Astronomers Find Oldest Stardust In The Universe, Leftover from the First Stars

Astronomers have reported this week that they may have seen some of the earliest stardust ever created in the cosmos. University of College London astrophysicist Nicolas Laporte—and colleagues—say they have detected stardust in a galaxy, as it was when the universe was only 600 million years old.

Published online in the Astrophysical Journal Letters, on March 8th, the study says, “We are probably seeing the first stardust of the universe,” adding that this discovery could, in fact, help astronomers learn more about a particular period in the early universe known as reionization. During this period, ultraviolet radiation stripped electrons from hydrogen atoms.
The dust came from a galaxy called A2744_YD4, which scientists say is hiding behind a galaxy cluster called Abell 2744. This cluster of stars actually works a bit like a gravitational lens, providing magnification and brightening of this very distant (and, apparently, old) galaxy’s light, roughly twofold. As you might expect, the team observed this galaxy using the ALMA telescope (Atacama Large Millimeter Array) in Chile.

And now the team estimates that this galaxy (A2744_YD4) contained an amount of dust that would be roughly equivalent to six million time the mass of our Sun—with the galaxy’s total stellar mass (the total mass of all the galaxy’s stars) was equal to roughly two billion times the mass of our Sun. They have also measured the rate of star formation to be 20 solar masses per year, compared with the Milky Way galaxy’s one solar mass formation rate per year.
Professor Richard Ellis, of ESO and UCL Physics & Astronomy) explains, “This rate is not unusual for such a distant galaxy, but it does shed light on how quickly the dust in A2744_YD4 formed. Remarkably, the required time is only about 200 million years, so we are witnessing this galaxy shortly after its formation.”

Ellis goes on to say, “With ALMA, the prospects for performing deeper and more extensive observations of similar galaxies at these early times are very promising.”

Similarly, Dr. Laporte has concluded: “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.”

In addition, University of Edinburgh astrophysicist Michal Michalowski—who was not involved with the study—comments, “Dust is ubiquitous in nearby and more distant galaxies, but has, until recently, been very difficult to detect in the very early universe. This paper presents the most distant galaxy for which dust has been detected.”

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