February 13, 2013
Astronomers Discover Youngest Black Hole In Milky Way
Lee Rannals for redOrbit.com — Your Universe Online
A rare explosion from a rotating star may have created the most recent black hole formed in the Milky Way galaxy.
Astronomers using NASA's Chandra X-ray Observatory claim that matter was ejected at high speeds along the poles of a rotating star, creating a supernova remnant, W49B, which may contain a young black hole.
"W49B is the first of its kind to be discovered in the galaxy," said Laura Lopez, who led the study at the Massachusetts Institute of Technology (MIT). "It appears its parent star ended its life in a way that most others don't."
Typically, when a massive star runs out of fuel, the central region of the star collapses. This triggers a chain of events that create a supernova explosion, which are generally symmetrical. However, when material near the poles of this rotating star was ejected, jets shooting away from the star's poles mainly shaped the supernova explosion and its aftermath.
Researchers used Chandra data, and compared it to theoretical models of a star, finding iron in just half of the remnant, while the other half contained elements like sulfur and silicon. When added up, this evidence shows an asymmetric explosion took place.
"In addition to its unusual signature of elements, W49B also is much more elongated and elliptical than most other remnants," co-author Enrico Ramirez-Ruiz of the University of California at Santa Cruz (UCSC), said in a statement. "This is seen in X-rays and several other wavelengths and points to an unusual demise for this star."
The astronomers attempted to search for a neutron star while sifting through more evidence, and searched carefully through Chandra data. However, they found no evidence for a neutron star, which is typically left behind after a supernova explosion. The lack of evidence implies that a black hole may have formed instead.
"It's a bit circumstantial, but we have intriguing evidence the W49B supernova also created a black hole," said co-author Daniel Castro, also of MIT. "If that is the case, we have a rare opportunity to study a supernova responsible for creating a young black hole."
Supernova explosions driven by jets have been linked to gamma-ray bursts (GRBs), but there is no evidence that the W49B supernova produced a GRB.
The team wrote in the Astrophysical Journal that this could be the youngest black hole formed in the Milky Way galaxy, with an age of only about a thousand years.
Another study published in the same journal suggests that black holes may be growing at larger rates than what had previously been thought. Astronomers in this study claim that the cap we once thought existed for certain black holes, may not exist, allowing them to grow to much larger sizes than previously believed.