Galactic collision leaves glowing scar

By Richard Stenger
CNN
Friday, October 25, 2002 Posted: 10:05 AM EDT (1405 GMT)
   The blue arc, upper right, is a vestige of a violent merger between a dwarf star group and the larger galaxy Centaurus A, lower image.
The blue arc, upper right, is a vestige of a violent merger between a dwarf star group and the larger galaxy Centaurus A, lower image.
   Story Tools
Save a link to this article and return to it at www.savethis.comSave a link to this article and return to it at www.savethis.com\xA0 Email a link to this articleEmail a link to this article 
Printer-friendly version of this articlePrinter-friendly version of this article  View a list of the most popular articles on our siteView a list of the most popular articles on our site 
   
RELATED
Bigger image of galaxy and arc external link
   
RELATED
Astronomical Journal external link
Johns Hopkins University external link
National Optical Astronomy Observatory external link

(CNN) -- A large galaxy absorbed a smaller companion and left behind a bright blue imprint in the heavens that stretches thousands of light-years across, according to astronomers.

The long blue arc was produced in the wake of a cosmic merger that happened between 200 million and 400 million years ago, scientists said.

When the galaxy Centaurus A tore apart and ate its diminutive neighbor, it sparked the formation of thick bands of young blue stars, which account for the strange cosmic feature.

The Johns Hopkins University researchers had not intended to search for vestiges of dwarf galaxies when they spotted it in high-resolution telescope images.

"One of the joys of science is unexpected discoveries," said Holland Ford, one of the JHU astronomers, in a statement.

"Although our pictures were taken for another project, we decided to search the data for evidence of shredded dwarf galaxies. We were very excited when the blue arc popped out of one of the images."

Ford and colleagues, who announced their find this month, theorize that such cases of galactic gobbling contribute to the formation of halos on the outer boundaries of galaxies.

Such halos are astronomical artifacts, which can help scientists piece together cosmic events that shape galaxies over billions of years.

"Time scales for things to happen in halos are very long, which means they may preserve conditions that reveal how a galaxy formed and evolved," said Eric Peng, lead author of the report to be published in the December issue of the Astronomical Journal.

In the case of Centaurus A, an ellipse or elongated galaxy 10 million light-years away, there are signs that it collided with another large galaxy before consuming its tiny neighbor.

The cosmic feast could herald what happens in our galactic neighborhood several billion years from now.

"When our galaxy merges with the Andromeda Galaxy in the distant future, the Milky Way's satellite galaxies ... will likely be involved in that merger," Peng said.

jos   

Evo malo i nase galaksije

The Milky Way

Our own galaxy is called the Milky Way. It contains about 200 billion stars and can be seen on a very dark night as a bright band stretching across the sky. It is a spiral galaxy, so wide that light would take 100 000 years to travel across it, and so thick that it would take 5000 years for light to pass through it. Our Sun is in one of the spiral arms, called the Orion arm, about two-thirds of the way from the centre. It moves around the centre of the galaxy just like the planets move around the Sun, and each of these orbits takes 200 million years.

The centre of the Milky Way appears to be in the constellation of Sagittarius. Astronomers now think that there is a black hole there.

We cannot see the spiral structure of the Milky Way because we are inside it. Instead we look at other spiral galaxies to try to understand our own.

The pictures below show two spiral galaxies like our own. If they were the Milky Way, the Sun would be about two-thirds of the way to the edge. This has been marked on the pictures to show where the Sun would be in our own galaxy.

jos

jedna od mene

wow slike su za 

dobre su