Now researchers using NASA's Chandra X-ray Observatory may have finally observed the black hole's fatal limit in action. Dark or Light. Gas swirling into a black hole, left, leaves little trace once past the event horizon.
Gas slamming into a neutron star, right, sends a bright signal.
As the gas flowed between the two objects, it became hot enough to emit x-rays, which Chandra can detect with unprecedented sensitivity. The team found the x-ray signals during this passage were about 100 times weaker than when other gas made a similar trek to a neutron star, the researchers reported here 11 January at a meeting of the American Astronomical Society. The weak signal is consistent with the gas crossing the black hole's event horizon and releasing no more x-rays. Gas being sucked into a neutron star, in contrast, hits the star's surface and releases a burst of energy. The evidence sounds plausible to Roeland van der Marel of the Space Telescope Science Institute in Baltimore, Maryland.