本帖最后由 gohomeman1 于 2010-11-24 12:31 编辑
http://www.universetoday.com/2009/03/12/stars-at-milky-way-core-exhale-carbon-oxygen/
Stars at Milky Way Core 'Exhale' Carbon, Oxygen
银河系核心区的恒星“呼出”碳、氧
March 12th, 2009，Written by Anne Minard
作者安妮.Minard，写于2009.3.12
Carbon and oxygen have been spotted in the dust around stars in the center of the Milky Way galaxy, suggesting that the stars have undergone recent disruptions of some kind — and hinting at a new way that stars can send heavy elements— like oxygen, carbon, and iron — out across the universe, paving the way for life.
在银河系核心区，碳（C）和氧（O）元素被恒星抛到它周围的尘埃云中。天文学家推测它们最近经历了一系列的瓦解过程，这暗示着恒星向宇宙抛射重元素（比如C、O、Fe等）的一条新途径，为生命形成铺平道路。
Scientists have long expected to find carbon-rich stars in ourgalaxy because we know that significant quantities of carbon must be created in many such stars. But carbon had not previously shown up in the clouds of gas around these stars, said Matthew Bobrowsky, an astrophysicist at the University of Maryland and a co-author of a new study reporting the discovery.
长期以来，科学家都很期待在银河系内发现富碳恒星，因为我们知道大量的C元素是它们制造的。但是，新研究报告的联合作者、马里兰大学天体物理学家Matthew Bobrowsky 说：“以前我们并没有在这些恒星附近的气体云中发现（大量的）碳元素。”
“Based on our findings, this is because medium-sized stars rich in carbon sometimes keep that carbon hidden until very near the end of their stellar lives, releasing it only with their final ‘exhalations’,” explained Bobrowsky.
Bobrowsky继续说：“根据我们的观测，这是因为中等尺度的恒星（比如太阳——译注）持续富集C元素直到它们的生命末期，仅在它们的最后'喘息'时才释出碳。”
The new results appear in the February issue of the journal Astronomy and Astrophysics.
新研究报告发表在2009.2月的《天文学与天体物理学》期刊上。
Bobrowsky and his team, led by J. V. Perea-Calderón at the EuropeanSpace Astronomy Centre in Madrid, Spain, used the Spitzer Space Telescope to view each star and its surrounding clouds of dust and particles, called a planetary nebulae. The researchers measured the light emitted by the stars and the surrounding dust and were able to identify carbon compounds based on the wavelengths of light emitted by the stars. Looking in an area at the center of the Milky Way called the“Galactic Bulge,” the team observed 26 stars and their planetary nebulae and found 21 with carbon “signatures.”
Bobrowsky和他的团队，由位于西班牙马德里的欧洲天文学中心的J. V. Perea-Calderón牵头（关系好复杂的说——译注），使用Spitzer红外空间望远镜观测了多个带有行星状星云的恒星（这些星云由气体尘埃等组成，貌似废话）。 研究人员测量恒星和它的尘埃环的光谱，从而把碳化合物谱线从恒星的光谱线中分辨出来。在银河中心的“星系核球区”，研究人员研究了26个恒星和它们的行星状星云，发现其中的21个带有碳“签名”。
But the scientists did not just find carbon around these stars;they also found oxygen in these 21 dust clouds, revealing a surprising mixture of ingredients for space dust. They report in their paper that this is likely due to a thermal pulse where a wave of high-pressure gas mixes layers of elements like carbon and oxygen and spews them out into the surrounding cloud.
科学家不仅发现了C，他们还在21个尘埃环中都发现了O，惊讶于发现太空尘埃就像拌和的饲料一样。在报告中，他们解释说这可能是因为高压气体产生的热脉冲波把各层的C、O元素混合在一起并喷发到周围的气体云。
The finding of carbon and oxygen in the dust clouds surrounding stars suggests a recent change of chemistry in this population of stars, according to the authors.
根据作者的看法，在行星状星云中发现C、O的事实将对此类恒星的化学组成产生新的改变。
“Stars in the center of the Milky Way are old and ‘metal-rich’ with a high abundance of heavy elements,” Bobrowsky said. “They are different in chemical composition than those found in the disc, farther out from the center.”
Bobrowsky解释道：“银河中心的恒星都比较古老，是‘富金属’星，重元素丰度很高。它们与远离核心区的银盘上的恒星的化学组成很不一样。”
Studying the chemistry of the stars helps scientists learn how the matter that makes up our earth and other planets in our galaxy left its stellar birth places long ago.
研究恒星的化学组成有助于科学家了解组成我们地球和其他行星的物质，很久以前是怎样离开恒星诞生地的。
As a star burns hotter and hotter, the hydrogen gas that originally made up almost all of its mass is converted, through nuclearfusion, first to helium, and then to progressively heavier elements.The hottest region in the core fuses together the heaviest elements. And these can reach the surface of the star only when its life is almost over.
随着恒星演化，它的核心越来越热，最初几乎全部由氢（H）组成的物质将逐步聚变。通过热核反应，开始是氦（He），接着是更重的元素。恒星最热的核心区进行最重元素的融合。只有当恒星生命将结束时，重元素才能抵达恒星表面。（太阳这样的恒星最多能进行3He聚变为C的反应和C+He=O+2v（简化式）的反应，更多重元素需要大质量恒星——译注）
“The Big Bang produced only hydrogen and helium,” Bobrowsky said. “Heavier elements like carbon and oxygen only come from getting ‘cooked up’ in stars. Nuclear reactions in stars created the heavier elements found in ‘life as we know it’.”
Bobrowsky说：“宇宙大爆炸后只形成了H和He，更重的元素像C、O等只能在恒星熔炉中锻造。热核反应创造的重元素构成了'我们所知道的生命'。”（一首重金属摇滚歌曲，这是双关语——gohomeman1注）
In the last 50,000 years of their 10 billion-year lives,sun-sized stars expel carbon atoms along with hydrogen and helium to form a surrounding cloud of gas that soon disperses into space, perhaps to eventually become the stuff of new stars, solar systems, or perhaps even life on some earth-like planet. Much larger stars expel their heavier matter in massive explosions called supernovae.
在类太阳恒星100亿年生命的最后5万年期间，C和H、He等一起被恒星驱离并形成周围的气体云，然后迅速消散在宇宙空间中。这些物质可能最后形成了新的恒星、太阳系，还可能形成像我们地球这样的行星。大质量恒星（一般指10个太阳质量以上）通过巨大的超新星爆发抛射它们的重元素。
“All the heavy elements [which astronomers call ‘metals,’ and include all elements heavier than hydrogen and helium] on Earth were created by nuclear fusion reactions in previous generations of stars,”said Bobrowsky. “Those earlier stars expelled those elements into space and then our solar system formed out of that gas containing all the heavy elements that we now find in Earth and in life on Earth.”
Bobrowsky总结道：“地球上的所有重元素都是N世代以前其他恒星的热核反应产生的，早期恒星制造并抛射重元素到太空中。我们的太阳系就从包含各种重元素的气体云中形成，而今，这些重元素在地球上和我们的生命中”。（注：天文学家所说的“金属”指所有原子序数大于He的元素）
LEAD IMAGE CAPTION: Cat's Eye Nebula.
题头图片：猫眼星云 NGC 6543
Credit: NASA/JPL-Caltech/J. Hora (Harvard-SmithsonianCfA)
版权：美国宇航局（NASA），加州理工学院、喷气推进实验室（JPL），哈佛—史密松天体物理中心（CfA）J. Hora
Source: Astronomy & Astrophysics and Spitzer, via AAS
原文来源：《天文学与天体物理学》网站、斯必泽红外卫星网站、美国天文学会网站 |
置顶卡
变色卡
千斤顶
显身卡
