When the universe was about 3 billion years old, just 20% of its current age, it experienced the most prolific period of star birth in its history. But when NASA’s Hubble Space Telescope and the Atacama Large Millimeter/submillimeter Array (ALMA) in northern Chile gazed toward cosmic objects in this period, they found something odd: six early, massive, ‘dead’ galaxies that had run out of the cold hydrogen gas needed to make stars. Without more fuel for star formation, these galaxies were literally running on empty.
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Source: ScienceDaily