本帖最后由 人与自然 于 2013-1-3 23:56 编辑
来源：英国每日邮报http://www.dailymail.co.uk/sciencetech/article-2256178/The-astonishing-gas-guzzling-moment-giant-planets-born.html
The birth of two giant planets guzzling gas as they orbit their parent star has been observed by scientists for the first time.
Seen by Earth's largest radio telescope, vast streams of gas flowing through a gap in a disc of material around a young star seem to support theories of how the planets grow.
The Atacama Large Millimeter / submillimeter Array (ALMA) in Chile's Atacama desert reaches farther beyond the skies than any other radio telescope.
翻译兼编者按（国内首发，意义重大，原创翻译，建议加精，呵呵）：
阿塔卡玛毫米波大天线阵(Atacama Large Millimeter/submillimeter Array,缩写为ALMA)，座落在智利阿塔卡玛海拔5000米高的查南托高原上。ALMA由66面高分辨率天线组成，包括主阵列上的50个12米天线，以及另外两阵列上的4个12米天线和12个7米天线。ALMA观测波长从9.6毫米到0.3毫米，最长基线可达16千米，这使ALMA有非常好的空间分辨率，将是哈勃空间望远镜的10倍，所成图像的清晰度可与VLT干涉阵相媲美。
ALMA本次观测到的两颗年幼行星吞噬母体恒星周边气体的影像，是人类天文史上首次发现。我认为，这两颗年幼恒星吞噬母体恒星周边气体的图像，将成为2013年度的最重大天文发现之一，毕竟过去人们只知道恒星吞噬行星，却没有观测到行星吸取恒星系统物质。年幼行星不断从母体恒星周边的吸取气体壮大自己，仿佛如同人类婴儿吮吸母亲的乳汁，难道恒星系统本身就是一个生命的奇迹？
An artist's impression of the disc of gas and cosmic dust around the young star HD 142527. Scientists have made the first direct observations of these streams 艺术想象图：气体和尘埃围绕着年轻的恒星HD 142527旋转，科学家们已经观测到这中气流现象。
Researchers studied a young star known as HD 142527 which lies over 450 light-years from Earth.
An international team of astronomers studied a young star known as HD 142527 which lies over 450 light-years from Earth.
It is surrounded by a disc of gas and cosmic dust - the remains of the cloud from which the star formed.
The dusty disc is divided into an inner and an outer part by a gap believed to have been carved by newly forming gas giant planets clearing out their orbits as they circle the star.
The inner disc reaches from the star out to the equivalent of the orbit of Saturn in the Solar System while the outer one begins about 14 times further out.
According to theory, the giant planets grow by capturing gas from the outer disc, in streams that form bridges across the gap in the disc.
Dr Simon Casassus, of Chile University in Santiago, said: 'Astronomers have been predicting these streams must exist but this is the first time we've been able to see them directly.
'Thanks to the new ALMA telescope we've been able to get direct observations to illuminate current theories of how planets are formed.'
The researchers used ALMA to look at the gas and cosmic dust around the star - seeing finer details, and closer to the star, than could be seen with previous such telescopes.
ALMA's observations, at submillimetre wavelengths, are also impervious to the glare from the star that affects infrared or visible-light telescopes.
The gap in the dusty disc was already known, but they also discovered diffuse gas remaining in the gap, and two denser streams of gas flowing from the outer disc, across the gap, to the inner disc.
Researcher Dr Sebastian Perez, also of Chile University, said: "We think there is a giant planet hidden within and causing each of these streams.
"The planets grow by capturing some of the gas from the outer disc but they are really messy eaters. The rest of it overshoots and feeds into the inner disc around the star."
科学家们研究了距离地球约450光年之外的一颗年轻恒星HD 142527 ，恒星形成初期留下的物质演变成为围绕恒星旋转的气体和尘埃盘。
尘埃盘进一步被分为内盘和外盘，内外盘之间是气体盘，而这些气体在旋转过程中形成了巨大行星。
按照理论，巨大行星不断捕食外盘的气体，形成一个气体桥，《自然》杂志最新的理论研究就是希望如此，即巨大行星形成过程中，不断从外盘中吸取气体。
圣地亚哥的智利大学博士的 Simon Casassus说，天文学家们早就从理论上认为这种气流桥存在，但是从未观测到，因此这次能观测到行星吞噬母体恒星周边气体形成的气流桥，科学价值极大。
由于有ALMA的强大帮助，天文学家们有能力观测到支持行星形成的理论。ALMA使得天文学家们能更接近，更深入细致地观测恒星及周边气体分布情况，而以前的观测设施是难以做到的。
划分尘埃盘内外的沟状空间（gap，本文姑且翻译为“天沟”），是天文学家们早就知道的，天文学家们也发现，沟内弥漫着气体，以及两个从外盘跨越天沟进入的稠密的气流桥，并达到内盘。
智利大学的Sebastian Perez博士说，“我们认为，有一个巨大的行星分别隐藏在两个气流桥的末端，就是行星的存在，才形成了这两个气流”， “行星成长过程中，不断捕食外盘气体，它们真是饥不择食，吃太多了，吃不完的气体就会进入恒星周边的内盘。”
,
Artist's conception of HD142527 system, where Gas streamers cross a gap in a protoplanetary disk 艺术想象图： HD142527 恒星系统跨越了尘埃盘的气流桥，可见两个巨大行星正是这种气流桥形成的根本原因
The observations answer another question about the disc around HD 142527.
As the central star is still forming, by capturing material from the inner disc, the inner disc would have already been devoured, if it was not somehow topped up.
The team found that the rate at which leftover gas streams onto the inner disc is just right to keep the inner disc replenished, and to feed the growing star.
Another first is the detection of the diffuse gas in the gap.
Dr Gerrit van der Plas, another team member at Chile University, said: 'Astronomers have been looking for this gas for a long time but so far we only had indirect evidence for it.
'Now, with ALMA, we can see it directly.'
This residual gas is more evidence that the streams are caused by giant planets, rather than even larger objects such as a companion star.
Drsaid: 'A second star would have cleared out the gap more, leaving no residual gas.
'By studying the amount of gas left, we may be able to pin down the masses of the objects doing the clearing.'
天文观测者们也回答了关于恒星系统HD 142527的几个问题
一是由于中央的恒星仍处于发展中，仍然要捕食内盘的物质，内盘是否已经被恒星吞噬完毕？
研究团队发现，被恒星”吃“（注：本文的翻译采用拟人方式，有助于大家理解）完气体的内盘，可以很好的得到从外盘流进来的气体补充，因此恒星可以源源不断地得到“营养供给”。
二是如何观测天沟中的弥漫气体？
智利大学的Gerrit van der Plas博士说，“多年来天文学家们一直在寻找天沟中气体，但是仅仅是间接证实其存在，现在有ALMA的帮助，我们可以直接观测到这些气体”
残留的气体充分证明了气流桥是由巨大行星引起，而非更大的星体如恒星伴星引起。
Perez 博士继续说，“通过研究剩余气体的多少，我们能够确定清理这些气体的主体（恒星）的质量”
A 28-wheeled transporter picks up a giant telescope antenna at the ALMA (Atacama Large Millimetre Array) base station, Atacama Desert, Chile, where the latest measurements were taken ALMA基地情况，这个位于智利的天文基地刚刚启用。
Dr Casassus explains although the team did not detect the planets directly, he is not surprised.
He said: 'We searched for the planets themselves with state-of-the-art infrared instruments on other telescopes.
'However, we expect these forming planets are still deeply embedded in the streams of gas, which are almost opaque.
'Therefore, there may be little chance of spotting the planets directly.'
The astronomers aim to find out more about the suspected planets by studying the gas streams as well as the diffuse gas.
The ALMA telescope is still under construction, and has not yet reached its full capabilities.
When it is complete, its vision will be even sharper, and new observations of the streams may allow the team to determine properties of the planets, including their masses.
Casassus 博士解释说，他对观测团队并未直接观测到行星并不吃惊，他说，“我们在其他望远镜上使用了最新的红外仪器装备来搜寻行星，可是，我们希望这些发育中的行星被气流仅仅包裹着，而这些气流是模糊不透明的，因此，直接发现这些行星的几率仍然很小”。
天文学家们研究弥漫气体和气流的目标，仍然是发现这些假设中存在的行星。
ALMA天文望远镜基地尚未全部完工，仍然还没有充分发挥出其力量。一旦建成，望远镜的“视力”就会更加犀利，就能帮助天文学家们更深入、更细致、更清晰研究气流和弥漫气体，进而发现行星并界定行星的性质。
Read more: http://www.dailymail.co.uk/sciencetech/article-2256178/The-astonishing-gas-guzzling-moment-giant-planets-born.html#ixzz2GvH1byvi
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