gigantic, dark galaxies probably don't exist after all

After re-analyzing existing Hubble data, astronomers have determined that the extremely faint galaxy Dragonfly 44 has far fewer star clusters in its surrounding substance halo than reported previously

Because the number of globular clusters could be a good indicator for the number of matter, this so-called ultra-diffuse galaxy presumably is a standard dwarf galaxy, with the corresponding amount of matter, instead of a galaxy of Milky Way-like proportions that will consist almost entirely of substance as previously thought.

The research that preceded this adjustment, led by Groningen Ph.D. candidate Teymoor Saifollahi, has been accepted for publication in Monthly Notices of the Royal Astronomical Society.

In 2015, astronomers at Yale led by Dutch astronomer Pieter van Dokkum found several extremely faint galaxies within the Coma Cluster (a group of thousands of galaxies 300 million light-years from Earth within the constellation Haar of Berenice). The strange thing about these galaxies was that they occasionally looked as if it would be more massive than our galaxy while producing 100 to 1000 times less light.

After more accurately measuring the mass of the biggest galaxies, they were found to possess an amount of substance that's considered to be normal in dwarf galaxies. However, the biggest galaxy, Dragonfly 44 (DF44), remained an exception. The research group used different methods to work out the matter in DF44 in 2016 and 2017 and located an amount up to that of the Milky Way. this may mean that DF44 was made of 99.99% matter, while only one-hundredth of a percent of its mass came from visible stars. The team reached this conclusion supported the number of globular clusters around the galaxy, which determines the dimensions of the matter halo.

In a new study, astronomers counted the number of globular clusters around DF44 more accurately and came to a far lower number. The new numbers implied a way lower mass and ten times less matter in DF44, an amount appreciate other dwarf galaxies.

Saifollahi stated that dragonfly44 was an outsider of these years that might not be explained with existing models for star formation. Nor could it's produced in cosmological simulations. Now we all know that the result was wrong which DF44 may be a typical dwarf galaxy. it's likely that each one ultra-diffuse galaxy is like this.