Universe's 'dimmest-known galaxy' found...

Astronomers have identified the "dimmest galaxy" in the universe, which they claim is full of dark matter and an ideal candidate to search for evidence of the mysterious material.

According to them, the galaxy, known as Segue 1, is one of roughly two dozen dwarf galaxies that orbit the Milky Way -- it sits close to the Sagittarius stream which is a river of stellar debris torn from another dwarf galaxy.

"It is the most dark matter-dominated galaxy in the universe," the 'New Scientist' quoted lead astronomer Marla Geha of Yale University as saying.

So far, only 24 stars are confirmed members of Segue 1. Because it is so dim, the astronomers originally thought it was a tight-knit group of stars called a globular cluster. But follow-up observations suggested it's indeed a dwarf galaxy.

The Yale team measured the velocity of its stars and found they were all moving at roughly five km per second, ten times faster than expected if they were gravitationally bound only by each other.

Although the total brightness of the galaxy adds up to less that 350 times the brightness of the Sun, it must weigh at least 450,000 suns -- and possibly 20 times that amount if it is as large as other dwarf galaxies.

There is little gas in the system, suggesting almost all of that mass seems to be made up of dark matter, the mysterious stuff that makes up most of the universe's mass, according to the astronomers.

In fact, the object is one of a larger group of recently discovered galaxies where dark matter seems to outweigh ordinary matter by a factor of 100 or 1000.

"These galaxies are basically invisible. We did not know these kinds of galaxies existed until a couple of years ago," team member Beth Willman said.

Source: The Hindu