An international team of astronomers has detected the dusty remains of some of the earliest stars to shine on the universe. The light from the galaxy, known as A2744_YD4, left its source when the universe was 600 million years old - only four percent its current age.
The detection was initially made using the Atacama Large Millimeter/submillimeter Array (ALMA), with follow up observations being conducted by the European Southern Observatory's (ESO's) Very Large Telescope (VLT).
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Under normal circumstances, the extreme distance of A2744_YD4, which was located more than 3.5 billion light years from Earth at the point during which the light left the galaxy, would prevent ALMA from making the high-quality observations of the star dust.
However, these were not normal circumstances. The team was able to make use of a phenomenon known as gravitational lensing, whereby the influence of a very massive structure between a target galaxy and a telescope can make the astronomical object appear much closer.
For A2744_YD4, the gravitational lens took the form of the colossal galaxy cluster Abell 2744. Nicknamed the Pandora Cluster, Abell 2744 is believed to be the result of a 350 million-year long collision between four smaller galaxy clusters.
The team believe that the gravitational lensing effect from Abell 2744 which is located roughly 3.5 billion light years from our Sun, is responsible for making A2744_YD4 appear 1.8 times larger than it would without the phenomenon.
A Hubble/ALMA view of the Galaxy Cluster Abell 2744, with the distant galaxy A2744_YD4 blown up in the box
Upon analyzing the data, the team discovered that A2744_YD4 played host to vast quantities of interstellar dust, which was created when some of the earliest generations of stars in the history of our universe ended their lives in dramatic supernovae.
The dust clouds are believed to have a mass roughly the equivalent to six million times that of our Sun, and are predominantly comprised of aluminium, carbon and silicon. The team also detected the presence of ionised oxygen, making A2744_YD4 the most distant and ancient galaxy in which the element has been detected to date.
At the point at which it was observed, the team estimate that the youthful galaxy was birthing stars at a rate of 20 solar masses each year, leading the astronomers to estimate that the newly detected dust was created over a period of around 200 million years.
In our neighbourhood of the galaxy, clouds of interstellar dust are relatively common and represent one of the key materials used in the formation of new stars and planets, such as our own Sun and Earth.
However, around 13 billion years ago – the point in time that we observe A2744_YD4 from today – such clouds of dust were rare. These ancient dust clouds are extremely valuable to astronomers, who can use them to indirectly probe the formation and death of the first stellar generation.
The research paper detailing the findings has been published by the ESO, while the video below provides a summary of the finding.