August 23, 2012
Astronomers Say Milky Way Not As Unique As Once Thought
Lee Rannals for redOrbit.com - Your Universe Online
A new sky survey has revealed that our Milky Way galaxy may not be as special as scientists had previously thought.
The Milky Way is a fairly common type of galaxy, but being paired up with neighbors like the Magellanic Clouds makes it stick out above the rest, so much so that astronomers thought it could be a one of a kind occurrence.
However, astronomer Dr. Aaron Robotham burst everyone's bubble when searching for groups of galaxies similar to ours using the Galaxy and Mass Assembly survey (GAMA).
“We´ve never found another galaxy system like the Milky Way before, which is not surprising considering how hard they are to spot! It´s only recently become possible to do the type of analysis that lets us find similar groups,” Dr Robotham said.
“Everything had to come together at once: we needed telescopes good enough to detect not just galaxies but their faint companions, we needed to look at large sections of the sky, and most of all we needed to make sure no galaxies were missed in the survey”
Simulations of how galaxies form do not produce many examples similar to the Milky Way and its neighbors, making them a rare sight to see.
Astronomers haven't quite known exactly how rare they are until now, with the discovery of not just one but two exact matches among the hundreds of thousands of galaxies that were a part of the survey.
“We found about 3% of galaxies similar to the Milky Way have companion galaxies like the Magellanic Clouds, which is very rare indeed. In total we found 14 galaxy systems that are similar to ours, with two of those being an almost exact match,” Dr Robotham said.
The Milky Way sits next to the Large and Small Magellanic Clouds, which are visible in the southern hemisphere night sky. Many galaxies have smaller galaxies in orbit next to them, but few have two that are as large as the Magellanic Clouds.
The astronomers found that although the Magellanic Clouds are rare, when they are found they are usually near a galaxy like the Milky Way.
“The galaxy we live in is perfectly typical, but the nearby Magellanic Clouds are a rare, and possibly short-lived, occurrence. We should enjoy them whilst we can, they'll only be around for a few billion more years,” Dr Robotham said.
Image 2 (below): This image shows one of the two ℠exact matches´ to the Milky Way system found in the survey. The larger galaxy, denoted GAMA202627, which is similar to the Milky Way clearly has two large companions off to the bottom left of the image. In this image bluer colors indicate hotter, younger, stars like many of those that are found in our galaxy. Credit: Dr Aaron Robotham, ICRAR/St Andrews using GAMA data.