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Astronomers
have spotted one of the rarest and most extreme galaxy clusters in the universe
and, behind it, an object that shouldn’t exist.
Galaxy
clusters are collections of galaxies that orbit one another and are the most
massive objects in the universe. The newly discovered cluster, first detected
by the Hubble space telescope, is over 500 trillion times the mass of the sun.
It is located approximately 10 billion light-years away. Because looking out
into the distant cosmos means also looking back in time, the cluster formed
during an era when the universe was a quarter its present age.
The
cluster, named IDCS J1426.5+3508, is extreme because during this period in
cosmic history, massive collections of galaxies were just beginning to form.
Only one other cluster of comparable size has been seen at this distance and it
is a lightweight compared to IDCS J1426.5+3508.
Adding
to the object’s strangeness, a mysterious arc of blue light was seen just
behind the galaxy cluster. Astronomers think this indicates another massive
star-forming galaxy located even further away at an even earlier epoch.
Light
from this more distant — and yet unnamed – galaxy has been highly distorted by
an effect known as gravitational lensing. The gargantuan mass of the galaxy
cluster bends and twists light coming from the distant galaxy, creating the
strange blue arc
The
farther galaxy is estimated to be 10 to 13 billion light-years away and have a
mass approximately 70 trillion times the sun.
The
astronomers who spotted the blue arc calculated that the odds of finding such a
massive galaxy so distant in the universe are practically nil: “For the observed
magnitudes we expect to find no arcs over the entire sky as bright,” the team
writes in one of three papers outlining their findings, published online in The
Astrophysical Journal June 26.
Understanding
how these objects came to be could help astronomers determine the history of
galactic evolution throughout the history of the universe. The team hopes that
the eROSITA mission – an x-ray telescope scheduled to launch next year and
study galaxy clusters and dark matter – will provide more information on this
bizarre finding.
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