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Click on image for larger version |
Comparison of visible hydrogen emission in the NW filament of
SN 1006 in data taken at the CTIO 0.9m telescope (H-alpha,
continuum-subtracted; Winkler, et al.) in 1998 (shown in green),
and the Hubble ACS data (Raymond et. al) in 2006 (shown in
red). The stellar background is from WFPC2 broadband B, V,
and I data from 2008 (Hubble Heritage Team)
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A delicate ribbon of gas floats eerily in our galaxy. A contrail from an
alien spaceship? A jet from a black-hole? Actually this image, taken by
NASA's Hubble Space Telescope, is a very thin section of a supernova
remnant caused by a stellar explosion that occurred more than 1,000 years
ago.
On or around May 1, 1006 A.D., observers from Africa to Europe to the Far
East witnessed and recorded the arrival of light from what is now called
SN 1006, a tremendous supernova explosion caused by the final death throes
of a white dwarf star nearly 7,000 light-years away. The supernova was
probably the brightest star ever seen by humans, and surpassed Venus as
the brightest object in the night time sky, only to be surpassed by the
moon. It was visible even during the day for weeks, and remained visible
to the naked eye for at least two and a half years before fading away.
It wasn't until the mid-1960s that radio astronomers first detected a
nearly circular ring of material at the recorded position of the supernova.
The ring was almost 30 arcminutes across, the same angular diameter as the
full moon. The size of the remnant implied that the blast wave from the
supernova had expanded at nearly 20 million miles per hour over the nearly
1,000 years since the explosion occurred.
In 1976, the first detection of exceedingly faint optical emission of the
supernova remnant was reported, but only for a filament located on the
northwest edge of the radio ring. A tiny portion of this filament is
revealed in detail by the Hubble observation. The twisting ribbon of light
seen by Hubble corresponds to locations where the expanding blast wave
from the supernova is now sweeping into very tenuous surrounding gas.
The hydrogen gas heated by this fast shock wave emits radiation in visible
light. Hence, the optical emission provides astronomers with a detailed
"snapshot" of the actual position and geometry of the shock front at any
given time. Bright edges within the ribbon correspond to places where the
shock wave is seen exactly edge on to our line of sight.
Today we know that SN 1006 has a diameter of nearly 60 light-years, and it
is still expanding at roughly 6 million miles per hour. Even at this
tremendous speed, however, it takes observations typically separated by
years to see significant outward motion of the shock wave against the grid
of background stars. In the Hubble image as displayed, the supernova would
have occurred far off the lower right corner of the image, and the motion
would be toward the upper left.
SN 1006 resides within our Milky Way Galaxy. Located more than 14 degrees
off the plane of the galaxy's disk, there is relatively little confusion
with other foreground and background objects in the field when trying to
study this object. In the Hubble image, many background galaxies (orange
extended objects) far off in the distant universe can be seen dotting the
image. Most of the white dots are foreground or background stars in our
Milky Way galaxy.
This image is a composite of hydrogen-light observations taken with
Hubble's Advanced Camera for Surveys in February 2006 and Wide Field
Planetary Camera 2 observations in blue, yellow-green, and near-infrared
light taken in April 2008. The supernova remnant, visible only in the
hydrogen-light filter was assigned a red hue in the Heritage color image.
For images and more information about SN 1006, visit:
http://hubblesite.org/news/2008/22
http://heritage.stsci.edu/2008/22
For additional information, contact:
Ray Villard
Space Telescope Science Institute, Baltimore, Md.
410-338-4514
villard@stsci.edu
William Blair
Johns Hopkins University, Baltimore, Md.
410-516-8447
wpb@pha.jhu.edu
The Hubble Space Telescope is a project of international cooperation
between NASA and the European Space Agency (ESA) and is managed by NASA's
Goddard Space Flight Center (GSFC) in Greenbelt, Md. The Space Telescope
Science Institute (STScI) conducts Hubble science operations. The
institute is operated for NASA by the Association of Universities for
Research in Astronomy, Inc., Washington, DC.