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葡京网站:Mystery of the disappearing blue blobs

作者:屈突辂硭    发布时间:2019-02-28 03:17:05    

By Hazel Muir AROUND three billion years ago, the Universe was dominated by blob-like galaxies that were quite unlike anything found in our own neighbourhood of space, according to astronomers in Britain and the US. The researchers used the Hubble Space Telescope to peer into the most distant regions of the Universe and discovered a peculiar new type of galaxy. When astronomers look at the farthest-flung regions of the Universe they are effectively looking back in time, because the light reaching us today has taken billions of years to get here. Astronomers have known since the late 1970s that the youthful Universe contained far more blue galaxies than it does today. Viewed through ground-based telescopes, however, most of these distant galaxies have appeared as indistinct splodges of blue light. “It’s a problem that we’ve been trying to solve since faint blue galaxies were first found in 1978,” says Richard Griffiths of Johns Hopkins University in Baltimore. Griffiths and three colleagues at the University of Cambridge used the Hubble Space Telescope to study 301 galaxies at distances of around three billion light years from the Earth. With the improved resolution possible from above the Earth’s atmosphere, they were able to see the shapes of these galaxies in detail for the first time. They found that around half of them looked similar to the regular spiral and elliptical galaxies which dominate our neighbourhood of space. But the others were a new, very unusual class. “They’re blobby things,” says Griffiths. The galaxies have an irregular or oblong shape and are of even brightness, apart from a few brighter patches. Most are fairly small – roughly a tenth of the size and luminosity of our own Milky Way. Griffiths says that the galaxies’ blue colour and their bright blotches are typical signs of vigorous star formation. About a third of the peculiar galaxies seem to be surrounded by clouds of gas that are gradually falling in towards the galaxy. The researchers do not yet know whether the galaxies all formed in the same way. Another mystery is where they have gone. There are no similar galaxies near to us, so the blobby galaxies that dominated the early Universe must either have somehow disappeared completely or evolved into star systems that look entirely different. Griffiths suggests that they may have merged into other galaxies. Alternatively, they may simply have faded, becoming almost invisible as their stars burnt out. The galaxies may also have become more spherical, due to gravitational interactions among their stars. Astronomers have recently discovered that the sky is full of faint galaxies (New Scientist, Science, 8 April). Some of these, says Griffiths, might be the remnants of the ancient blob-like star systems. Griffiths and his colleagues describe their findings in the current issue of Monthly Notices of the Royal Astronomical Society (vol 273,

 

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