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When researchers from Yale University presented the results of their observations of galaxy NGC1052-DF2 in March 2018, their work was greeted with a mix of praise and criticism.
Their research suggested that the unusual galaxy contained little or no dark matter – the idea contradicted the existing theory of dark matter, which partly explains why it has attracted so much attention.
However, a team led by Pieter van Dokkum, a professor of astronomy from the Sol Goldman family at Yale University, discovered another galaxy that contains no dark matter – a finding that corroborates their initial observations that dark matter is really separable from galaxies.
These discoveries may force us to completely rethink the hypotheses previously adopted on the formation of galaxies.
Although we can not see dark matter, we think it is a big part of the mass of our universe. Our galaxies are composed of dark matter as well as "normal" matter like stars and planets, for example.
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The discovery by scientists of galaxies containing little or no dark matter is unprecedented and seemed somewhat surprising to them.
"Seeing something completely new is really fascinating," said Shany Danieli at the Keck Observatory, which spotted the galaxies for the first time two years ago. "Nobody knew that such galaxies existed, and the best thing in the world for an astronomy student is to discover an object, that it's a planet, a star, or from a galaxy, which no one knew or thought of. "
In order to take a closer look at the galaxies discovered, the research team followed the movements of ten star clusters, allowing them to determine the amount of mass in each galaxy.
Unusually, they discovered that the galaxies contained only a mass equivalent to that of the stars, which means that, most probably, there was probably only normal matter in the galaxy.
The second galaxy found to be devoid of dark matter has been dubbed NGC 1052-DF4 – a discovery as exciting for researchers as the original discovery of DF2.
"This means that the chances of finding more of these galaxies are now higher than expected.Since we have no good idea of how these galaxies were formed, I hope these discoveries will encourage more of these galaxies. scientists to work on this puzzle, "Dokkum told the president. Keck Observatory.
Until recently, it was thought that galaxies could not form without dark matter – but Rita Wechsler of Stanford University told National Geographic: "We need to rethink what is a galaxy."
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Both DF2 and DF4 belong to a relatively new class of galaxies called ultra-diffuse galaxies. According to the Keck Observatory, they are about the same size as the Milky Way but have a lot less stars, which makes them "mellow" and "translucent", which makes them harder to watch. .
Despite the lack of dark matter in these galaxies, their existence further reinforces the theory of dark matter: it reinforces the idea that dark matter is a substance that is not coupled to "normal" matter and shows that they can be found independently of each other. .
The researchers emphasized their hope of continuing to explore new galaxies by stating, "Our hope is that it will allow us to go even further in understanding one of the greatest mysteries of our universe – the nature of dark matter. "
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