Dewayne Washington
Goddard Space Flight Center, Greenbelt, Md. Jan. 9, 2006
(301) 286-0040

Release 06-03

SCIENTISTS FIND BLACK HOLE’S ‘POINT OF NO RETURN’

Scientists using NASA's Rossi X-ray Timing Explorer have compared suspected neutron stars and black holes and found that the black holes behaved as if each one has an event horizon, the theoretical border from beyond which nothing, not even light, can escape.

The team found that X-ray light emitted from these two types of regions behaved differently. As expected, the neutron stars appeared to have a hard surface, which erupts in an X-ray explosion every several hours. The black holes appeared to have no surface. Matter falling toward the black hole seems to disappear into the void.

Dr. Ron Remillard of the MIT Kavli Institute in Cambridge, Mass., led the analysis and discusses his team's result today at a press conference at the 207th meeting of the American Astronomical Society in Washington. His colleagues are Dacheng Lin of MIT and Randall Cooper and Prof. Ramesh Narayan of the Harvard-Smithsonian Center for Astrophysics in Cambridge.

"Event horizons are invisible by definition, so it seems impossible to prove their existence," said Remillard. "Yet by looking at dense objects that pull in gas, we can infer whether that gas crashes and accumulates onto a hard surface or just quietly vanishes. For the group of suspected black holes we studied, there is a complete absence of surface explosions called X-ray bursts. The gas that would fuel such bursts appears to vanish."

The rest of the story is here:

http://www.nasa.gov/centers/goddard/news/topstory/2006/blackhole_noreturn.html

Donna Weaver
Space Telescope Science Institute, Baltimore
(Phone: 410-338-4493)

Rogier Windhorst
Arizona State University, Tempe, Ariz.
(Phone: 480/965-7143)

RELEASE NO.: STScI-PR06-04

GALACTIC MERGERS HELP MONSTER BLACK HOLES GROW

An analysis of the Hubble Space Telescope's deepest view of the universe
offers compelling evidence that monster black holes in the centers of
galaxies were not born big but grew over time through repeated galactic
mergers. The Hubble Ultra Deep Field (HUDF) studies also confirm recent
computer simulations that predict that that newly merging galaxies are
enshrouded in so much dust that astronomers cannot see black holes
feasting on stars and gas from the mergers. The computer simulations,
as supported by Hubble, suggest that it takes hundreds of millions to a
billion years before enough dust clears so that astronomers can see the
black holes feasting on stars and gas from the merger.

For images and additional information about this research on the Web, visit:

http://hubblesite.org/news/2006/04.