From NASANews@luna.osf.hq.nasa.govTue Dec 12 11:05:22 1995
Date: Mon, 4 Dec 1995 15:31:47 -0500
From: NASA HQ Public Affairs Office <NASANews@luna.osf.hq.nasa.gov>
To: press-release-com@mercury.hq.nasa.gov
Subject: Hubble Finds New Black Hole and Unexpected Mysteries

Donald Savage
Headquarters, Washington, DC              December 4, 1995
(Phone:  202/358-1547)

Jim Sahli
Goddard Space Flight Center, Greenbelt, MD
(Phone: 301/286-0697)

Ray Villard
Space Telescope Science Institute, Baltimore, MD
(Phone: 410/338-4514)

RELEASE:  95-216

HUBBLE FINDS NEW BLACK HOLE AND UNEXPECTED MYSTERIES

       Confirming the presence of yet another super-massive 
black hole in the universe, astronomers using NASA's Hubble 
Space Telescope have also found unexpected new mysteries. 

       The black hole and an 800 light-year-wide spiral-
shaped disk of dust fueling it, are slightly offset from the 
center of their host galaxy, NGC 4261, located 100 million 
light-years away in the direction of the constellation Virgo.

       This discovery is giving astronomers a ringside seat 
to bizarre, dynamic processes that may involve a titanic 
collision and a runaway black hole.  This relatively nearby 
galaxy could shed light on how far more distant active 
galaxies and quasars produce their prodigious amounts of energy. 

       The results are being presented today by the team 
consisting of Laura Ferrarese and Holland Ford of the Johns 
Hopkins University, Baltimore, MD, and Walter Jaffe of the 
Leiden University, the Netherlands, at a press conference at 
the European Space Agency (ESA), Paris, in conjunction with 
the "Science With Hubble Space Telescope II" workshop. 

       "I'm delighted by this new finding.  It doesn't fit 
our expectations, and this should lead us to a new 
understanding of black holes," Ford said.  "The new Hubble 
observations have moved us beyond the question of whether 
black holes exist.  Now we can work on the demographics of 
black holes and address a number of other questions: does 
every galaxy have a black hole?  How do they work in detail?" 

       Predicted by Einstein's general theory of relativity, 
a black hole is an extremely compact and massive object that 
has such a powerful gravitational field that nothing, not 
even light, can escape.  This is the second super-massive 
black hole confirmed by Hubble.  By measuring the speed of 
gas swirling around the black hole, Ford and co-
investigators were able to calculate its mass to be 1.2 
billion times the mass of the Sun, yet concentrated into a 
region of space not much larger than the Solar System.

       The strikingly geometric disk -- which  contains 
enough mass to make 100,000 stars like the Sun --  was first 
identified in Hubble observations made in 1992.  These new 
Hubble images reveal for the first time structure in the disk,
which may be produced by waves or instabilities in the disk.

       The disk is mysterious because it is unusual to find 
dust in elliptical galaxies like NGC 4261, which stopped 
making stars long ago due to the absence of the requisite 
raw materials: interstellar gas and dust.  The most 
conventional explanation is that the disk is the remnant of 
a smaller galaxy that fell into the core of NGC 4261.  The 
black hole will swallow the gas from the intruder over the 
next 100 million years, and in the process produce 
spectacular fireworks, researchers predict. 

       Such collisions may have been more common in the 
past, when the expanding universe was smaller.  This would 
help explain the abundance of quasars and active galaxies in 
the distant past.  However, according to theoretical 
simulations, it's difficult, dynamically, to get an intruder 
galaxy to plunge directly into a galaxy's core.  Another 
possibility is that dust ejected from ancient stars in the 
galaxy has fallen into the core and formed a disk.  But this 
does not explain why the disk is off-center, which is 
evidence for a dynamic close encounter.

       Equally as puzzling is the discovery that the black 
hole is offset from the center of the galaxy, and the disk's 
center as well.  Astronomers say that because the black hole 
is the astronomical equivalent of the "800-pound  gorilla," 
what can move it around?  Presumably, the black hole was 
once at the center of the galaxy, but something has pulled 
it 20 light-years from the center, according to the Hubble 
observations.  However, the black hole is so massive, 
scientists are searching for some way to explain how it 
could have been moved.

       One exotic idea is that the black hole is self-
propelled.  The cold, dusty disk serves as a rocket "fuel 
tank" by feeding material onto the black hole where gravity 
compresses and heats it to tens of millions of degrees.  Hot 
gas exhausts out from the black hole's vicinity producing 
the radio jets observed by radio telescopes as twin-lobe 
structures extending far beyond the galaxy.  This exhaust 
may be pushing the black hole across space just like a rocket
engine which propels an object by rapidly ejecting mass.
Radio observations confirm the presence of a jet in NGC4261.

       Hubble is ideally suited for hunting super-massive 
black holes in the universe.  With the astronomical 
equivalent of surgical precision, Hubble's spectrographs can 
measure the rotation of gas near enough to a suspected black 
hole to capture its unmistakable gravitational signature.  
The speed of gas orbiting a black hole will rapidly increase 
toward the center of the disk -- just as the planets closer 
to our Sun orbit faster.

       To date, two other galaxies have confirmed black 
holes.  Hubble detected a 2.4-billion-solar-mass black hole 
identified in the core of elliptical galaxy M87 in 1994, and 
later that year, astronomers using a radio telescope array 
to examine the dynamics of a thin, warped disk of molecules 
deep in the core of spiral galaxy NGC 4258, measured a 40-
million-solar-mass black hole. 

       Ford and his colleagues continue using Hubble to 
survey  both active and quiescent galaxies to determine if 
black holes are commonly found in most galaxies.

       The Space Telescope Science Institute is operated by 
the Association of Universities for Research in Astronomy, 
Inc. for NASA, under contract with the Goddard Space Flight 
Center, Greenbelt, MD.  The Hubble Space Telescope is a 
project of international cooperation between NASA and ESA.

                            - end -

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