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Tuesday, 16 May, 2000, 12:25 GMT 13:25 UK
Galactic line up revealed
Hubble
By BBC News Online science editor Dr David Whitehouse

Two galaxies, one on top of the other, can be seen in this Hubble Space Telescope image which has just been released.

However, it is not a titanic galactic collision. Such events are rare and in many cases they do not cause much disruption, as the colliding galaxies are mostly empty space.

This system, called NGC 3314, consists of two large spiral galaxies that line up one behind the other by chance.

This gives astronomers a rare chance to pick out fine details in the nearer galaxy, because objects in that galaxy are seen in silhouette against the more distant one.

Swirling dust

The foreground spiral galaxy is viewed nearly face-on. Its spiral shape is outlined by young bright star clusters.

Dark swirling lanes of interstellar dust can be seen against the glow of the stars from the background galaxy. This silhouetting shows where the dust clouds are located, and how much light they absorb.

The outer spiral arms of the front galaxy appear to change from bright to dark, as they are projected first against deep space, and then against the bright background of the other galaxy.

In many galaxies, interstellar dust lies only in the same regions as recently formed blue stars. However, in the foreground galaxy, NGC 3314a, there are numerous additional dark dust lanes that are not associated with any bright young stars.

A small, red patch near the centre of the image is the bright nucleus of the background galaxy, NGC 3314b. It is reddened because its light is passing through space containing small particles that scatter all but red light.

This is the same reason why the setting Sun appears red as seen from Earth.


In DepthIN DEPTH
hubble pictureEye on space
10 years of the Hubble Space Telescope
See also:

04 May 00 | Science/Nature
04 Feb 00 | Science/Nature
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