For the first time, a black hole has been seen being born out of an exploding star just 20 times the mass of our sun -- right in our cosmic neighborhood.
The baby black hole is located in the M-100 galaxy, which is about 50 million light-years from Earth. This makes it far, far closer than the gamma ray blasts seen billions of light-years away at the edge of the visible universe, which are thought to be the newborn wailings of an entirely different sort of black hole -- those with millions of times the mass of our sun which reside at the centers of galaxies.
"What makes this really exciting is that we know the birth date of this black hole," said astrophysicist Kimberly Weaver of NASA's Goddard Space Flight Center. Weaver said today at a NASA press conference about the discovery. "This is a very important result to be able to pinpoint a birth date of a black hole for the first time."
That birth date is in April 1979, when the supernova explosion that signaled the collapse of the star was spotted flaring brightly in the M-100 galaxy by a school teacher using a telescope.
"We know of several dozen stellar black holes in our galaxy but don't know their ages," said Alex Filippenko, an astrophysicist at the University of California at Berkeley.
As a result, it's not been possible before to study an infant black hole anywhere, especially nearby. "In essence, this object occurred almost in our backyard," he added.
There are a number of kinds of stellar explosions that can produce supernovae -- which are short-lived, extra bright stellar events. What makes this one -- dubbed SN 1979C -- special is that it has been observed over the years with a series of orbiting x-ray telescopes, most lately the Chandra X-Ray Observatory. Those observations have revealed that SN 1979C has not dimmed in the 31 years since its birth, as would be expected if this was anything less than a genuine black hole.
This lack of dimming suggests the new black hole is gorging on as much matter as it can handle, said Avi Loeb of the Harvard-Smithsonian Center for Astrophysics. It's the tearing apart of that matter as it falls into the black hole that creates the X-rays.
The discovery is also important because it could help sort out the fates of many other stars, said Filippenko. Theoretically, stars that are greater than about 20 times the mass of our sun are thought to implode and become black holes. Stars a little less than that mass are thought to collapse into what are called neutron stars -- very dense, dead stars, but not quite so exotic and weird as black holes.
"Astronomers don't know the dividing line between black holes and neutron stars," said Filippenko. And the x-ray data from SN 1979c could help to narrow that down. Specifically, they will be looking to verify that the object is, indeed, acting like a steadily feeding baby black hole and not like an angrily spinning newborn neutron star, or pulsar, which can create a wind powerful particles that light up gas and debris in space around it with loads of x-rays.
"What we see in SN 1979C may be a very young version of the Crab Nebula," said Filippenko, referring to the famous and picturesque 950-year-old "pulsar wind nebula" in our own corner of the Milky Way galaxy.
So, although the researchers favor the baby black hole story over the newborn neutron star, only time and more observations will tell.