An X-ray image of the galactic cluster 3C438, with inset showing a powerful radio galaxy.
To the naked eye, galactic cluster 3C438 looks like any other patch of starry sky. But the Chandra space telescope?s X-ray vision paints an extremely different picture?bursting from the cluster?s center is a cloud of energy equivalent to 1 billion exploding Suns, an event that may be universe?s most energetic ever detected.
Astronomers who made the discovery have whittled down the cause of the cosmic energy burst to two suspects. They think either two dense galaxies are colliding at 4 million mph, or a super-massive black hole is swallowing the mass of 100 stars each year.
?In either scenario, this is one of the most extreme events in the local Universe,? the astronomers write an upcoming edition of the Astrophysical Journal. At more than 13 times hotter than the Sun?s core, the energies found in the cluster rival even the enormous energies seen pouring out of the "bullet cluster."
Ralph Kraft, astrophysicist at the Harvard-Smithsonian Center for Astrophysics in Massachusetts and co-author of a study on the finding, said the burst is equivalent to the ?explosion of an entire galaxy worth of stars all at once.?
Although two plausible explanations for the stellar hotspot exist, Kraft doesn?t buy into the idea of an obese black hole causing the cluster?s terrifying energy burst. Even the largest super-massive black holes couldn?t devour stars at the rate needed to produce the energy seen in 3C438. ?Truthfully, (these values) are hard to believe,? Kraft said.
Radio telescope images of the cluster reveal a more complex story: two mushroom-cloud-like jets spouting from either side of a glowing hotspot, representing a radio galaxy. When superimposed on the X-ray image, the structure sits at the center of an intense energy cloud.
But is the radio galaxy the smoking gun for the cluster?s observed heat? Kraft and his colleagues remain unconvinced. It is "too weak? and can?t account for the large spread of intense energy, according to the study.
?We?re witnessing the collision of two very massive clusters into each other,? he told SPACE.com. ?This is the only thing that could release that much energy.?
Staff Writer Jeanna Bryner contributed to this story.
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