NASA Space Observatories Glimpse Faint Afterglow
of Nearby Stellar Explosion
Intricate wisps of glowing gas float amid a myriad
of stars in
this image created by combining data from NASA's
Hubble Space
Telescope and Chandra X-ray Observatory. The gas
is a supernova
remnant, cataloged as N132D, ejected from the explosion
of a
massive star that occurred some 3,000 years ago.
This titanic
explosion took place in the Large Magellanic Cloud,
a nearby
neighbor galaxy of our own Milky Way.
The complex structure of N132D is due to the expanding
supersonic
shock wave from the explosion impacting the interstellar
gas of
the LMC. Deep within the remnant, the Hubble visible
light image
reveals a crescent-shaped cloud of pink emission
from hydrogen gas,
and soft purple wisps that correspond to regions
of glowing oxygen
emission. A dense background of colorful stars in
the LMC is also
shown in the Hubble image.
The large horseshoe-shaped gas cloud on the left-hand
side of
the remnant is glowing in X-rays, as imaged by Chandra.
In order
to emit X-rays, the gas must have been heated to
a temperature of
about 18 million degrees Fahrenheit (10 million
degrees Celsius).
A supernova-generated shock wave traveling at a
velocity of more
than four million miles per hour (2,000 kilometers
per second) is
continuing to propagate through the low-density
medium today. The
shock front where the material from the supernova
collides with
ambient interstellar material in the LMC is responsible
for these
high temperatures.
It is estimated that the star that exploded as
a supernova to
produce the N132D remnant was 10 to 15 times more
massive than
our own Sun. As fast-moving ejecta from the explosion
slam into the
cool, dense interstellar clouds in the LMC, complex
shock fronts
are created.
A supernova remnant like N132D provides a rare
opportunity for
direct observation of stellar material, because
it is made of gas
that was recently hidden deep inside a star. Thus
it provides
information on stellar evolution and the creation
of chemical
elements such as oxygen through nuclear reactions
in their cores.
Such observations also help reveal how the interstellar
medium (the
gas that occupies the vast spaces between the stars)
is enriched with
chemical elements because of supernova explosions.
Later on, these
elements are incorporated into new generations of
stars and their
accompanying planets.
Visible only from Earth's southern hemisphere,
the LMC is an irregular
galaxy lying about 160,000 light-years from the
Milky Way. The supernova
remnant appears to be about 3,000 years old, but
since its light took
160,000 years to reach us, the explosion actually
occurred some 163,000
years ago.
This composite image of N132D was created by the
Hubble Heritage
team from visible-light data taken in January 2004
with Hubble's
Advanced Camera for Surveys, and X-ray images obtained
in July 2000
by Chandra's Advanced CCD Imaging Spectrometer.
This marks the first
Hubble Heritage image that combines pictures taken
by two separate
space observatories. The Hubble data include color
filters that sample
starlight in the blue, green, and red portions of
the spectrum, as
well as the pink emission from glowing hydrogen
gas. The Chandra
data are assigned blue in the color composite, in
accordance with the
much higher energy of the X-rays, emitted from extremely
hot gas. This
gas does not emit a significant amount of optical
light, and was
only detected by Chandra.
Image Credit: NASA, ESA, and The Hubble Heritage
Team (STScI/AURA)
Acknowledgment: J.C. Green (Univ. of Colorado) and
the Cosmic Origins
Spectrograph (COS) GTO team; NASA/CXO/SAO |
