Credit X-ray: NASA/CXC/MIT/L.Lopez et al.;
Infrared: Palomar; Radio: NSF/NRAO/VLA
The highly distorted supernova remnant shown in this image may contain the most recent black hole formed in the Milky Way galaxy. The image combines X-rays from NASA's Chandra X-ray Observatory in blue and green, radio data from the NSF's Very Large Array in pink, and infrared data from Caltech's Palomar Observatory in yellow.
The remnant, called W49B, is about a thousand years old, as seen from
Earth, and is at a distance of about 26,000 light years away.
The supernova explosions that destroy massive stars are generally symmetrical,
with the stellar material blasting away more or less evenly in all
directions. However, in the W49B supernova, material near the poles of
the doomed rotating star was ejected at a much higher speed than
material emanating from its equator. Jets shooting away from the star's
poles mainly shaped the supernova explosion and its aftermath.
By tracing the distribution and amounts of different elements
in the stellar debris field, researchers were able to compare the
Chandra data to theoretical models of how a star explodes. For example,
they found iron in only half of the remnant while other elements such as
sulfur and silicon were spread throughout. This matches predictions for an asymmetric explosion.
Also, W49B is much more barrel-shaped than most other remnants in
X-rays and several other wavelengths, pointing to an unusual demise for
this star.
Chandra X-ray Image of W49B showing just the iron (purple) and silicon (blue).
The authors also examined what sort of compact object the supernova
explosion left behind. Most of the time, massive stars that collapse
into supernovas leave a dense spinning core called a neutron star.
Astronomers can often detect these neutron stars through their X-ray
or radio pulses, although sometimes an X-ray source is seen without
pulsations. A careful search of the Chandra data revealed no evidence
for a neutron star, implying an even more exotic object might have
formed in the explosion, that is, a black hole.
This may be the youngest black hole formed in the Milky Way galaxy,
with an age of only about a thousand years, as viewed from Earth (i.e.,
not including the light travel time). A well-known example of a supernova remnant in our Galaxy that likely contains a black hole is SS433. This remnant is thought to have an age between 17,000 and 21,000 years, as seen from Earth, making it much older than W49B.
The new results on W49B, which were based on about two-and-a-half days of Chandra observing time, appear in a paper
in the February 10, 2013 issue of the Astrophysical Journal. The
authors of the paper are Laura Lopez, from the Massachusetts Institute
of Technology (MIT), Enrico Ramirez-Ruiz from the University of
California at Santa Cruz, Daniel Castro, also of MIT, and Sarah Pearson
from the University of Copenhagen in Denmark.
| FAST FACTS FOR W49B: | |
| Scale: | Image is 8.5 arcmin across (60 light years) |
| Category: | Supernovas & Supernova Remnants |
| Coordinates (J2000): | RA 19h 11m 07s | Dec +09° 06' 00" |
| Constellation: | Aquila |
| Observation Date: | August 18-22, 2011 |
| Observation Time: | 61 hours 7 min (2 days 13 hours 7 min) |
| Obs. ID: | 13440-13441 |
| Instrument: | ACIS |
| Also Known As: | G043.3-00.2 |
| References: | Lopez, L et al 2013, ApJ 764, 50; arXiv:1301.0618 |
| Color Code: | X-ray (Green, Blue); Infrared (Yellow); Radio (Magenta) |
