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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