Nicolas Laporte of University College London and a team of international astronomers, used the Atacama Large Millimeter/submillimeter Array to observe A2744 YD4. It is the youngest and most remote galaxy observed by the telescope. The scientists were surprised to find that there was a lot of interstellar dust – it was formed from the death of stars.
Observations from the ESO’s Very Large Telescope confirmed the galaxy age. It was created about 600 million years after the Big Bang.
“Not only is A2744 YD4 the most distant galaxy yet observed by ALMA,” says Nicolas Laporte, “but the detection of so much dust indicates early supernovae must have already polluted this galaxy.”
The interstellar dust is composed of aluminum, silicon and carbon and its just a nanometer across. Those elements are created from the stars and spread across the galaxy when the most enormous of them turn into supernova.
In our time, this dust is abudant, but in the very beginning of the Universe it was very scarce.
Observations of the galaxy A2744 YD4 were possible because it lied right behind a massive galaxy cluster named Abell 2744. Using the gravitational lensing, the astronomers magnified the galaxy by 1.8 times, allowing them to see the early Universe.
These observations also detected oxygen emissions in the young galaxy. This is the earliest detection of oxygen in the Universe.
The detection of the interstellar dust gave us information about the supernovas that occurred and when the Universe basked into the light of the first stars. One of the holy grails of astronomy is determining this cosmic dawn, and the dust may help us probe it indirectly.
The researchers estimated that A2744 YD4’s dust has the mass of 6 million suns, while the galaxy’s total mass is about 2 billion solar masses. The formation of stars there is about 20 star masses per year – over twenty times faster than our Milky Way galaxy.
“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, co-author of the study. “Remarkably, the required time is only about 200 million years — so we are witnessing this galaxy shortly after its formation.”
This suggests that the formation of stars there started 200 million years before the time at which we observe the galaxy. This can give us a incredible opportunity to observe the very first galaxies . Our solar system is the product of the first generation stars, and by observing them, we are exploring our origins.
“With ALMA, the prospects for performing deeper and more extensive observations of similar galaxies at these early times are very promising,” says Ellis.
And the lead author 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.”