Galactic growth spurts.Galaxies are like people. They grow when they're young and stop growing when they settle into adulthood. Now, scientists have discovered a galaxy that's been growing in fits and starts. Its name is Leo A. After the galaxy formed, it grew normally. But it soon stopped growing until about halfway through its life, according to new evidence from 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. . Then, surprisingly, Leo A started growing again. [ILLUSTRATION OMITTED] The strange-growing galaxy "has the potential to change the way astronomers build theoretical models for galaxy evolution," says Andrew Cole of the University of Minnesota (body, education) University of Minnesota - The home of Gopher. http://umn.edu/. Address: Minneapolis, Minnesota, USA. in Minneapolis. Leo A is 2.6 million light-years from Earth, which is relatively close as galaxies go. It is so small that scientists refer to it as a dwarf galaxy. Cole and his colleagues observed Leo A using Hubble's sharpest camera, the Advanced Camera for Surveys The Advanced Camera for Surveys (ACS) is a third generation axial instrument aboard the Hubble Space Telescope (HST). The initial design and scientific capabilities of ACS were defined by a team based at Johns Hopkins University. . That camera died in February, but the scientists were able to look at Leo A before the glitch happened. The Hubble data revealed something odd: Only 10 percent of Leo Leo, in astronomy Leo [Lat.,=the lion], northern constellation lying S of Ursa Major and on the ecliptic (apparent path of the sun through the heavens) between Cancer and Virgo; it is one of the constellations of the zodiac. A's stars are ancient. The rest didn't start burning until about 7 billion years ago. It appears, the scientists suggest, that Leo A was lying low from some time 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. 13.7 billion years ago until about 7 billion years ago, when growth resumed. Scientists have never seen another galaxy like it. Leo A is different from previously studied dwarf galaxies in other ways too. For one thing, it has no large galaxies nearby to disturb it. And because it is close to Earth, it's a good place to study when scientists want to test new theories about how galaxies form. "We really don't know Don't know (DK, DKed) "Don't know the trade." A Street expression used whenever one party lacks knowledge of a trade or receives conflicting instructions from the other party. how different Leo A might be from other isolated galaxies; it could be that the delay turns out to be a common feature," Cole says. The scientists are trying to determine why Leo A took such a long break. They've already suggested one possible reason. Stars form in galaxies when the gas inside is cold. Hubble's data, however, show that warm gas spread throughout Leo A. Cole suspects that an ancient string of explosions might have warmed the galaxy and squelched squelch v. squelched, squelch·ing, squelch·es v.tr. 1. To crush by or as if by trampling; squash. 2. star formation for a long time. What brought back its growth spurt 7 billion years ago? That remains a mystery. -- E. Sohn |
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