Our galaxy is surrounded by dozens of dwarf galaxies that scientists believe are the remnants of the very first galaxies in the universe. One of the oldest of these galaxies is an ultra-faint dwarf galaxy called Tucana II, about 163,000 light years from Earth. Astrophysicists at MIT have now discovered stars on the edge of Tucana II that are in a configuration surprisingly far from the center of the galaxy but captured by the galaxy’s gravitational pull.
Researchers believe this is the first sign that Tucana II has an extended halo of dark matter. The atrium is a region of gravity-bound matter researchers that is three to five times as massive as previously assumed. This discovery implies that the first galaxies in the universe were likely also extended and more massive than previously thought.
Researchers have also found that stars outside Tucana II are more primitive than the stars in the core of the galaxy. They believe that this is the first evidence of this type of star imbalance in an extremely faint dwarf galaxy. The unique configuration suggests that the ancient galaxy may have been the product of one of the first mergers in the universe between two infant galaxies, one of which is slightly less primitive than the other.
Researcher Anna Frebel says that this could be the first sign of “galactic cannibalism”. She believes that one galaxy has eaten a slightly smaller and more primitive neighbor and buried stars on the outskirts of the combined galaxy. Tucana II is one of the most primitive dwarf galaxies there is. This statement is based on the metal content of its stars.
Researchers believe that low-metal stars formed very early, when the universe was not producing heavy elements. In the case of Tucana II, a handful of stars around the galactic core had such low metal content that the galaxy was considered the most chemically primitive of all known ultra-faint dwarf galaxies.
Ref: https://www.slashgear.com
