Eight New Galaxies Around the Milky Way

Astronomers have found in the last two years almost as many galaxies neighboring the Milky Way - the Earth's galaxy - as found in the previous 70 years: namely 8.

This seems to be the tip of the iceberg and dozens more discoveries are expected in the coming years. "Seven of them are new dwarf galaxies [bound to] the Milky Way, ranging in distance from roughly 100,000 to 700,000 light-years from us," said Daniel Zucker, an astronomer at the University of Cambridge in England. "The new dwarfs are extremely faint and diffuse and contain at most a few million stars each," said Zucker.

To draw a comparison, the Milky Way harbors at least 200 billion stars. "Prevailing theories of galaxy formation and the mysterious substance known as dark matter predict that the Milky Way should have a hundred or more surrounding dwarfs, but until the past few years only 12 were known," Zucker said.

The new "hobbit galaxies" were discovered with the Sloan Digital Sky Survey, which makes a high-resolution map of more than a quarter of the sky and is 80 % accomplished. "If you make a very simple assumption that [dwarf galaxies] are distributed uniformly across the sky, then you get dozens of new satellites that should be out there," Zucker said. "The eighth dwarf galaxy-located about 1.4 million light-years away-is even more exciting," Zucker said. "It is far enough from the Milky Way that it has probably not really been affected much by the Milky Way's gravity," he said. "It's actually free floating."

"The other seven dwarfs are essentially crumbs left over from the galactic mergers that made up the Milky Way about a billion years ago," said Zucker.

While the stars of these galaxies are relatively old, the eighth dwarf, named Leo T, has been producing new stars in the past few million years, a very short amount of time in cosmological terms. As this galaxy harbors large pockets of gas, it has the potential to still form stars. "This is basically the smallest, faintest, star-forming galaxy known by orders of magnitude," Zucker said.

More new dwarf galaxies could shed a light on the enigma of dark matter, which does not give off or reflect light, but compasses the most of the universe mass.