Credit: X-ray: NASA/CXC/U.Texas/S.Post et al,
Infrared: 2MASS/UMass/IPAC-Caltech/NASA/NSF
Because the debris fields of exploded stars, known as supernova remnants, are very hot, energetic, and glow brightly in X-ray light,
NASA's Chandra X-ray Observatory has proven to be a valuable tool in
studying them. The supernova remnant called G299.2-2.9 (or G299 for
short) is located within our Milky Way galaxy, but Chandra's new image of it is reminiscent of a beautiful flower here on Earth.
G299 was left over by a particular class of supernovas called Type
Ia. Astronomers think that a Type Ia supernova is a thermonuclear
explosion - involving the fusion of elements and release of vast amounts
of energy - of a white dwarf star
in a tight orbit with a companion star. If the white dwarf's partner is
a typical, Sun-like star, the white dwarf can become unstable and
explode as it draws material from its companion. Alternatively, the
white dwarf is in orbit with another white dwarf, the two may merge and
can trigger an explosion.
Regardless of their triggering mechanism, Type Ia supernovas have
long been known to be uniform in their extreme brightness, usually
outshining the entire galaxy where they are found. This is important
because scientists use these objects as cosmic mileposts, allowing them
to accurately measure the distances of galaxies billions of light years
away, and to determine the rate of expansion of the Universe.
Traditional theoretical models of Type Ia supernovas generally
predict that these explosions would be symmetric, creating a near
perfect sphere as they expand. These models have been supported by
results showing that remnants of Type Ia supernovas are more symmetric than remnants of supernovas involving the collapse of massive stars.
However, astronomers are discovering that some Type Ia supernova
explosions may not be as symmetric as previously thought. G299 could be
an example of such an "unusual" Type Ia supernova. Using a long
observation from Chandra, researchers discovered the shell of debris
from the exploded star is expanding differently in various directions.
In this new Chandra image, red, green, and blue
represent low, medium, and high-energy X-rays, respectively, detected
by the telescope. The medium energy X-rays include emission from iron
and the hard-energy X-rays include emission from silicon and sulfur.
The X-ray data have been combined with infrared data from ground-based
2MASS survey that shows the stars in the field of view.
By performing a detailed analysis of the X-rays, researchers found
several clear examples of asymmetry in G299. For example, the ratio
between the amounts of iron and silicon in the part of the remnant just
above the center is larger than in the part of the remnant just below
the center. This difference can be seen in the greener color of the
upper region compared to the bluer color of the lower region. Also,
there is a strongly elongated portion of the remnant extending to the
right. In this region, the relative amount of iron to silicon is similar
to that found in the southern region of the remnant.
The patterns seen in the Chandra data suggest that a very lopsided
explosion may have produced this Type Ia supernova. It might also be
that the remnant has been expanding into an environment where the medium
it encountered was uneven. Regardless of the ultimate explanation,
observations of G299 and others like it are showing astronomers just how
varied such beautiful cosmic flowers can be.
A paper describing these results was published in the September 1st, 2014 issue of The Astrophysical Journal, and is available online.
The authors are Seth Post and Sangwook Park from the University of
Texas at Arlington in Texas; Carles Badenes from the University of
Pittsburgh, in Pittsburgh, Pennsylvania; David Burrows from Pennsylvania
State University in University Park, Pennsylvania;
John Hughes from Rutgers University in Piscataway, New Jersey; Jae-Joon
Lee from the Korea Astronomy and Space Science Institute; Koji Mori from
the University of Miyazaki in Japan and Patrick Slane from the
Harvard-Smithsonian Center of Astrophysics in Cambridge, Massachusetts.
NASA's Marshall Space Flight Center in Huntsville, Alabama, manages
the Chandra program for NASA's Science Mission Directorate in
Washington. The Smithsonian Astrophysical Observatory in Cambridge,
Massachusetts, controls Chandra's science and flight operations.
Fast Facts for G299.2-2.9:
Scale: Image is 24 arcmin across (about 114 light years)
Category: Supernovas & Supernova Remnants
Coordinates (J2000): RA 12h 15m 33.80s | Dec -65° 26' 33.90"
Constellation: Musca
Observation Date: 10 pointings between April 9, 2005 and Nov 13, 2010
Observation Time: 186 hours 7 min (7 days 18 hours 7 min).
Obs. ID: 5517, 11098-11101, 13157-13160, 13187
Instrument: ACIS
References: Post, S. et al, 2014, ApJ, 792:L20; arXiv:1406.2190
Color Code: X-ray (Red, Green, Blue), Infrared (Red, Green, Blue)
Distance Estimate: About 16,000 light years
