A galaxy without dark matter
- Author: Joey Payne Mar 30, 2018,
Mar 30, 2018, 4:45
Researchers were scanning the sky using a telescope called Dragonfly, a clever assembly of 48 Canon 400mm wide-angle photographic lenses coupled with long-range astronomical sensors created to detect very weak objects when they made the unusual discovery. NGC1052-DF2 does reside in a region where such things could conceivably occur, lying near a giant elliptical galaxy with a supermassive black hole at its heart. In spite of the fact that we can't straightforwardly watch it, we know dark matter is there in light of the fact that we can perceive how its gravity influences ordinary matter.
We've never seen dark matter directly. But upon further study, an worldwide team of astronomers was surprised to discover that it had no dark matter, something that has been seen as crucial in the formation of galaxies. Now researchers are pondering possible explanations for this missing dark matter in NGC 1052-DF2.
An unusually transparent galaxy about the size of the Milky Way is prompting new questions for astrophysicists.
Yale's Pieter van Dokkum said, 'We thought that every galaxy had dark matter and that dark matter is how a galaxy begins. They found that the clusters were moving at relatively low speeds - less than 23,000 miles (37,000 km) per hour. Dark matter makes up roughly 27 per cent more, and dark energy another 68 per cent.
Many scientists believe that dark matter - matter that scientists can not see directly - is everywhere in the universe, and helps explain how galaxies hold together.
Only discovered in 2015, ultra-diffuse galaxies are thought to be particularly useful cosmic laboratories for understanding dark matter.
We don't really know what dark matter is and why it exists... or why it doesn't. Then, the gravity from those clumps would attract baryonic matter, forming the stars, planets, and other objects we can actually see within a galaxy.
The team's results will appear in the March 29, 2018, issue of the journal Nature. His favourite: That the galaxy formed in the very early universe in a way astronomers have never seen or understood. Weird and invisible, dark matter has not been directly observed-no one is sure what it is, exactly-but it is key to explaining the movement of galaxies in space. It confounds astronomers' theories of the universe, which says galaxies need dark matter to form. The galaxy is a complete mystery, as everything about it is unusual. 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.
None of these ideas is a flawless fit for the evidence, van Dokkum said.
Van Dokkum plans to use Keck to search for more galaxies like NGC 1052-DF2. Imaging them allowed the research team to determine their motions orbiting the galaxy, which could, in turn, provide a measure of the amount of mass that is involved in keeping the objects in place.
Ultra-Diffuse galaxies had been identified previously in other galaxy clusters.
"Paradoxically, the existence of NGC1052-DF2 may falsify alternatives to dark matter", the authors conclude, noting that those alternatives include both variations of MOND and emergent gravity. You can't get one without the other.
Astronomers will be looking to find other galaxies in the universe. Perhaps it formed from the gases swept up by quasar winds. The information on the 10 globular collections the group tracked revealed them relocating far more gradually compared to would certainly be anticipated.
About a year ago, University of Waterloo researchers captured a composite image that strongly supports the existence of dark matter. "It's like you take a galaxy and you only have the stellar halo and globular clusters, and it somehow forgot to make everything else", noted van Dokkum.