Astronomers Discover Another Galaxy Lacking Dark Matter

• Astronomers have identified a third galaxy, DF9, which appears to contain no Dark Matter.
• Measurements of DF9's stellar motions indicate a mass of 100 million Suns, entirely accounted for by visible matter.
• This finding challenges the conventional model of galaxy formation, which posits that most galaxies develop within Dark Matter "halos."

Discovery Details

• The study was conducted by a Yale-led team and published in The Astrophysical Journal on June 16th.
• Lead author Michael Keim utilized the Keck Observatory's Cosmic Web Imager (CWI) to measure the mass of DF9 with high precision.
• DF9 was previously mistaken for a black hole before being identified as a faint dwarf galaxy.

Scientific Implications

• DF9 joins DF2 and DF4 as rare examples of galaxies lacking Dark Matter.
• All three galaxies reside in a linear structure of seven galaxies located 45 million light-years away.
• Evidence suggests these galaxies may have formed during a violent, high-speed galactic collision that stripped gas from Dark Matter halos.
• Researchers claim this strengthens the status of Dark Matter as a physical substance, rather than an error in gravitational theory.

Follow-up Research

• The team is currently using various telescopes, including the new Mothra telescope, to search for residual gas from the suspected collision.
• These efforts aim to validate the proposed formation theory and gain further insights into the nature of Dark Matter.