Astronomers have found an ancient galaxy with as much amount of dark matter as present-day galaxies. The finding is counterexample to some earlier studies, which suggest that galaxies don't have much dark matter at the time of their birth and pick up this mysterious matter over time through some unknown process.
Astronomers believe that the visible part of the universe makes up just 5 per cent of it, and the remaining 95 per cent is made up of invisible substances, dubbed dark matter and dark energy. Dark matter does not give off any light, and its existence is inferred only on the basis of its gravitational influence on other observable matter present in the universe.
Astronomers first detected the presence of dark matter in 1970s while investigating spiral galaxies. Since then, observations have suggested that almost all galaxies contain huge quantities of dark matter.
The current research was carried out by Patrick Drew, a graduate student at the University of Texas in Austin, in association with Professor Caitlin Casey and some other astronomers.
Drew was investigating the dusty star-forming galaxies in the universe, when he noticed an ancient galaxy located about 9 billion light-years away from Earth.
The distance of a galaxy from Earth also indicates the time taken by the light to reach Earth from the galaxy.
The team then observed the galaxy using a telescope at a random angle, which enabled them get detailed data about galaxy's rotation curve (the speed of the galaxy's rotation from its centre to its outer boundaries). This specific measurement enables astronomers to determine the amount of dark matter present in a galaxy.
The data revealed that this ancient galaxy, dubbed DSFG850.95, is full of dark matter.
In 2017, a study published in journal Nature had claimed that galaxies in the universe 10 billion years ago were fundamentally different from galaxies in the present-day universe and probably lacked dark matter.
"The galaxy we found is a clear counter-example of that, where it seems to have dark matter behaving in the normal way, as it does in the present-day universe." said Casey.
According to Drew, DSFG850.95 "does what's expected of galaxies like it and it is the first solid confirmation that what happens in these galaxies in the current-day universe is the same as what happened in the early universe."
The findings of the study are published in The Astrophysical Journal.
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