Astronomers have spotted the oldest cosmic dust ever discovered, from just 200 million years after the birth of first star-dust that could help us learn more about the origins of our universe.
Cosmic dust is mainly composed of silicon, carbon and Aluminium, in grains as small as a millionth of a centimeter across. The chemical element in these grains are forged inside stars and are scattered across the cosmos when the stars die, most spectacularly in supernova explosion the final fate of short-lived, massive stars. Today this dust is plentiful and is a key building block in the formation of stars, planets and complex molecules; but in early universe, before the first generations of stars died out, it was scarce.
Researchers from university college London in UK says that the find give us new insight into the birth and explosive deaths of the very first stars in the universe.
The observed galaxy is called A2744_YD4, discovered with the Atacama Large Millimeter Array (ALMA) observatory and the very large telescope in Chile.
The observation of the dusty galaxy A2744_YD4 were made possible because this galaxy lies behind a massive galaxy cluster called Abell 2744. A phenomenon called gravitational lensing causes the cluster to act like a giant cosmic ‘Telescope’ magnifying the more distant A2744_YD4 by about 1.8 times, allowing the team to peer far back into the early universe.
“The Hubble and Spitzer space telescope provided us with important information about distance of A2744_YD4, but it’s only thanks to powerful instruments like X-shooter and ALMA that we can confirm the nature of this distant dusty galaxy,” said Guido Roberts-Borsani (UCL physics & astronomy ), PhD student and a co-author of the study.
The detection of cosmic dust in the early universe provides new information on when the first supernovae exploded and hence the time when the first hot stars bathed the universe in light.
The team estimates that A2744_YD4 contained an amount of dust equivalent to 6 million times the mass of our sun, while the galaxy’s total stellar mass (the mass of all its stars) was two billion times the mass of our sun. The team also found that stars are forming in A2744_YD4 at the rate of 20 solar masses per year.
Further measurements of this kind offer the exciting prospect of tracing early star formation and the creation of the heavier chemical elements even further back into the early universe”, concluded Dr. Laporte.