It’s been believed for some time that there are “dark galaxies” in the universe, gas-rich clusters that don’t have any stars. Until now such galaxies have never been seen, but thanks to the use of the ESO’s Very Large Telescope, the first dark galaxies may have been sighted. Since they’re devoid of stars, very little light is emitted from the galaxies, although they’ve been spotted by the illumination of nearby quasars.
This is the first time that the dark galaxies have been directly observed, previously theorized to be be a part of general galaxy formation by feeding gas to those galaxies with stars. Simon Lilly, a researcher at the ETH Zurich University, says, “We searched for the fluorescent glow of the gas in dark galaxies when they are illuminated by the ultraviolet light from a nearby and very bright quasar. The light from the quasar makes the dark galaxies light up in a process similar to how white clothes are illuminated by ultraviolet lamps in a night club.”
Using the sensitivity of the Very Large Telescope, the team that made the discovery took advantage of a series of long exposures to detect the faint glow of the galaxies. Sebastiano Cantalupo, the lead author behind the study from the University of California, says the plan eventually reaped rewards: “After several years of attempts to detect fluorescent emission from dark galaxies, our results demonstrate the potential of our method to discover and study these fascinating and previously invisible objects.”
Other information was also taken away from the study. The mass of the gas in the galaxies is said to be over one billion times of what’s found in the Sun. The star formation efficiency has also been suppressed over 100 times that of typical galaxies.
[via European Southern Observatory]