GALEX Image
How to Spot a Young Galaxy
These animation stills demonstrate that young galaxies are best viewed in ultraviolet light. They consist of artist conceptions of a typical mature galaxy like our own Milky Way (left) and a typical young galaxy (right). The movie begins by showing the pair in visible light, then transitions into ultraviolet views. While young and old galaxies look equally bright when viewed in visible wavelengths, young galaxies are glaringly bright compared to older galaxies in ultraviolet wavelengths. In the final ultraviolet view, the brightness levels have been dimmed to highlight features of the young galaxy.
Young galaxies light up in ultraviolet because they are filled with hot, newborn stars - objects that pack most of their light into ultraviolet wavelengths. Older galaxies have less star-forming activity and thus give off less ultraviolet light. Both young and old stars radiate visible light, so young and old galaxies look similar when viewed in this wavelength.
NASA's Galaxy Evolution Explorer, with its highly sensitive ultraviolet detectors, spotted what appear to be three-dozen massive young galaxies in our corner of the universe. The findings came as a surprise, because astronomers had thought that the universe's "birth-rate" had declined, and that massive galaxies were no longer forming.
The artist conceptions of the mature galaxy are based on images of the nearby galaxy called Messier 81. The artist conceptions of the young galaxy are based on images of the Bearclaw Galaxy.
Credit: NASA/JPL-Caltech
Release Date
December 21, 2004
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