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NASA发现迄今最遥远星系 距地132亿光年  

2012-09-23 23:16:52|  分类: 默认分类 |  标签: |举报 |字号 订阅

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核心提示:美国航天局日前报告说,天文学家观测到迄今已知的最遥远星系,与地球相距132亿光年。这一星系体积小,结构紧凑,质量约为银河系的1%。

NASA发现迄今最遥远星系 距地132亿光年 - 常大天文社 - 常州大学天文社

In the big image at left, the many galaxies of a massive cluster called MACS J1149+2223 dominate the scene. Gravitational lensing by the giant cluster brightened the light from the newfound galaxy, known as MACS 1149-JD, some 15 times. At upper right, a partial zoom-in shows MACS 1149-JD in more detail, and a deeper zoom appears to the lower right..  

美国航天局日前报告说,天文学家观测到迄今已知的最遥远星系,与地球相距132亿光年。

据介绍,新发现的星系被称为“MACS 1149-JD”,诞生于宇宙大爆炸之后约5亿年。根据大爆炸理论,宇宙诞生于约137亿年前。由于该星系与地球之间相距约132亿光年,因此,现在探测到的光线实际上是约132亿年前发出的。

这一星系体积小,结构紧凑,质量约为银河系的1%。研究人员利用哈勃太空望远镜和斯皮策太空望远镜,在5个不同波段均观测到了来自这一星系的光,从而确认了这一遥远而古老星系的存在。此前探测到的这一“年龄段”的其他星系均是在一个波段被观测到的。

美国航天局说,这一遥远星系存在的时期对于研究宇宙“黑暗时代”具有重要意义。大爆炸后38万年至10亿年,大量氢气弥散在宇宙中,由于没有新的光源产生,宇宙是黑暗的。后来星系越来越多,“氢气雾”被它们产生的电磁辐射驱散后,宇宙才开始亮起来。对“黑暗时代”的研究是当今科学前沿课题之一。而发现和研究在“黑暗时代”诞生的恒星和星系,是揭开这一时代奥秘的关键。

本文来源:http://discovery.163.com/12/0922/08/8C0B0K3B000125LI.html?from=index

 

NASA Telescopes Spy Ultra-Distant Galaxy       09.19.12

PASADENA, Calif. -- With the combined power of NASA's Spitzer and Hubble space telescopes, as well as a cosmic magnification effect, astronomers have spotted what could be the most distant galaxy ever seen. Light from the young galaxy captured by the orbiting observatories first shone when our 13.7-billion-year-old universe was just 500 million years old.

The far-off galaxy existed within an important era when the universe began to transit from the so-called cosmic dark ages. During this period, the universe went from a dark, starless expanse to a recognizable cosmos full of galaxies. The discovery of the faint, small galaxy opens a window onto the deepest, most remote epochs of cosmic history.

"This galaxy is the most distant object we have ever observed with high confidence," said Wei Zheng, a principal research scientist in the department of physics and astronomy at Johns Hopkins University in Baltimore who is lead author of a new paper appearing in Nature. "Future work involving this galaxy, as well as others like it that we hope to find, will allow us to study the universe's earliest objects and how the dark ages ended."

Light from the primordial galaxy traveled approximately 13.2 billion light-years before reaching NASA's telescopes. In other words, the starlight snagged by Hubble and Spitzer left the galaxy when the universe was just 3.6 percent of its present age. Technically speaking, the galaxy has a redshift, or "z," of 9.6. The term redshift refers to how much an object's light has shifted into longer wavelengths as a result of the expansion of the universe. Astronomers use redshift to describe cosmic distances.

Unlike previous detections of galaxy candidates in this age range, which were only glimpsed in a single color, or waveband, this newfound galaxy has been seen in five different wavebands. As part of the Cluster Lensing And Supernova Survey with Hubble Program, the Hubble Space Telescope registered the newly described, far-flung galaxy in four visible and infrared wavelength bands. Spitzer measured it in a fifth, longer-wavelength infrared band, placing the discovery on firmer ground.

Objects at these extreme distances are mostly beyond the detection sensitivity of today's largest telescopes. To catch sight of these early, distant galaxies, astronomers rely on gravitational lensing. In this phenomenon, predicted by Albert Einstein a century ago, the gravity of foreground objects warps and magnifies the light from background objects. A massive galaxy cluster situated between our galaxy and the newfound galaxy magnified the newfound galaxy's light, brightening the remote object some 15 times and bringing it into view.

Based on the Hubble and Spitzer observations, astronomers think the distant galaxy was less than 200 million years old when it was viewed. It also is small and compact, containing only about 1 percent of the Milky Way's mass. According to leading cosmological theories, the first galaxies indeed should have started out tiny. They then progressively merged, eventually accumulating into the sizable galaxies of the more modern universe.

These first galaxies likely played the dominant role in the epoch of reionization, the event that signaled the demise of the universe's dark ages. This epoch began about 400,000 years after the Big Bang when neutral hydrogen gas formed from cooling particles. The first luminous stars and their host galaxies emerged a few hundred million years later. The energy released by these earliest galaxies is thought to have caused the neutral hydrogen strewn throughout the universe to ionize, or lose an electron, a state that the gas has remained in since that time.

"In essence, during the epoch of reionization, the lights came on in the universe," said paper co-author Leonidas Moustakas, a research scientist at NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, Calif.

Astronomers plan to study the rise of the first stars and galaxies and the epoch of reionization with the successor to both Hubble and Spitzer, NASA's James Webb Telescope, which is scheduled for launch in 2018. The newly described distant galaxy will likely be a prime target.

For more information about Spitzer, visit http://www.nasa.gov/spitzer . For more information about Hubble, visit: http://www.nasa.gov/hubble .


 
 
Whitney Clavin 818-354-4673
Jet Propulsion Laboratory, Pasadena, Calif.
whitney.clavin@jpl.nasa.gov
J.D. Harrington 202-358-5241
Headquarters, Washington
j.d.harrington@nasa.gov
2012-294

本文来源:http://www.nasa.gov/mission_pages/spitzer/news/spitzer20120919.html

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