Canis Major dwarf galaxy found... -- AMIGA Astronomy

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Subject: Canis Major dwarf galaxy found...

Author:
Blobrana

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Date Posted: 12:24:21 11/05/03 Wed

An international team of astronomers has found a previously unknown galaxy colliding with our own Milky Way.
Called the Canis Major dwarf galaxy after the constellation in which it lies, the star grouping is about 25,000 light-years away from our Solar System.

Its distinctive red stars are slowly being pulled into the Milky Way and the dwarf will soon lose all its structure.

The nearby galaxy is even closer than the Sagittarius dwarf galaxy, discovered in 1994, which is also colliding with the Milky Way.

The new discovery was made possible because of a recent survey of the sky in infrared light - the Two-Micron All Sky Survey or 2Mass.

Until that survey, the dwarf galaxy lay undetected behind the Milky Way's dense disc of stars.

It was found by its M-giant stars which are cool, red stars that shine especially brightly in infrared light.

M-giant stars can be used to trace out the shape and location of the new galaxy because its numerous other stars are too faint for us to see.

"They are particularly useful stars as we can measure their distances, and so map out the three-dimensional structure of distant regions of the Milky Way disc."

It seems that streams of stars pulled out of the cannibalised Canis Major dwarf galaxy have merged with the outer reaches of the Milky Way's disc. They may even pass close to the Sun.

In recent years, astronomers have found that large galaxies like the Milky Way grow by consuming smaller galaxies.

Computer simulations show that the Milky Way has been taking stars from the Canis Major dwarf and adding them to its own disc.

The Canis Major dwarf galaxy is a lightweight of about only one billion Suns.

Some remnants of the Canis Major dwarf form a ring around the disc of the Milky Way and add up to 1% more mass to our galaxy.

"This is also an important discovery because it highlights that the Milky Way is not in its middle age - it is still forming."

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