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Galaxy 'Missing Link' Uncovered

from the BBC News Online

Astronomers have identified a type of galaxy that represents a "missing link" in our understanding of the Universe. Spiral and elliptical galaxies used to be known exclusively as "blue" and "red," respectively. But two studies, published in a Royal Astronomical Society journal, show that one in five galaxies is a red spiral.

It is now thought the red spirals occur when spiral galaxies grow old without any violent collisions, such as with other galaxies. Astronomers have seen that, in dense regions of space where there is a high concentration of galaxies, there are many old, "red and dead" galaxies which are elliptical or spherical in shape.

These galaxies are presumed to have formed rapidly, early in the history of the Universe. The red light we now see from them is that of their twilight years, showing that new star formation has long since stopped. Elsewhere, comparatively young spiral galaxies still promote star formation, whose emitted light tends towards the blue.