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The mystery of the dead galaxies

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Science  21 Nov 2014:
Vol. 346, Issue 6212, pp. 905-907
DOI: 10.1126/science.346.6212.905

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Summary

In our own Milky Way galaxy, clouds of gas are still condensing and igniting to form new stars. But amid the fertile galaxies, astronomers have found others in which the star-making process has come to a halt. For decades, scientists assumed that such "red, dead" galaxies had simply run out of gas—in other words, used up all the raw material needed for stars to form. A few years ago, however, researchers using the Hubble Space Telescope's new Cosmic Origins Spectrograph found several sterile galaxies that were swimming in vast reservoirs of hydrogen and helium gas. Now astrophysicists are tackling a new mystery: Why do dead galaxies stay dead?

  • * Ann Finkbeiner is a science writer in Baltimore, Maryland.