Findings suggest the first galaxies in the universe were more massive than previously thought
Astronomers have detected an extended dark matter halo around an ancient dwarf galaxy.
February 22, 2021
The Milky Way is surrounded by dozens of dwarf galaxies thought to be relics of the first galaxies in the universe. Among the most primitive of these galactic fossils is Tucana II an ultrafaint dwarf galaxy that is about 50 kiloparsecs, or 163,000 light years, from Earth.
Now astrophysicists at the Massachusetts Institute of Technology have detected stars at the edge of Tucana II, in a configuration that is surprisingly far from its center but is caught up in the tiny galaxy s gravitational pull. This is the first evidence that Tucana II hosts an extended dark matter halo a region of gravitationally bound matter the researchers calculated to be three to five times more massive than scientists had estimated.
Astronomers Detect Tremendous Amount of Dark Matter in Dwarf Satellite Galaxy
Scientists have discovered that a small galaxy called Tucana II has a much stronger gravitational pull than expected, which means it is likely home to a large amount of dark matter.
Just as the moon orbits the Earth, many satellite galaxies are orbiting our Milky Way. Tucana II is one of them.
These small galaxies, called dwarf galaxies, are thought to be relics of galaxies formed in the beginning of the universe.
Tucana II is an ultrafaint dwarf galaxy about 163,000 light-years from Earth. To astronomers’ surprise, although Tucana II is small, its gravitational pull can be seen very far from its center, indicating that the dwarf galaxy has a tremendous amount of dark matter within.
Our sun is travelling around the center of the Milky Way at 220 kilometers per second, says Gerry Gilmore with the Institute of Astronomy at the the University of Cambridge, referring to the fact that our Milky Way Galaxy lies inside a sphere, or “halo”, of dark matter that extends out far beyond the luminous Galactic disk, surrounded by a spheroidal halo of old stars and globular clusters, of which 90% lie within 100,000 light-years of the Galactic Center. “If there were no dark matter there, adds Gilmore, if there were just stars, we would be travelling at a ‘mere’ 150 km per second,” Gilmore adds.