Hubble offers clues to galaxy evolution.Peering deep into space and far back in time, the Hubble Space Telescope Hubble Space Telescope (HST), the first large optical orbiting observatory. Built from 1978 to 1990 at a cost of $1.5 billion, the HST (named for astronomer E. P. Hubble) was expected to provide the clearest view yet obtained of the universe. has found evidence that fully formed elliptical galaxies already existed during the universe's youth - at one-tenth its current age - but spiral galaxies A spiral galaxy is a type of galaxy characterized by a central bulge of old Population II stars surrounded by a rotating disc of younger Population I stars. Spiral galaxies Designation Picture Classification Constellation Apparent Magnitude were still forming. The observations suggest that elliptical galaxies, which take shape over about 1 billion years, formed soon after the Big Bang big bang Model of the origin of the universe, which holds that it emerged from a state of extremely high temperature and density in an explosive expansion 10 billion–15 billion years ago. . In these studies, Hubble researchers assumed an age of 14 billion years for the cosmos. The findings may pose problems for some cosmologists. Models that give a relatively young age for the universe "leave little time for these [ellipticals] to form and evolve to the maturity we're seeing," says Mark Dickinson of the Space Telescope Science Institute The Space Telescope Science Institute (STScI) is the science operations center for the Hubble Space Telescope (HST; in orbit since 1990) and for the James Webb Space Telescope (JWST; scheduled to be launched in 2013). (STScI) in Baltimore. He and other astronomers presented their findings this week at a NASA NASA: see National Aeronautics and Space Administration. NASA in full National Aeronautics and Space Administration Independent U.S. press briefing in Greenbelt, Md. The observations, which may only apply to galaxies in clusters, rank among the first clues to galaxy evolution provided by Hubble since its repair a year ago. In studying galaxy clusters This page lists some of the more interesting galaxy clusters and groups. Defining the limits of galaxy clusters is imprecise as many clusters are still forming. In particular, clusters close to the Milky Way tend to be classified as galaxy clusters even when they are much smaller that existed when the universe was 5 billion years old, Alan Dressler of the Carnegie Observatories in Pasadena, Calif., found a higher proportion of spiral galaxies, many in fragments. Ellipticals were identical to those in today's cosmos. To find a cluster of more distant galaxies, Dickinson's team looked for objects grouped around the radio galaxy 3C324, observed as it appeared when the cosmos was one-third its current age. Using ground-based telescopes, the team found 20 galaxies in the same patch of sky as 3C324. Two of the galaxies lie near the radio galaxy, and the team inferred that the other 18 might lie at the same distance. Orbiting above Earth's wavering atmosphere, Hubble determined the shapes of these galaxies and found that most of the reddest ones were ellipticals. The red color suggests that the galaxies contain lots of old stars. Ellipticals in the nearby, present-day universe appear old and red, and "these galaxies look just the same," Dickinson says. The irregular bluish blu·ish also blue·ish adj. Somewhat blue. blu  ish·ness n. fragments his team also observed could be the
building blocks of spiral galaxies that hadn't yet formed, he adds.
Using Huble to observe the shapes of galaxies as they appeared even further back in time, F. Duccio Macchetto of the European Space Agency European Space Agency (ESA), multinational agency dedicated to the promotion, for exclusively peaceful purposes, of cooperation among European states in space research and technology. and the STScI and Mauro Giavalisco of the STScI found 16 objects that existed some 12 billion years ago. One of them has a pattern of light emission remarkably similar to today's ellipticals. The object could be a primeval elliptical galaxy; if it already has the reddish hue of a galaxy with elderly stars, it might rewrite theories on cosmology. |
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