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Quasar Pair Q2345+007A,B:
Twin Quasars Tango And It's No Mirage
The Chandra image of the twin quasars Q2345+007 A, B
shows that they are not identical twins. This means
that it is unlikely that they are an optical illusion,
rather, they were probably created by merging
galaxies.
When galaxies collide, the flow of gas onto the
central supermassive black holes of each of the
galaxies can be enhanced, resulting in two quasars. The
light from the quasar pair started its journey toward
Earth 11 billion years ago. Galaxies were about three
times closer together then than they are now, so
collisions were much more likely.
Quasar pairs that are seen close to one another on the
sky and are at the same distance from Earth often turn
out to be an illusion as part of a gravitationally
lensed system. In these cases, the image of a single
quasar has been split into two or more images as its
light has been bent and focused on its way to Earth by
the gravity of an intervening massive object like a
galaxy, or a cluster of galaxies.
The quasar pair Q2345+007 A, B was thought to be such
an illusion because of the remarkably similar patterns
of the light, or spectra, from the pair at both optical
and ultraviolet wavelengths. However no intervening
galaxy or cluster has been found for this pair, leading
to the speculation that the gravitational light-bending
might be caused by a new type of cluster that contains
hot gas and dark matter, but no stars. Such a
“dark cluster” would be invisible to
optical and ultraviolet telescopes, but would be
detectable in X-rays.
The Chandra X-ray images showed no evidence for a
massive dark cluster. Further, the X-ray spectra of the
two quasars were distinctly different, supporting the
idea that they are distinct objects, rather than a
mirage.
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Fast Facts for Quasar
Pair Q2345+007A,B:
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Credit
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NASA/SAO/CXC/P.Green et al.
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Scale
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Image is 30 arcsec per side.
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Category
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Quasars
& Active Galaxies |
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Coordinates
(J2000)
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RA 23h 48m 19.6s | Dec +00º 57'
21.1" |
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Constellation
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Pisces
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Observation
Date
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May 26, 2000 and June 27, 2000
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Observation
Time
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18 hours total
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Obs.
ID
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861
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Color
Code
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colors indicate X-ray energy bands -
red (low), green (medium), and blue
(high)
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Instrument
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ACIS
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Distance
Estimate
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11 billion light years (redshift
z = 2.15)
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Release Date
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March 13, 2002
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