[vsnet-alert 10525] Hubble Finds a Mystery Object
ljk4 at msn.com
Fri Sep 12 13:21:35 JST 2008
Hubble Finds a Mystery Object
Posted by Alan MacRobert, September 11, 2008
Don't get the idea that we've found every kind of astronomical object there
is in the universe. In a paper to appear in the Astrophysical Journal,
astronomers working on the Supernova Cosmology Project report finding a new
kind of something that they cannot make any sense of.
Now you don't see it, now you do. Something in Bootes truly in the middle of
nowhere apparently not even in a galaxy brightened by at least 120 times
during more than three months and then faded away. Its spectrum was like
nothing ever seen, write the discoverers, with "five broad absorption bands
between 4100 and 6500 Angstroms and a mostly featureless continuum longward
of 6500 Angstroms." Even the cause of the spectral features is unknown.
K. Barbary and others
The project used the Hubble Space Telescope to monitor very distant galaxy
clusters for supernovae. On February 21, 2006, in the direction of a
far-away cluster in Bootes named CL 1432.5+3332.8 (redshift 1.112, distance
8.2 billion light-years), Hubble began seeing something brighten. It
continued brightening for about 100 days and peaked at 21st magnitude in two
near-infrared colors. It then faded away over a similar timescale, until
nothing was left in view down to 26th magnitude. The object brightened and
faded by a factor of at least 120, maybe more.
The mystery object did not behave like any known kind of supernova. It is
not even in any detectable galaxy. "The shape of the light curve is
inconsistent with microlensing," say the researchers. They recorded three
spectra of it and its spectrum, they write, "in addition to being
inconsistent with all known supernova types, is not matched to any spectrum
in the Sloan Digital Sky Survey database" of vast numbers of objects. "We
suggest that the transient may be one of a new class."
What's its distance? That would certainly be a first step to figuring it
out, but only the broadest constraints can be put on its distance. Its lack
of parallax motion means that it can't be closer than about 130 light-years,
and a lack of cosmic hydrogen absorption in its spectrum means that it can't
be farther than 11 billion light-years. That leaves a lot of leeway.
Here is the group's paper with all the details. The lead author is Kyle
Barbary (University of California at Berkeley):
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