Distant galaxy yields evidence of the earliest generation of stars

"The detection of so much dust indicates early supernovae must have already polluted this galaxy," explained astronomer Nicolas Laporte.

By Brooks Hays

March 8 (UPI) -- Scientists have been studying interstellar dust in the earliest, most distant galaxy seen by ALMA, gaining new insight into the formation of stars in the early universe.

In images rendered by ALMA, the galaxy A2744_YD4 appears as it existed when the universe was just 600 million years old, when the first stars and galaxies were still forming.


"Not only is A2744_YD4 the most distant galaxy yet observed by ALMA, but the detection of so much dust indicates early supernovae must have already polluted this galaxy," Nicolas Laporte, an astronomer at University College London, said in a news release.

Cosmic dust is composed of tiny grain of silicon, carbon and aluminium, forged in stars and scatter across interstellar space when stars explode in fiery deaths.

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Scientists were able to study the contents of A2744_YD4 because its light is bent and magnified by a massive intermediary galaxy cluster called Abell 2744 -- a phenomenon known as gravitational lensing.

The accumulation of dust by A2744_YD4 allowed the young galaxy to begin producing new stars at an accelerated rate, roughly 20 new stars per year.

"This rate is not unusual for such a distant galaxy, but it does shed light on how quickly the dust in A2744_YD4 formed," said Richard Ellis, an astronomer at the UCL and the European Southern Observatory. "Remarkably, the required time is only about 200 million years -- so we are witnessing this galaxy shortly after its formation."


The findings -- detailed in the Astrophysical Journal Letters -- suggest the earliest star began forming just a few hundred million years after the birth of the universe.

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