Astronomers baffled by distant galaxy that doesn't have any dark matter

Mar 30, 2018, 01:18
Astronomers baffled by distant galaxy that doesn't have any dark matter

That is, except for one.

DF2 is located in a cluster of galaxies that is dominated by a giant elliptical galaxy designated NGC 1052.

Every galaxy that has been spotted contained a dark matter signature. Similarly, MOND theorists expect to find the most significant observable effects of their modified laws in less massive galaxies like NGC 1052-DF2, and lesser effects in more-massive galaxies.

The slower the objects in a system move, the less mass there is in that system.The team's calculations show that all of the mass in the galaxy could be attributed to the mass of the stars, which means there is nearly no dark matter in NGC1052-DF2."If there is any dark matter at all, it's very little". The researchers initially used Dragonfly to study a different galaxy, one appearing to possess an nearly inconceivably gargantuan amount of dark matter, which was a weird result in and of itself.

The galaxy has very few stars, but many of them are grouped together in unusually bright clusters.

Astronomers have discovered something unusual and unique out in the universe - a galaxy with virtually no dark matter - and perhaps even stranger still, this discovery offers up a validation that dark matter actually exists! Yet that is what Yale University astronomer Pieter van Dokkum and his colleagues have just found, they report in a study published Wednesday in Nature. "This thing is astonishing", said team member Pieter van Dokkum, "a huge blob that you can look through". The team are now turning to look at other ultra-diffuse galaxies to see whether any others are similarly deficient in dark matter. "It is literally a see-through galaxy", he added.

Since 1884 astronomers have invoked dark matter to explain why galaxies do not fly apart, given the speed at which they move within galaxies. "After that, everything else happens: Gas falls into the dark matter halos, the gas turns into stars, they slowly build up, then you end up with galaxies like the Milky Way".

In fact, the best fit for the motion of the globular clusters is a galaxy with no dark matter at all, although the uncertainties are high enough that there could be equal amounts of matter and dark matter present. From those measurements, the team calculated the galaxy's mass. "How do you form such a thing?"

If the current theory is wrong, that will also affect the strategies of the experiments trying to catch dark matter particles on Earth, says Bullock. Yet in this unusual galaxy, the projected signatures of these exotic effects are not seen.

The researchers next used NASA's Hubble Space Telescope and the Gemini Observatory in Hawaii to uncover more details about the unique galaxy. Notwithstanding a blend of ordinary matter, like stars and planets and manatees, galaxies are required to contain dark matter, an undetectable substance that makes up a large portion of the mass in the universe.

The galaxy is about 65 million light-years away in the constellation of Cetus and is about the same size as the Milky Way. Dark matter - matter that we know is there from its effects on gravity, but which emits no radiation that we've been able to detect - is so abundant in our universe that it far outweighs normal matter. Another idea is that it formed from matter spewed out by quasars.

As it has greater mass than normal matter, dark matter is believed to hold the necessary gas together while galaxies are forming.

Ultra-Diffuse galaxies had been identified previously in other galaxy clusters. The object which has been scientifically named as NGC1052-DF2 seems to have no dark matter at all in its vicinity.