Tormented galaxies show effects of nasty neighbours

Space 28 July 2006

New Scientist Default Image

Many new stars are being born in galaxy NGC 1427A, but it is doomed to be ripped apart by its nasty neighbours

(Image: A Reisenegger et al/H Boffin/VLT/ESO)

New Scientist Default Image

The spiral arm on the left side of galaxy NGC 908 has been bent upwards by a near-collision with a passing galaxy

(Image: H Boffin/VLT/ESO)

Two oddly shaped galaxies show the results of violent interactions with gas clouds and other galaxies in new images from the Very Large Telescope (VLT) array in Paranal, Chile.

The first image shows a small galaxy with an arrowhead shape ploughing into intergalactic gas at high speed. The gas is squeezing the galaxy, called NGC 1427A, as it zips through the cloud at 600 kilometres per second. This squeezing has triggered the birth of many new stars.

NGC 1427A is just one-fifth the length of our own galaxy, the Milky Way, just 20,000 light years across. It lies 60 million light years from Earth in a group of galaxies called the Fornax (Furnace) cluster, and looks similar to the Large Magellanic Cloud in our own galaxy’s neighbourhood. Ultimately, the gravity of other galaxies in the Fornax cluster is expected to rip NGC 1427A apart.


Starburst galaxy

The second image (below, scroll down) shows a galaxy, called NGC 908, suffering from a bent spiral arm. The arm on the left is curved upwards compared with the rest of the galaxy. The blue patches are clusters of massive young stars. NGC 908 is referred to as a starburst galaxy because it is giving birth to new stars at a tremendous rate.

The most massive stars explode as supernova a few million years after they are born. Astronomers have spotted two supernovae in NGC 908 in recent years – one in May 2006 and the other in 1994.

A near collision with another galaxy, which has long since left the scene, probably bent NGC 908’s spiral arm and triggered its intense star-forming phase. NGC 908 is 65 million light years from Earth and is 75,000 light years across.

The images of both galaxies were made using the FORS1 and FORS2 instruments on the European Southern Observatory’s VLT.