Surprising Discovery Of Unusual Galaxies With No Dark Matter

Eddie Gonzales Jr. – MessageToEagle.com –  Dark matter is a mysterious substance that manifests itself through its gravitational pull. Astronomers have previously thought that this invisible substance typically dominates the makeup of galaxies, but it’s time to re-consider other options.

The discovery of unusual galaxies that contain little to no dark matter offers evidence dark matter is in fact separable from galaxies.

NGC 1052-DF2 – the very first known galaxy to contain little to no dark matter. Credit: Yale University.

Using W. M. Keck Observatory’s Keck Cosmic Web Imager (KCWI), astronomers gathered more precise measurements and found that the globular clusters inside the galaxy are indeed moving at a speed consistent with the mass of the galaxy’s normal matter. If there were dark matter in NGC 1052-DF2, the clusters would be moving much faster.

“No one knew that such galaxies existed, and the best thing in the world for an astronomy student is to discover an object, whether it’s a planet, a star, or a galaxy, that no one knew about or even thought about,” said Shany Danieli, a graduate student at Yale University who first spotted the galaxy about two years ago.

KCWI is an excellent instrument for the study of dark matter because it’s the world’s only telescope that allows to observe the whole galaxy at once. Its high spectral resolution also enables us to measure the mass accurately.

In a press statement, astronomers announce they have now discovered another galaxy devoid of dark matter, named NGC 1052-DF4, or DF4 for short.

“Discovering a second galaxy with very little to no dark matter is just as exciting as the initial discovery of DF2,” said Pieter van Dokkum, Sol Goldman Family Professor of Astronomy at Yale University, who is the lead author on the DF4 paper. “This means the chances of finding more of these galaxies are now higher than we previously thought. Since we have no good ideas for how these galaxies were formed, I hope these discoveries will encourage more scientists to work on this puzzle.”

See also:

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Like DF2, DF4 belongs to a relatively new class of galaxies called ultra-diffuse galaxies (UDGs). They are as large as the Milky Way but have between 100 to 1000 times fewer stars, making them appear fluffy and translucent, therefore difficult to observe.

Ironically, the lack of dark matter in these UDGs strengthens the dark matter theory. It proves that dark matter is a substance that is not coupled to ‘normal’ matter, as both can be found separately. The discovery of these galaxies is difficult to explain in theories that change the laws of gravity on large scales as an alternative to the dark matter hypothesis.

Astronomers next goal is to find out how common these galaxies are and whether they exist in other areas of the universe. Hopefully, this will take us one step further in understanding one of the biggest mysteries in our universe – the nature of dark matter.

Written by Eddie Gonzales Jr. – MessageToEagle.com Staff Writer