A team of astronomers from the Stony Brook University and the National Astronomical Observatory of Japan recently discovered 854 ‘ultra dark galaxies’ using data from the Subaru Telescope.
Before I dive into the specifics about the Subaru Telescope, let’s look at the team’s discovery.
Astronomers believe galaxy clusters are a key environment for this type of galaxy. The 854 galaxies were discovered within the Coma Cluster.
“Not only these galaxies appear very diffuse,” said Jin Koda, principal investigator of the study, “but they are very likely enveloped by something very massive.”
As Koda said, these ‘ultra dark galaxies’ are very diffuse. But, a lot of them are also large. Many of them rival the size of the Milky Way galaxy. Where they differ is the number of stars. The dark galaxies contain just 1/1,000th of the stars that are in our galaxy.
Usually, galaxies that are this big and this diffuse would have trouble staying together due to strong tidal forces within the cluster. Instead, “something very massive” seems to be holding it together. What is it? Scientists aren’t 100 percent sure, but it’s likely excessive amounts of dark matter.
Why did these galaxies go dark?
At some point in the past, these galaxies lost gas needed to form new stars. Due to the sheer number of dark galaxies discovered, it probably has something to do with the galaxy cluster.
This could have happened in several ways including gravitational interactions with nearby galaxies or multiple, simultaneous supernova explosions.
Future observations will look into the history of star formation within these dark galaxies.
Meet the Subaru Telescope
The Subaru telescope is an optical-infrared telescope and sports a large 8.2-meter diameter primary mirror. The mirror alone weighs 25.1 tons. The entire telescope structure clocks in at a massive 612 tons.
The telescope is named after the star cluster Pleiades. The Japanese name for this cluster is ‘Subaru.’
The telescope calls the summit of Mauna Kea, Big Island, Hawaii home. It joins a dozen other telescopes from 11 countries. Why is Mauna Kea such a popular spot for telescopes? The high-altitude and clear nights. Mauna Kea averages 240 clear nights every year.
Check out some of my favorite images from the Subaru telescope below. You can see more here.
Close-up of Andromeda Galaxy
Top image: Each circled galaxy represents one of the ‘ultra dark galaxies’ discovered. Image credits: NAOJ, Subaru Telescope