Dwarf Galaxy, Galaxy Cluster Abell 1795
A bright, long duration flare may be the first recorded event of a black hole
destroying a star in a dwarf galaxy, as reported in our latest press release.
The dwarf galaxy is located in the galaxy cluster Abell 1795, about 800 million
light years from Earth. A composite image of the cluster shows Chandra X-ray
Observatory data in blue and optical data from the Canada-France-Hawaii
Telescope in red, green and blue. An inset centered on the dwarf galaxy shows
Chandra data taken between 1999 and 2005 on the left and Chandra data taken
after 2005 on the right.
The X-ray flare in the inset provides the key evidence for stellar
destruction. A star that wanders too close to a supermassive black hole should
be ripped apart by extreme tidal forces. As the stellar debris falls toward the
black hole, it should produce intense X-rays as it is heated to millions of
degrees. The X-rays should fade as the hot gas spirals inward.
This discovery was part of an ongoing search of Chandra's archival data for
such events. In the past few years, Chandra and other astronomical satellites
have identified several suspected cases of a supermassive black hole ripping
apart a nearby star. This newly discovered episode of cosmic, black-hole-induced
violence is different because it has been associated with a much smaller galaxy
than these other cases.
The black hole in this dwarf galaxy may be only a few hundred thousand times
as massive as the Sun, making it ten times less massive than the Galaxy's
supermassive black hole. This places it in what astronomers call an
“intermediate mass black hole” category.
Astronomers believe that intermediate mass black holes may be the “seeds”
that ultimately formed the supermassive black holes in the centers of galaxies
like the Milky Way. Finding additional nearby examples should teach us about how
these primordial galaxies from the early universe grew and evolved over cosmic
time.
Two independent studies reported observations of this event. The paper led by
Peter Maksym is available online and was published in the November 1st, 2013
issue of the Monthly Notices of the Royal Astronomical Society. A paper led by
Davide Donato and colleagues is available online and has been accepted for
publication in The Astrophysical Journal.
Image credit: X-ray: NASA/CXC/Univ. of Alabama/W.P. Maksym et al &
NASA/CXC/GSFC/UMD/D. Donato, et al; Optical: CFHT
NASA
Guillermo Gonzalo Sánchez Achutegui
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