Stupefied astronomers on Wednesday unveiled the first and only known galaxy without dark matter, the invisible and poorly-understood substance thought to make up a quarter of the Universe.
According to the latest astronomical models, dark matter appears to be ubiquitous, accounting for 26.8% of the mass of the universe (matter as we know it only accounts for 4.9%, and the rest 68.3% comes from dark energy - but let's not get into that now).
Dokkum's team used the Keck telescopes in Hawaii to track the motion of several star clusters - each with about 100,000 stars - within the galaxy. A Yale-led research team made the discovery while peering at the distant galaxy NGC 1052-DF2. "It's so rare, particularly these days after so many years of Hubble, that you get an image of something and you say, 'I've never seen that before.' This thing is astonishing: a very big blob that you can look through". It's a literally a transparent galaxy.
Scientists can figure out how much mass there is in a galaxy by tracking how fast things inside move, Pieter van Dokkum, one the authors of a new research paper published in Nature, told Newsweek. To arrive at this conclusion, they measured the speeds of 10 twinkly blobs in the galaxy, called globular clusters, that each contain millions of stars. How could this galaxy have formed?
Scientists have discovered a galaxy with nearly no dark matter.
The universe's ordinary matter includes things like gas, stars, black holes and planets, not to mention shoes, umbrellas, platypuses and whatever else you might see on Earth.
Is this the end for dark matter? "Now it seems that at least some galaxies exist with lots of stars and gas and hardly any dark matter". So even among this unusual class of galaxy, NGC 1052-DF2 is an oddball. They no longer rule out that there are probably more ways to create a galaxy than just starting from a dark matter core. More generally, how do you form a galaxy without dark matter? "It challenges the standard ideas of how we think galaxies form".
More news: Nobel Peace Prize victor Malala returns home after over 5 yrsEach of these would certainly have to be analyzed in information to identify if it can develop the distinctive attributes of NGC1052- DF2. By measuring their motions, the astronomers could calculate the mass of material enclosed inside their orbits.
The galaxy, charmingly named NGC1052-DF2, is about 65 million light-years away and is about one two-hundredths the mass of our own Milky Way galaxy. It has much less dark matter than it should have for its size. "So finding the opposite, namely an absence of dark matter, really came out of the blue for us", he said. A galaxy lacking dark matter.
These ideas, however, still do not explain how this galaxy formed.
The researchers suggest that the somewhat-odd appearance of the globular clusters is probably related to the galaxy's unexpected properties, and they announced they're working on a paper that will describe those. But when the team compared them to a better image from the Sloan Digital Sky Survey, they found a surprising mismatch.
"It is conventionally believed to be an integral part of all galaxies, the glue that holds them together and the underlying scaffolding on which they are built", said co-author Allison Merritt from the Max Planck Institute for Astronomy, in Germany.
About a year ago, University of Waterloo researchers captured a composite image that strongly supports the existence of dark matter. NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope.
