NASA昨发现Kepler-20e 天文学上重要里程碑
本帖最后由 q零度星系 于 2011-12-21 22:09 编辑http://www.cnbeta.com/articles/166482.htm
美国太空总署(NASA)自本月初发现凯普勒22b行星(Kepler-22b)后又传捷报，昨(20)日英国科学杂志《NATURE》公布消息，在太阳系外发现两颗约地球一般大小的行星，分别命名为凯普勒20e(Kepler-20e)和凯普勒20f(Kepler-20f)，成为天文学上一座重要的里程碑。
凯普勒20e的直径为11,000公里，约为地球的0.87倍，比金星略小；凯普勒20f的直径则为13,190公里，约为地球的1.03倍。两者皆位于距离地球约950光年的凯普勒20星系(Kepler-20 )中。
凯普勒20星系为一类似太阳系的恒星系，除了本次发现的2颗行星外，还包含另外3颗行星。NASA推测此2行星皆为岩石所组成，但因距离恒星较近，地表温度高，无法存在液态水，被认为不适合生命居住。
NASA凯普勒任务 (Kepler mission)的首要目标为在适居带内，找到类似地球的行星，自任务开始总共发现了2300个以上的天体，其中有48个推断可能存在有生命不可或缺的物质「水」。
本次所发现的两颗行星，为凯普勒任务迄今发现在类太阳系行星系中的最小行星，也是与地球大小最为接近的行星，虽非位于适居带内，但两者都为凯普勒任务建立了新的里程碑。
▼凯普勒20e和凯普勒20f与地球、金星的大小对照图。
〔图／翻摄自NASA〕
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Artist's Concept of Kepler-20eNASA's Kepler mission has discovered the first Earth-size planets orbiting a sun-like star outside our solar system. The planets, called Kepler-20e and Kepler-20f, are too close to their star to be in the so-called habitable zone where liquid water could exist on a planet's surface, but they are the smallest exoplanets ever confirmed around a star like our sun.
Kepler-20e is the first planet smaller than the Earth discovered to orbit a star other than the sun. A year on Kepler-20e only lasts 6 days, as it is much closer to its host star than the Earth is to the sun. The temperature at the surface of the planet, around 1400 degrees Fahrenheit, is much to hot to support life, as we know it.
Kepler-20e is likely to be entirely rocky and without an atmosphere. The planet is tidally locked, always showing the same side to its host star, as the moon to the Earth, and could have large temperature differences between its permanent night and day sides.
Astronomers think that the planet is likely to be geologically active, due to its own formation process and the strong gravitational interactions with its host star. In this artistic depiction, the planet is represented with active volcanoes on both the night and day sides.
For more information about the Kepler mission and to view the digital press kit, visit: http://www.nasa.gov/kepler
Image credit: NASA/Ames/JPL-Caltech
NASA Discovers First Earth-size Planets Beyond Our Solar System
12.20.11
http://www.nasa.gov/images/content/611923main_Kepler20e_4x3_full_226-170.jpg Click image for multiple resolutions and full caption.
This artist's conception illustrates Kepler-20e. Image credit: NASA/Ames/JPL-Caltech
http://www.nasa.gov/images/content/611936main_Kepler20f_4x3_full_226-170.jpg Click image for multiple resolutions and full caption.
This artist's conception illustrates Kepler-20f. Image credit: NASA/Ames/JPL-Caltech
http://www.nasa.gov/images/content/611759main_PlanetLineup_4x3_full_226-170.jpg Click image for multiple resolutions and full caption.
This chart compares artist's concept images of the first Earth-size planets found around a sun-like star to planets in our own solar system, Earth and Venus. Image credit: NASA/Ames/JPL-Caltech
MOFFET FIELD, Calif. -- NASA's Kepler mission has discovered the first Earth-size planets orbiting a sun-like star outside our solar system. The planets, called Kepler-20e and Kepler-20f, are too close to their star to be in the so-called habitable zone where liquid water could exist on a planet's surface, but they are the smallest exoplanets ever confirmed around a star like our sun.
The discovery marks the next important milestone in the ultimate search for planets like Earth. The new planets are thought to be rocky. Kepler-20e is slightly smaller than Venus, measuring 0.87 times the radius of Earth. Kepler-20f is a bit larger than Earth, measuring 1.03 times its radius. Both planets reside in a five-planet system called Kepler-20, approximately 1,000 light-years away in the constellation Lyra.
Kepler-20e orbits its parent star every 6.1 days and Kepler-20f every 19.6 days. These short orbital periods mean very hot, inhospitable worlds. Kepler-20f, at 800 degrees Fahrenheit, is similar to an average day on the planet Mercury. The surface temperature of Kepler-20e, at more than 1,400 degrees Fahrenheit, would melt glass.
“The primary goal of the Kepler mission is to find Earth-sized planets in the habitable zone," said Francois Fressin of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., lead author of a new study published in the journal Nature. "This discovery demonstrates for the first time that Earth-size planets exist around other stars, and that we are able to detect them.”
The Kepler-20 system includes three other planets that are larger than Earth but smaller than Neptune. Kepler-20b, the closest planet, Kepler-20c, the third planet, and Kepler-20d, the fifth planet, orbit their star every 3.7, 10.9 and 77.6 days. All five planets have orbits lying roughly within Mercury's orbit in our solar system. The host star belongs to the same G-type class as our sun, although it is slightly smaller and cooler.
The system has an unexpected arrangement. In our solar system, small, rocky worlds orbit close to the sun and large, gaseous worlds orbit farther out. In comparison, the planets of Kepler-20 are organized in alternating size: large, small, large, small and large.
"The Kepler data are showing us some planetary systems have arrangements of planets very different from that seen in our solar system," said Jack Lissauer, planetary scientist and Kepler science team member at NASA's Ames Research Center in Moffett Field, Calif. "The analysis of Kepler data continue to reveal new insights about the diversity of planets and planetary systems within our galaxy."
Scientists are not certain how the system evolved but they do not think the planets formed in their existing locations. They theorize the planets formed farther from their star and then migrated inward, likely through interactions with the disk of material from which they originated. This allowed the worlds to maintain their regular spacing despite alternating sizes.
The Kepler space telescope detects planets and planet candidates by measuring dips in the brightness of more than 150,000 stars to search for planets crossing in front, or transiting, their stars. The Kepler science team requires at least three transits to verify a signal as a planet.
The Kepler science team uses ground-based telescopes and the Spitzer Space Telescope to review observations on planet candidates the spacecraft finds. The star field Kepler observes in the constellations Cygnus and Lyra can be seen only from ground-based observatories in spring through early fall. The data from these other observations help determine which candidates can be validated as planets.
To validate Kepler-20e and Kepler-20f, astronomers used a computer program called Blender, which runs simulations to help rule out other astrophysical phenomena masquerading as a planet.
On Dec. 5 the team announced the discovery of Kepler-22b in the habitable zone of its parent star. It is likely to be too large to have a rocky surface. While Kepler-20e and Kepler-20f are Earth-size, they are too close to their parent star to have liquid water on the surface.
"In the cosmic game of hide and seek, finding planets with just the right size and just the right temperature seems only a matter of time," said Natalie Batalha, Kepler deputy science team lead and professor of astronomy and physics at San Jose State University. "We are on the edge of our seats knowing that Kepler's most anticipated discoveries are still to come."
NASA's Ames Research Center in Moffett Field, Calif., manages Kepler's ground system development, mission operations and science data analysis. JPL managed the Kepler mission's development.
Ball Aerospace and Technologies Corp. in Boulder, Colo., developed the Kepler flight system and supports mission operations with the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder.
The Space Telescope Science Institute in Baltimore archives, hosts and distributes Kepler science data. Kepler is NASA's 10th Discovery Mission and is funded by NASA's Science Mission Directorate at the agency's headquarters in Washington.
For more information about the Kepler mission and to view the digital press kit, visit: http://www.nasa.gov/kepler
This artist's animation flies through the Kepler-20 star system, where NASA's Kepler mission discovered the first Earth-size planets around a star beyond our own. Animation credit: NASA/Ames/JPL-Caltech
我回家居找找数据，争取把开普勤第二季公布的1235颗候选者中24个小于地球的详细信息发上来。 地球的直径什么时候有1万多公里了？ Fidodido 发表于 2011-12-21 13:57 static/image/common/back.gif
地球的直径什么时候有1万多公里了？
地球的半径约6500KM.
记混了吧，朋友。
czman 发表于 2011-12-21 14:30 static/image/common/back.gif
地球的半径约6500KM.
记混了吧，朋友。
看LZ的正文。看LZ的正文。看LZ的正文。 Fidodido 发表于 2011-12-21 14:48 static/image/common/back.gif
看LZ的正文。看LZ的正文。看LZ的正文。
直径和半径能分开吗
仔细看看你发的标题，有什么问题没有？ 本帖最后由 sonic5188 于 2011-12-21 19:35 编辑
找了一下，附件是开普勒第二季(1235候选者)数据中小于地球半径1.2倍的行星数据！
其中一颗行星KOI 326.01 表面温度60度，0.9倍地球半径，比较有意思，估计和地球最像了。
可惜距离恒星0.05AU，红矮星辐射不稳定，该星离恒星距离只有10个恒星直径那么长！
可见我们想找真正的地球，难上加难！大小，位置，母恒星甚至对邻居都有苛刻的要求。
不过假以时日，我们也许会在数百万颗系外行星中找到一个和地球几乎一样的行星，
但是这颗行星的历史和地球会相似吗？大家应该知道地球之所以变成现在的样子，
基本条件是一个基础，各种地球历史事件是另一个基础，特别是早期事件！ 本帖最后由 sonic5188 于 2011-12-22 07:51 编辑
再按照行星表面辐射温度(与实际温度有差别，例如金星)排序，
我勉强在1235个行星候选者中找到了一个超级地球KOI 703.01，1.7倍地球半径，温度和地球类似。
大于3倍地球半径的行星肯定覆盖有浓密的大气层，接近海王星的性质，高温和风暴很难发展出高级生命。
还有两个KOI 1026.01，KOI 854.01，接近2倍地球半径如有适当的大气层，温度也可能维持在10度以上。
我选的温度范围是参照地球来设定的，地球的表面辐射温度(就是除去大气层的温室效应)应该在255K附近。
地球的平均温度是15度，288K，温室气体提高接近33度，最主要的温室气体其实是水蒸气。
那些表面辐射温度超过60度，也就是333K的行星是不考虑的，加上温室效应温度肯定过100度。
上一楼提到的KOI 326.01这个行星也在这个表的最后几行中。 xywr 发表于 2011-12-21 17:04 static/image/common/back.gif
直径和半径能分开吗
果然没看清楚。呵呵。 sonic5188 发表于 2011-12-21 18:33 static/image/common/back.gif
找了一下，附件是开普勒第二季(1235候选者)数据中小于地球半径1.2倍的行星数据！
其中一颗行星KOI 326.01...
问下何为第二季,不一共就1235个么
顺便问下，这个星系里有类木行星吗 本帖最后由 sonic5188 于 2011-12-22 10:23 编辑
gliese581 发表于 2011-12-22 09:00 http://www.astronomy.com.cn/bbs/static/image/common/back.gif
问下何为第二季,不一共就1235个么
目前我只找到第二季1235的全部数据包括宿主恒星的，谁有第四季报2326全部数据的，我拿200牧夫币买。
2326中有207颗接近地球大小的候选者(明显增加)，680个超级地球，1181个海王星，203个木星和55个超级木星。
看来开普勒发现的主力是超级地球和海王星，与之前发现的大部分是木星和超级木星有明显差异。
当然越小的行星应该越多，如果开普勒真的能延长服役到2017年，我估计发现1000颗地球大小的行星是可能的。
本帖最后由 sonic5188 于 2011-12-22 10:29 编辑
三叶观天 发表于 2011-12-22 09:37 http://www.astronomy.com.cn/bbs/static/image/common/back.gif
顺便问下，这个星系里有类木行星吗
没有，至少目前没有发现。不排除今后可能会有较长周期的行星被发现的可能。
这个系统中的直径最接近地球的Kepler-20 f 就是在后期数据中被发现的。
如果这个数据早期就被发现，也许这个系统也早就被公布了。
Kepler控制小组NASA Ames中心调大众胃口的手段实在高明，一个个公布，公布的都是有亮点的，
要不是多行星系统的，如今年初的Kepler-11六星系统，要不就是接近地球温度的，如不久前的Kepler-22b。
让媒体不断炒作，提高民众支持度，不断增加向国会要后续资金的砝码。
本帖最后由 三叶观天 于 2011-12-22 10:40 编辑
sonic5188 发表于 2011-12-22 10:21 http://www.astronomy.com.cn/bbs/static/image/common/back.gif
没有，至少目前没有发现。不排除今后可能会有较长周期的行星被发现的可能。
这个系统中的直径最接近地球 ...
还以为只有apple公司才会搞饥饿营销:P 本帖最后由 sonic5188 于 2011-12-22 11:03 编辑
三叶观天 发表于 2011-12-22 10:39 http://www.astronomy.com.cn/bbs/static/image/common/back.gif
还以为只有apple公司才会搞饥饿营销
09年3月到10年3月仅仅1年的数据，就能发现2326个候选者，如果任务时间延长到8年，数字可想而知。
到今天，Ames中心也才正式向外公布开普勒发现的33个系外行星，还有至少2000颗未正式公布。
2000颗够他们喝一壶的了 sonic5188 发表于 2011-12-22 10:21 static/image/common/back.gif
没有，至少目前没有发现。不排除今后可能会有较长周期的行星被发现的可能。
这个系统中的直径最接近地球 ...
还是需要验证的吧,比如相当有趣的KOI730就没公布 sonic5188 简直是个超级行星迷！:D
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