NASA scientists working with the Hubble Space Telescope have found two tiny galaxies leaving a stellar void to migrate to a region in space full of intergalactic gas.
The dwarf galaxies known as Pisces A and B have left what is known as the Local Void, a region in the universe that spans about 150 million light-years wide and is populated by only a few galaxies.
The two galaxies have spent most of their life in this vast region of empty space, but the environment here has hampered their evolution.
Now, with gravity pulling from dense areas of the universe, the galaxies are leaving the sparsely populated region and entering a dense area of space, much like migrating to a cosmic big city, where astronomers expect them to grow rapidly and produce millions of stars.
An abundance of young blue stars suggests that the duo is birthing new stars at an accelerated rate. Astronomers think this uptick in star formation could be attributed to a denser supply of intergalactic gas. Intergalactic gas in this crowded region is denser, and here, gas raining down on the galaxies may have triggered the formation of stars.
It is also possible that the galaxies encountered a gaseous filament, which compresses gas in the galaxies sets off star birth. This idea is plausible since astronomers found that the galaxies are at the edge of a filament of dense gas.
The dwarf galaxies are faint and small, making them difficult to find, but astronomers were able to spot them using radio telescopes during a survey that measured the hydrogen content in the Milky Way.
Astronomers initially identified 30 to 50 blobs of dense hydrogen gas as possible galaxies. Pisces A and B were eventually selected as the two most likely candidates of nearby galaxies. Pisces A is located about 19 million light-years, while Pisces B lies about 30 million light-years away from Earth. Hubble Space Telescope helped confirm that both of these are dwarf galaxies.
The biggest galaxies in the universe began their lives as dwarf galaxies, but smaller galaxies collide and form larger galaxies in the process.
"These Hubble images may be snapshots of what present-day dwarf galaxies may have been like at earlier epochs," said lead researcher Erik Tollerud, from the Space Telescope Science Institute in Baltimore.
"Studying these and other similar galaxies can provide further clues to dwarf galaxy formation and evolution."
The findings were published in The Astrophysical Journal on Aug. 11.
