Washington, March 4 (ANI): Astronomers have discovered a relic from the early universe - a star that may have been among the second generation of stars to form after the Big Bang.
Located in the dwarf galaxy Sculptor some 290,000 light-years away, the star has a remarkably similar chemical make-up to the Milky Way's oldest stars.
Its presence supports the theory that our galaxy underwent a "cannibal" phase, growing to its current size by swallowing dwarf galaxies and other galactic building blocks.
"This star likely is almost as old as the universe itself," said astronomer Anna Frebel of the Harvard-Smithsonian Center for Astrophysics.
Dwarf galaxies are small galaxies with just a few billion stars, compared to hundreds of billions in the Milky Way.
In the "bottom-up model" of galaxy formation, large galaxies attained their size over billions of years by absorbing their smaller neighbors.
"If you watched a time-lapse movie of our galaxy, you would see a swarm of dwarf galaxies buzzing around it like bees around a beehive," explained Frebel.
"Over time, those galaxies smashed together and mingled their stars to make one large galaxy - the Milky Way," she said.
If dwarf galaxies are indeed the building blocks of larger galaxies, then the same kinds of stars should be found in both kinds of galaxies, especially in the case of old, "metal-poor" stars.
Surveys over the past decade have failed to turn up any such extremely metal-poor stars in dwarf galaxies, however.
Team member Evan Kirby, a Caltech astronomer, developed a method to estimate the metal abundances of large numbers of stars at a time, making it possible to efficiently search for the most metal-poor stars in dwarf galaxies.
Among stars he found in the Sculptor dwarf galaxy was one faint, 18th-magnitude speck designated S1020549.
Spectroscopic measurements of the star's light with Carnegie's Magellan-Clay telescope in Las Campanas, Chile, determined it to have a metal abundance 6,000 times lower than that of the Sun; this is five times lower than any other star found so far in a dwarf galaxy.
The researchers measured S1020549's total metal abundance from elements such as magnesium, calcium, titanium, and iron.
The overall abundance pattern resembles those of old Milky Way stars, lending the first observational support to the idea that these galactic stars originally formed in dwarf galaxies.
The researchers expect that further searches will discover additional metal-poor stars in dwarf galaxies. (ANI)