Distant galaxy making stars 2000 times faster than Milky Way
Washington: Astronomers using Europe's Herschel Space Observatory have discovered an extremely distant galaxy making stars more than 2000 times faster than our own Milky Way.
Seen at a time when the Universe was less than a billion years old, its mere existence challenges our theories of galaxy evolution.
The galaxy, known as HFLS3, appears as little more than a faint, red smudge in images from the Herschel Multi-tiered Extragalactic Survey (HerMES). Yet appearances can be deceiving: this small smudge is actually a star-building factory, furiously transforming gas and dust into new stars.
Our own Milky Way makes stars at a rate equivalent to one solar mass per year, but HFLS3 is seen to be churning out new stars at more than two thousand times more rapidly. This is one of the highest star formation rates ever seen in any galaxy.
The extreme distance to HFLS3 means that its light has travelled for almost 13 billion years across space before reaching us. So the researchers therefore see it as it existed in the infant Universe, just 880 million years after the Big Bang or at 6.5 percent of the Universe's current age.
Even at that young age, HFLS3 was already close to the mass of the Milky Way, with roughly 140 billion times the mass of the Sun in the form of stars and star-forming material. After another 13 billion years, it should have grown to be as big as the most massive galaxies known in the local Universe.
This makes the object an enigma. According to current theories of galaxy evolution, galaxies as massive as HFLS3 should not be present so soon after the Big Bang.
The first galaxies to form are expected to be relatively small and lightweight, containing only a few billion times the mass of our Sun. They form their first stars at rates of a few times that experienced by the Milky Way today.
The small galaxies then grow by feeding off cold gas from intergalactic space and by merging with other small galaxies. So, finding the age at which the first massive galaxies appeared can constrain galaxy evolution theories. But this is not easy.
"Looking for the first examples of these massive star factories is like searching for a needle in a haystack; the Herschel dataset is extremely rich," said Dominik Riechers of Cornell University, who led the investigation.