Astronomers find nearest galaxy to the Milky Way
ROYAL ASTRONOMICAL SOCIETY NEWS RELEASE
Posted: November 4, 2003

An international team of astronomers from France, Italy, the UK and Australia has found a previously unknown galaxy colliding with our own Milky Way. This newly-discovered galaxy takes the record for the nearest galaxy to the centre of the Milky Way.

Called the Canis Major dwarf galaxy after the constellation in which it lies, it is about 25000 light years away from thesolar system and 42000 light years from the centre of the Milky Way. This is closer than the Sagittarius dwarf galaxy, discovered in 1994, which is also colliding with the Milky Way. The discovery shows that the Milky Way is building up its own disk by absorbing small satellite galaxies. The research is to be published in the Monthly Notices of the Royal Astronomical Society within the next few weeks.

The discovery of the Canis Major dwarf was made possible by a recent survey of the sky in infrared light (the Two-Micron All Sky Survey or "2MASS"), which has allowed astronomers to look beyond the clouds of dust in the disk of the Milky Way. Until now, the dwarf galaxy lay undetected behind the dense disk.


The tidal forces of the Milky Way slowly pull apart the Canis Major dwarf galaxy (shown here in red). The stars ripped off in this fashion, surround the galaxy in a vast ring. Credit: RAS
 
"It's like putting on infrared night-vision goggles," says team-member Dr Rodrigo Ibata of Strasbourg Observatory. "We are now able to study a part of the Milky Way that has been previously out of sight".

The new dwarf galaxy was detected by its M-giant stars -- cool, red stars that shine especially brightly in infrared light. "We have used these rare M-giant stars as beacons to trace out the shape and location of the new galaxy because its numerous other stars are too faint for us to see," explains Nicolas Martin, also of Strasbourg Observatory. "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 disk."

In this way, the astronomers found the main dismembered corpse of the dwarf galaxy in Canis Major and long trails of stars leading back to it. It seems that streams of stars pulled out of the cannibalised Canis Major galaxy not only contribute to the outer reaches of the Milky Way's disk, but may also pass close to the Sun.


The Canis Major dwarf galaxy (in red) as seen from Earth. This nearby galaxy is currently below the disk of the Milky Way (seen here in blue) and its stars blend in with stars in the distant disk. In reality, the Galactic disk is thicker than is shown (schematically) here, and also the large amount of dust in this direction hides the small galaxy. Credit: RAS
 
Astronomers currently believe that large galaxies like the Milky Way grew to their present majestic proportions by consuming their smaller galactic neighbours. They have found that cannibalised galaxies add stars to the vast haloes around large galaxies. However, until now, they did not appreciate that even the disks of galaxies can grow in this fashion. Computer simulations show that the Milky Way has been taking stars from the Canis Major dwarf and adding them to its own disk - and will continue to do so.

"On galactic scales, the Canis Major dwarf galaxy is a lightweight of about only one billion Suns," said Dr. Michele Bellazzini of Bologna Observatory. "This small galaxy is unlikely to hold together much longer. It is being pushed and pulled by the colossal gravity of our Milky Way, which has been progressively stealing its stars and pulling it apart."

Some remnants of the Canis Major dwarf form a ring around the disk of the Milky Way.

"The Canis Major dwarf galaxy may have added up to 1% more mass to our Galaxy," said Dr Geraint Lewis of the University of Sydney. "This is also an important discovery because it highlights that the Milky Way is not in its middle age - it is still forming."

"Past interactions of the sort we are seeing here could be responsible for some of the exquisite detail we see today in the structure of the Galaxy," says Dr Michael Irwin of the University of Cambridge.

Apollo 12 tribute DVD set

New! Featuring the jovial crew of Pete Conrad, Dick Gordon and Alan Bean, the Apollo 12 mission was struck by lightning shortly after liftoff but proceeded on the second successful exploration voyage to the lunar surface. This three-disc DVD brings the mission to life with extraordinary detail.
 Choose your store:
U.S. - U.K. - E.U. - Worldwide

Fallen Heroes special patch
This special 12-inch embroidered patch commemorates the U.S. astronauts who made the ultimate sacrifice, honoring the crews of Apollo 1, Challenger and Columbia.
 Choose your store:
U.S. - U.K. - E.U. - Worldwide

Women in Space
Women of Space: Cool Careers on the Final Frontier is for girls, young women, and anyone else interested in learning about exciting careers in space exploration. Includes CD-ROM.
 Choose your store:
U.S. - U.K. - E.U. - Worldwide

Mars rover poster
This new poster features some of the best pictures from NASA's amazing Mars Exploration Rovers Spirit and Opportunity.
 Choose your store:
U.S.

Final Shuttle Mission Patch

Free shipping to U.S. addresses!

The crew emblem for the final space shuttle mission is now available in our store. Get this piece of history!
 U.S. STORE
 WORLDWIDE STORE

STS-134 Patch

Free shipping to U.S. addresses!

The final planned flight of space shuttle Endeavour is symbolized in the official embroidered crew patch for STS-134. Available in our store!
 U.S. STORE
 WORLDWIDE STORE

Ares 1-X Patch
The official embroidered patch for the Ares 1-X rocket test flight, is available for purchase.
 U.S. STORE
 WORLDWIDE STORE

Apollo Collage
This beautiful one piece set features the Apollo program emblem surrounded by the individual mission logos.
 U.S. STORE
 WORLDWIDE STORE

Project Orion
The Orion crew exploration vehicle is NASA's first new human spacecraft developed since the space shuttle a quarter-century earlier. The capsule is one of the key elements of returning astronauts to the Moon.
 U.S. STORE


Fallen Heroes Patch Collection
The official patches from Apollo 1, the shuttle Challenger and Columbia crews are available in the store.
 U.S. STORE
 WORLDWIDE STORE

Columbia Report
The official accident investigation report into the loss of the space shuttle Columbia and its crew of seven. Includes CD-ROM.
 Choose your store:
U.S.

Columbia Report
A reproduction of the official accident investigation report into the loss of the space shuttle Columbia and its crew of seven.
 Choose your store:
U.S. - U.K. - E.U. - Worldwide

Mars Panorama

DISCOUNTED! This 360 degree image was taken by the Mars Pathfinder, which landed on the Red Planet in July 1997. The Sojourner Rover is visible in the image.
 Choose your store:
U.S.

Apollo 11 Mission Report
Apollo 11 - The NASA Mission Reports Vol. 3 is the first comprehensive study of man's first mission to another world is revealed in all of its startling complexity. Includes DVD!
 Choose your store:
U.S. - U.K. - E.U. - Worldwide

Rocket DVD
If you've ever watched a launch from Kennedy Space Center, Cape Canaveral, Vandenberg Air Force Base or even Kodiak Island Alaska, there's no better way to describe what you witnessed than with this DVD.
 Choose your store:
U.S. - U.K. - E.U. - Worldwide

Get e-mail updates
Sign up for our NewsAlert service and have the latest news in astronomy and space e-mailed direct to your desktop (privacy note: your e-mail address will not be used for any other purpose).
Enter your e-mail address:

INDEX | PLUS | NEWS ARCHIVE | LAUNCH SCHEDULE
ASTRONOMY NOW | STORE

ADVERTISE

© 2012 Spaceflight Now Inc.