Distant galaxies dazzle in the infrared.They look like the Clark Kents of galaxies, ordinary and not very bright. But viewed in the infrared, they turn into supergalaxies, seething seethe intr.v. seethed, seeth·ing, seethes 1. To churn and foam as if boiling. 2. a. To be in a state of turmoil or ferment: with a hidden fire. New findings from an orbiting infrared telescope suggest that many galaxies were star-making factories in their youth. Scientists estimate that annually each of these galaxies churned out new stars with a total mass 10 to 700 times that of the sun. At that rate-considerably higher than astronomers had calculated from observations in visible light and the near-ultraviolet-early episodes of star birth would have been even stormier and more intense than researchers have thought. If most galaxies produced stars so prodigiously, they could have formed the bulk of their stars in just 1 billion years. "Essentially, a large fraction of the energy in galaxies is being emitted in the infrared and has not been counted in the ultraviolet and optical," says Michael Rowan-Robinson of Imperial College in London. He reported the findings in London last week at a Royal Astronomical Society This article is about the British Society. For the Canadian Society, see Royal Astronomical Society of Canada. The Royal Astronomical Society (RAS) is a learned society that began as the Astronomical Society of London in 1820 to support astronomical meeting on the Hubble Deep Field The Hubble Deep Field (HDF) is an image of a small region in the constellation Ursa Major, based on the results of a series of observations by the Hubble Space Telescope. It covers an area 144 arcseconds across, equivalent in angular size to a tennis ball at a distance of 100 , a patch of sky imaged in unprecedented detail by 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. (SN: 1/20/96, p. 36). Rowan-Robinson and his colleagues base their results on a survey of the deep field conducted by the Infrared Space Observatory Infrared Space Observatory: see infrared astronomy. Infrared Space Observatory (ISO) European Space Agency satellite that from 1995 to 1998 observed astronomical sources of infrared radiation. The satellite, which carried a 60-cm (24-in. (ISO (1) See ISO speed. (2) (International Organization for Standardization, Geneva, Switzerland, www.iso.ch) An organization that sets international standards, founded in 1946. The U.S. member body is ANSI. ). At wavelengths of 7.5 and 15 micrometers, lSO found seven sources of radiation that were two to three times brighter than they appeared in Hubble's visible-light images. Five of the sources lie so far from Earth that the light they emitted took about half the age of the universe to get here and reveals how the galaxies looked when they were about half their current age. Their infrared brilliance has a simple explanation, notes Rowan-Robinson. In the Milky Way and nearby galaxies, interstellar dust grains absorb the visible light emitted by newborn stars and radiate that energy in the infrared. The same process, he says, appears to be taking place in the galaxies detected by ISO. Critics note that the seven galaxies recorded by ISO rank among the nearest and oldest of those in the Hubble survey (SN: 2/24/96, p. 120) and therefore don't represent galaxies in the first throes throe n. 1. A severe pang or spasm of pain, as in childbirth. See Synonyms at pain. 2. throes A condition of agonizing struggle or trouble: a country in the throes of economic collapse. of star birth. However, "the pattern of what we're seeing may apply to the most distant galaxies as well," Rowan-Robinson says. Mark E. 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). in Baltimore notes that, rather than being powered by star birth, the infrared glow of these galaxies may be driven by a black hole or quasar at their heart. More important, he says, if most galaxies are forming stars at the rate inferred from the handful of galaxies detected by ISO, they would have made far more stars than astronomers observe in the universe today. |
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