A cluster of galaxies 7 billion light-years away is forcing astronomers to question much about what they thought they knew about how stars and other celestial bodies are formed. (Photo: NASA)

A cluster of galaxies 7 billion light-years away is forcing astronomers to question much about what they thought they knew about how stars and other celestial bodies are formed. Researchers said the galaxy, which should be dormant, is one of the most active they have ever seen.

"Central galaxies have typically been referred to as 'red and dead' - just a bunch of old stars orbiting a massive black hole, and there's nothing new happening," Michael McDonald, lead author the study, published in the journal Nature, and a researcher at the Massachusetts Institute of Technology, told the Register. "But the central galaxy in this cluster has somehow come to life, and is giving birth to prodigious numbers of new stars."

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The cluster is also brightest when viewed through X-rays, is one of the most massive clusters in the known universe, and has the largest rate of hot gas cooling as well. However, it's also doing something much more interesting, which made scientists refer to it as an undead galaxy.

The cluster, known as the Phoenix Cluster, is creating the equivalent of more than 740 suns every year -- hundreds of times more than our Milky Way galaxy produces.

"If you look at normal galaxy clusters, the central, most massive galaxy is typically forming stars at a rate of one new star every few years," McDonald told NBC News. "It's a huge difference."

Researchers said a black hole in the center of the galaxy should be cooling it off and preventing it from creating stars at such a fast rate. However, that black hole appears to be asleep. Once it wakes, however, the galaxy should fall in line with other galaxies.

"The supermassive black hole lurking in the galaxy's nucleus seems to be asleep at the switch," Brian McNamara, professor of astrophysics at the University of Waterloo, told the Register. "But once the black hole gets going and begins to push the hot atmosphere aside, perhaps in another 100 million years or so, it should shut down cooling and reduce the star formation rate in a feedback process that is active in most galaxy clusters."

While the galaxy appears to break all the rules, researchers said the rules cannot be rewritten based on this one finding alone.

"If we could find more systems like this one, it would imply that this is a normal phase of galaxy cluster evolution," McDonald told NBC News. "To do this, we need deeper surveys that cover larger areas of the sky. We have the technology in place for this - we just need time and continued financial support."