The dying pangs of a massive star may have given rise to the galaxy's most recent black hole and produced the first supernova remnant of its kind ever spotted in the Milky Way.
Supernova remnants are the former guts of a star, spilled out across interstellar space by a violent explosion that ended the star's life. Only fairly massive stars, those weighing 10 times more than our sun, produce supernovas. The remnant in the image above is called W49B and was created when a giant star exploded about 26,000 light-years away. As seen from Earth, the object is only about 1,000 years old.
Most supernova remnants are symmetrical, bursting outward in an ever-expanding bubble. W49B looks more like a punctured balloon than a nice sphere, suggesting it has an unusual origin. Astronomers speculate that for some reason the dying star that gave rise to W49B shot off material near its poles at a much higher speed than from elsewhere on its surface. These would have manifested as enormous jets that cleared away material, producing the barrel shape seen now.
Using data from NASA's Chandra X-ray space telescope, researchers found asymmetric levels of different elements within the remnant. For instance, only half of it showed concentrations of iron while sulfur and silicon were spread evenly throughout. This type of explosion, known as a bipolar supernova, has never been seen before in the galaxy.
Chandra also searched inside the remnant to see what sort of object the star left behind in its death. Intermediate-mass stars will give rise to neutron stars -- heavy, compact objects that emit copious amounts of X-rays or radio pulses. Lack of evidence for these signals suggests that the primogenitor star was slightly more massive and created a black hole when it died.
