Team Finds Ultra-Diffuse Galaxy With 1,000 Times Less Stellar Mass and Almost No Dark Matter
Updated
Updated · Sky at Night Magazine · Jul 15
Team Finds Ultra-Diffuse Galaxy With 1,000 Times Less Stellar Mass and Almost No Dark Matter
1 articles · Updated · Sky at Night Magazine · Jul 15
Summary
Very Large Array observations of gas motion in an ultra-diffuse galaxy showed rotation that can be explained with little—possibly no—dark matter, an unusual result for a small galaxy.
Ultra-diffuse galaxies are giant-sized systems with about 1,000 times less stellar mass than large spirals, yet small galaxies are usually thought to be 80% to 90% dark matter.
Pavel Mancera Piña said one possible explanation is not the total absence of dark matter but an exceptionally low-density distribution unlike standard galaxy-formation models predict.
The finding matters because ordinary matter makes up only about 5% of the universe, so galaxies with minimal dark matter could broaden estimates of how dark matter is distributed—or hint at new physics.
How can finding galaxies with no dark matter actually be the best evidence yet for its existence?
Are these oddball galaxies the first clue that dark matter and dark energy are secretly linked?
Dark Matter-Deficient Galaxies DF2, DF4, and DF9: Evidence, Origins, and Cosmological Impact
Overview
Astronomers have recently discovered 'ghostly galaxies' that are almost entirely devoid of dark matter, offering unique insights into the universe and challenging long-held theories about galaxy formation. These findings provide crucial evidence that dark matter is a distinct physical entity, separate from normal matter. The discovery of galaxies like NGC 1052-DF2 (DF2), which has a very low stellar velocity dispersion and contains little to no dark matter, was a major blow to alternative gravitational theories such as MOND. These breakthroughs are reshaping our understanding of how galaxies form and the true nature of dark matter.