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When Cosmic Giants Meet Galactic Dwarfs

By David Reneke

What happens when two different-sized galaxies collide?

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When two different-sized galaxies smash together, the larger galaxy stops the smaller one from making new stars, according to a study of more than 20,000 merging galaxies. The research also found that when two galaxies of the same size collide, both galaxies produce stars at a much faster rate.

Dr Luke Davies of The University of Western Australia node of the International Centre for Radio Astronomy Research says our nearest major galactic neighbour, Andromeda, is hurtling on a collision course with the Milky Way at about 400,000 km/h but “the two won’t smash into each other for another four billion years or so”.

Previously, astronomers thought that when two galaxies smash into each other their gas clouds are churned up and seed the birth of new stars much faster than if they remained separate. However, Davies says that whether a galaxy forms stars more rapidly in a collision, or forms any new stars at all, depends on if it is the big guy or the little guy in this galactic car crash: “When two galaxies of similar mass collide, they both increase their stellar birth rate”.

However, when one galaxy significantly outweighs the other the researchers found that star formation rates are affected for both, but in different ways. The more massive galaxy begins rapidly forming new stars, whereas the smaller galaxy suddenly struggles to make any at all. This...

The full text of this article can be purchased from Informit.