加载中…采用研究树木年轮的方法破解星系成长之谜
(2013-11-12 14:22:17)
标签：
杂谈 |
分类： 科学与技术 |
http://photos.state.gov/libraries/amgov/3234/Week_1/11042013_PIA17554_jpg_600.jpg
从树干致密的核心向外延展到软质的树皮，一圈圈同心的年轮是时光流逝的标志，记载了树木生长的各个阶段。
银河系的寿命超出树木几十亿年，观察星系成长的过程似乎是不可能的事。但是天文学家可以像生物学家那样，通过解读银河系盘面的环轮破解过去的谜团。科学家利用美国国家航空航天局（NASA）的广域红外线巡天探测卫星（Wide-field Infrared Survey Explorer）和星系演化探测器（Galaxy Evolution Explorer，GALEX）提供的数据，已经获取了关于银河系“由内向外”生长的更多证据，说明一些行星在中心地带爆发成形10到20亿年后，外围又随之诞生了另外一些行星。
这一发现可能会揭开古老的银河系的一个谜。作为研究对象的星系呈红色，不再有新行星形成，故被称为“红色和沉寂”的星系。银河系有着自外围区域发出的惊人数量的紫外线光。紫外线光往往产生于高热量的年轻行星，但银河系曾被认为太古老，不可能容纳如此年轻的行星群。
这个谜的谜底可能是高热量的年老行星。弗吉尼亚州布莱克斯堡（Blacksburg, Virginia）弗吉尼亚理工大学（Virginia Tech University）的萨拉•帕蒂（Sara Petty）是2013年10月的《天文期刊》（Astronomical Journal）中一篇论文的主笔。她和她的同事使用一种新的多波长法说明，该原因不明的紫外线光看来是在较老行星的生命后期产生的，当时行星的外层爆裂，温度升高。
图为被称为NGC 3377的星系。广域红外线巡天探测卫星发射的红外光呈红色，星系演化探测器发射的紫外线光呈绿色和蓝色。星系的中心看似白色。所有三种波长的光同时存在，相互叠加。星系外层大多是紫外线光，因此含有更多的蓝光和绿光。图中的点是位于前端的行星。
韩国首尔延世大学（Yonsei University）资助的研究人员和法国国家太空研究中心（Centre National d’Etudes Spatiales）在星系演化探测器项目上进行了合作。
Read more: http://iipdigital.usembassy.gov/st/chinese/inbrief/2013/11/20131106285862.html#ixzz2kPTCXKq2
Galaxy Growth Examined Like Tree’s Rings
http://photos.state.gov/libraries/amgov/3234/Week_1/11042013_PIA17554_jpg_600.jpg
Beginning at a tree trunk’s dense core and moving out to the soft bark, the passage of time is marked by concentric rings, revealing chapters of the tree’s history.
Galaxies outlive trees by billions of years, making their growth impossible to see. But like biologists, astronomers can read the rings in a galaxy’s disk to unravel its past. Using data from NASA’s Wide-field Infrared Survey Explorer (WISE) and Galaxy Evolution Explorer (GALEX), scientists have acquired more evidence for the “inside-out” theory of galaxy growth, showing that bursts of star formation in central regions were followed 1 to 2 billion years later by star birth in the outer fringes.
The discovery may solve a mystery of elderly galaxies. The galaxies in the study, known as “red and dead” for their red color and lack of new star births, have a surprising amount of ultraviolet light emanating from the outer regions. Often, ultraviolet light is generated by hot, young stars, but these galaxies were considered too old to host such a young population.
The solution to the puzzle is likely hot, old stars. Sara Petty of Virginia Tech University in Blacksburg, Virginia, lead author of a paper appearing in the October 2013 issue of Astronomical Journal, and colleagues used a new multi-wavelength approach to show that the unexplained ultraviolet light appears to be coming from a late phase in the lives of older stars, when they blow off their outer layers and heat up.
In the image above of a galaxy called NGC 3377, infrared light from WISE is colored red and ultraviolet light from GALEX is green and blue. The center of the galaxy appears white, where all three wavelengths of light are present and add up. The outside of the galaxy is mostly ultraviolet light, and thus contains more blue and green. The dots in the picture are stars located in the foreground.
Researchers sponsored by Yonsei University in South Korea and the Centre National d’Etudes Spatiales in France collaborated on the GALEX mission.
Read more: http://iipdigital.usembassy.gov/st/english/inbrief/2013/11/20131104285703.html#ixzz2kPTDthP0
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