Telescope Captures Grouping of Oddball Galaxy and Supernova

The Very Large Telescope has taken one of the best ever images of two galaxies locked in a slow motion, disruptive collision, scientists say.

The image has also given astronomers a peak at an unusual exploding star in the same area of the sky.

The colliding galaxies are known collectively as Arp 261, from Halton Arp?s catalogue of Peculiar Galaxies. With the the FORS2 instrument on the ESO?s Very Large Telescope in Chile, astronomers were able to photograph the oddball in greater detail than ever before.

Arp 261 lies about 70 million light-years away in the constellation of Libra, the Scales. Its chaotic and very unusual structure is the result of the galactic close encounter.

Although individual stars are very unlikely to collide in such an event, the huge clouds of gas and dust in the galaxies crash into each other at high speed, leading to the formation of bright new clusters of very hot stars, which are clearly seen in the picture.

The paths of the existing stars in the galaxies can be dramatically disrupted, creating the faint swirls extending to the upper left and lower right of the image.

Both interacting galaxies were probably dwarfs not unlike the Magellanic Clouds orbiting our own galaxy.

The images used to create this picture were not actually taken to study the interacting galaxies at all, but to investigate the properties of the inconspicuous object just to the right of the brightest part of Arp 261 and close to the centre of the image. This object is an unusual exploding star, called SN 1995N, that is thought to be the result of the final collapse of a massive star at the end of its life, a so-called core collapse supernova.

SN 1995N is unusual because it has faded very slowly ? the glow still shows clearly on this image more than seven years after the explosion took place.

It is also one of the few supernovae to have been observed to emit X-rays. It is thought that these unusual characteristics are a result of the exploding star being in a dense region of space so that the material blasted out from the supernova ploughs into it and creates X-rays.

The image also captured two small asteroids from our Solar System that lie between the orbits of Mars and Jupiter and happened to cross the images as they were being taken. They show up as the red-green-blue trails at the left and top of the picture. The asteroid at the top is number 14670 and the one to the left number 9735. They are probably less than 3 miles (5 kilometers) across.

There is also a star captured at the bottom of the image. Though it appears bright, it is still about one hundred times too faint to be seen with the unaided eye. It is most likely a star like the Sun and about 500 light-years from us.

Arp 261 itself, and the supernova, are about 140,000 times further away again than this star. Much more distant still, perhaps some fifty to one hundred times further away than Arp 261, lies a cluster of galaxies visible on the right of the picture.

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