true nature was revealed by HARPS (ESO 33/09).
【3】Corot-7b是已知的质量最小，而且绕转轨道最远的系外行星，并且它的密度与地球极其相似，也就是说，它是一个固体的由岩石构成的星球。它掩星时由CoRot卫星发现。其自然参数最终由HARPS确定。
The MEarth project uses an armada of eight small telescopes each with a diameter of 40 cm, located on top of Mount Hopkins, Arizona, USA. MEarth looks for stars that change brightness. The goal is to find a planet that crosses in front of, or transits, its star. During such a mini-eclipse, the planet blocks a small portion of the star’s light, making it dimmer. NASA’s Kepler mission also uses transits to look for Earth-sized planets orbiting Sun-like stars. However, such systems dim by only one part in ten thousand. The higher precision required to detect the drop means that such worlds can only be found from space. In contrast, a super-Earth transiting a small, red dwarf star yields a greater proportional decrease in brightness and a stronger signal that is detectable from the ground.
【4】MEarth工程是位于美国亚利桑那州霍普金斯山上，由8架直径为40cm的小型望远镜组成的阵列。它专门用来寻找亮度发生变化的恒星，其目的就是通过掩星寻找系外行星。在掩星过程发生时，恒星亮度存在微小的变化，会变暗一些。NASA的开普勒任务也是用来寻找围绕“类太阳恒星”运动的“系外类地球行星”。然而，这样的“类太阳系”发生掩星时，其亮度仅仅降低1/10000。这样一来就需要更高精度的探测器来寻找太空中的“其他世界”。相比之下，当“超级地球”绕转一个小的红矮星运动时，这颗恒星的亮度会发生很大范围的降低，如此，在地球上更容易被探测到。 本帖最后由 其祥 于 2010-1-3 11:01 编辑
相关论文链接
This research was presented in a paper appearing this week in Nature (“A Super-Earth Transiting a Nearby Low-Mass Star”, by David Charbonneau et al.).
这项研究由David Charbonneau等人以论文的形式发表在这周的《自然》杂志上，名为《一个紧邻低质量恒星的“超级地球”》
论文下载链接
• Science paper
• More info: Exoplanet Media Kit
我已经下载过，大家若有兴趣可以在此下载：
Nature论文：
本帖最后由 其祥 于 2010-1-3 11:06 编辑
Contacts
联系方式
Stéphane Udry
Geneva University, Switzerland
瑞士日内瓦大学
Geneva, Switzerland
日内瓦，瑞士
Tel: +41 22 379 2467
Email: stephane.udry@unige.ch
Xavier Bonfils
Université Joseph Fourier - Grenoble 1 / CNRS, Laboratoire d'Astrophysique de Grenoble (LAOG), France
France
Tel: +33 47 65 14 215
Email: xavier.bonfils@obs.ujf-grenoble.fr
David Charbonneau
Harvard-Smithsonian Center for Astrophysics
哈佛史密森天体研究中心
Cambridge, USA
剑桥，美国（剑桥不是英国的城市吗？O(∩_∩)O）
Tel: +1 617 496 6515
Email: dcharbon@cfa.harvard.edu 本帖最后由 其祥 于 2010-1-3 11:27 编辑
http://www.eso.org/public/images/eso0950a/
GJ1214b (Artist’s impression)
GJ1214b(艺术家想象图)
This artist’s impression shows how the newly discovered super-Earth surrounding the nearby star GJ1214 may look. Discovered by the MEarth project and investigated further by the HARPS spectrograph on ESO’s 3.6-metre telescope at La Silla, GJ1214b is the second super-Earth exoplanet for which astronomers have determined the mass and radius, giving vital clues about its structure. It is also the first super-Earth around which an atmosphere has been found. The exoplanet, orbiting a small star only 40 light-years away from us, thus opens dramatic new perspectives in the quest for habitable worlds. The planet, GJ1214b, has a mass about six times that of Earth and its interior is likely mostly made of water ice. It appears to be rather hot and surrounded by a thick atmosphere, which makes it inhospitable for life as we know it on Earth.
这是一张展示最近发现的绕转GJ1214运动的艺术幻想图。同时它也是被发现的第一颗含有大气层的“超级地球”。由MEarth项目发现，通过固定在ESO拉西拉天文台的3.6m望远镜上的高精度视向速度行星搜索器HARPS进行了相关探测，并已确定其质量和半径，而且也给出了有关其结构的最新情况。这颗系外行星（GJ1214b）距离地球约40光年，重新激起了人类探索宜居世界的热潮。它的质量约地球的6倍，而且其表面很有可能大部分由水冰构成。但是这颗行星的表面似乎温度很高，被浓厚的大气层所覆盖，按照我们对地球上生命的认识，这使得它不太适合生命居住。
Credit:
ESO/L. Calçada
版权：ESO/L. Calçada
全景原始图下载链接： TIF格式， 18.85M
http://www.eso.org/public/archives/images/original/eso0950a.tif
JEPG大图下载链接，4.3M
http://www.eso.org/public/archives/images/large/eso0950a.jpg 本帖最后由 其祥 于 2010-1-3 11:43 编辑
http://www.eso.org/public/images/eso0950b/
The star GJ1214
恒星GJ1214
GJ1214 is a star five times smaller than our Sun and three hundred times less bright. Located only 40 light-years away from us, it is found to be surrounded by a super-Earth planet whose interior is likely mostly made of water ice. The planet appears to be rather hot and surrounded by a thick atmosphere, which makes it inhospitable for life as we know it on Earth.
恒星GJ1214，是我们的太阳的五分之一大小，而且本质上讲，亮度也暗三百倍，距离地球约40光年，被一颗表面很有可能大部分由水冰构成的行星绕转。但是这颗行星的表面似乎温度很高，被浓厚的大气层所覆盖，按照我们对地球上生命的认识，这使得它不太适合生命居住。
This image is based on data obtained through 2 different filters (blue and red), which were taken 7 years apart. Because the star is very close to the Earth, it has a large apparent motion on the sky, and so has moved in between the 7 years. This is why the star appears as a double coloured object in this image.
这张图片的数据获得是通过两个不同的滤光片（蓝色和红色），间隔七年进行拍摄。因为这颗恒星距离地球很近，所以它在这七年中天空中有明显的移动。这也是为何这颗恒星在图片中看起来有双色的原因。
Credit:
ESO/Digitized Sky Survey 2
版权：ESO/数字巡天2
原始全景图下载链接：TIF文件 221.67M
http://www.eso.org/public/archives/images/original/eso0950b.tif
JEPG格式大图下载链接：117.5M
http://www.eso.org/public/archives/images/large/eso0950b.jpg 本帖最后由 其祥 于 2010-1-3 11:47 编辑
视频链接：
GJ1214b (Artist’s impression)
GJ1214b（艺术家幻想图）
http://www.eso.org/public/videos/eso0950a/
Zoom in on the star GJ1214 (annotated)
恒星GJ1214的放大图（有注解）
http://www.eso.org/public/videos/eso0950b/
GJ1214 is a star five times smaller than our Sun and three hundred times less bright. Located only 40 light-years away from us, it is found to be surrounded by a super-Earth planet whose interior is likely mostly made of water ice. The planet appears to be rather hot and surrounded by a thick atmosphere, which makes it inhospitable for life as we know it on Earth.
恒星GJ1214，是我们的太阳的五分之一大小，而且本质上讲，亮度也暗三百倍，距离地球约40光年，被一颗表面很有可能大部分由水冰构成的行星绕转。但是这颗行星的表面似乎温度很高，被浓厚的大气层所覆盖，按照我们对地球上生命的认识，这使得它不太适合生命居住。
Zoom in on the star GJ1214
http://www.eso.org/public/videos/eso0950c/
Credit:
版权
ESO/Digitized Sky Survey 2
ESO/数字巡天2 先睡个觉，起来再翻译吧。呵呵，愿大家have a good night。 :handshake:handshake yct54.gif,,,
,,, GJ1214在哪个星座方向？我在Celestia软件上也没找到它。 本帖最后由 zhangyf1997 于 2010-1-3 21:13 编辑
GJ1214b离主星才200万公里！这比水星还要近呢。这颗行星上一定全是片沸腾的火海。 GJ1214在哪个星座方向？我在Celestia软件上也没找到它。
zhangyf1997 发表于 2010-1-3 09:48 http://www.astronomy.com.cn/bbs/images/common/back.gif
回zhangyf1997同好，其位置你可以参照10楼的“Zoom in on the star GJ1214 (annotated) http://www.eso.org/public/videos/eso0950b/”这个链接看一下，是数字巡天的结果。 GJ1214离主星才200万公里！这比水星还要近呢。这颗行星上一定全是片沸腾的火海。
zhangyf1997 发表于 2010-1-3 09:50 http://www.astronomy.com.cn/bbs/images/common/back.gif
呵呵，这个好像不是，文章里说其温度的确很高，但是它具有浓厚的大气层，以至于光线无法穿透，所以不一定全是片沸腾的火海。 发完这个帖子，又遐想了一次系外智慧生命。。。 本帖最后由 gohomeman1 于 2010-1-3 13:10 编辑
ESO在科学背景方面确实比不过哈勃官网，既使改版后，仍旧不提供天球坐标。
另外请大家注意，虽然距离很近，但是中心恒星很暗弱，其直径为太阳的20%（PDF中貌似说0.18倍），辐射光度只有太阳的1/300。HARPS对于近距离掩星观测效果很好，更何况这个卫星其实不小，掩星时光度减弱了1.3%呢。具体等其祥补充贴图吧。
贴一个图，让大家对已经发现的几个著名系外行星有所了解。可以看到，由于观测条件、仪器的限制，现在发现的绝大部分系外行星不但与我们的地球很不像，而且与主星的关系也与我们太阳系差别很大。不过，随着观测仪器的能力提高，以后应该会发现更多的类地行星。注意，图中横坐标是地球质量倍数的对数形式，右上大批的行星尚未一个个发表报告来说明。 很好的资料，需要好好的理解！
页:
[1]
2