Here is a BBC article from a month ago, which mentions the detection of a
black hole swallowing matter.
What interested me is yet another prerequisite for life on Earth. It seems
that "supermassive black holes, which have masses of up to one billion
suns, are found at the centres of galaxies" but our galaxy no longer has an
active black hole, otherwise life on Earth would probably be unviable:
"Astronomers believe that in the past our own galaxy may have had an
active black hole at its core. Although it is still there, it is not now being
fuelled by a giant accretion disk. Lucky for us. If it was, then the high-
energy radiation from it might make life very difficult indeed."
This yet more evidence for the fine-tuning design argument in respect of life
on Earth and against the SETI assumption that life in the universe is
common.
Steve
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http://news.bbc.co.uk/hi/english/sci/tech/newsid_422000/422837.stm
BBC Sci/Tech
Tuesday, August 17, 1999 Published at 15:45 GMT 16:45 UK
Black hole detected swallowing matter
In space, no-one could see you disappear into a black hole - until now
By BBC News Online Science Editor Dr David Whitehouse
Astronomers may have detected for the first time the final cry from matter
disappearing into a black hole.
It seems to have been spotted in the centre of a galaxy 100 million light years
away.
The ASCA satellite made the vital observations
A black hole is a region of space where super-dense matter creates a gravity
field so strong that not even light can escape its pull. Black holes can come in
many sizes but it is believed that supermassive black holes, which have
masses of up to one billion suns, are found at the centres of galaxies.
Red shift
Dr Paul Nandra, an astrophysicist at Nasa's Goddard Space Flight Center,
observed the galaxy NGC 3516 using the Advanced Satellite for Cosmology
and Astrophysics (ASCA), a Japanese/US X-ray satellite launched in 1993.
NGC 3516 is a so-called Seyfert galaxy. It is named after the astronomer Carl
Seyfert who in 1943 published a catalogue of strange galaxies that had bright
objects at their centres and peculiar spectra. Since then it has become one of
astronomer's favourite galaxies, possibly holding the clue to the mystery of
black holes at galactic cores.
Dr Nandra detected the emission of X-rays from iron atoms in the gas swirling
around a central, dense object in NGC 3516. The gas is heated to
temperatures of millions of degrees under the force of the object's extreme
gravity.
Dr Nandra said this emission is typical of a black hole observation. But buried
in the typical emission spectrum was a "red-shifted" absorption feature, also
from iron atoms. This feature, says Dr Nandra, suggests that the matter is
moving away from us, at six million miles per hour towards the black hole.
Long, hard look
"The evidence is pretty good," adds Dr Nandra, whose data came from an
unprecedented five days of uninterrupted observation. "You often see
evidence of matter flying out of a black hole, but never falling in. For example,
with ultraviolet telescopes, one also detects absorption lines. But this is
always from matter moving toward us and not into a black hole."
The Hubble Space Telescope has snapped NGC 3516
According to Dr Richard Mushotzky, also from the Nasa Goddard Center and
co-author on the paper, this observation is the first clear detection of an
absorption feature with a red-shift for a black hole.
"Nobody has ever seen direct evidence for inflow," Dr Mushotzky said. "We
know from general physical arguments that the active galaxies are powered
by accretion of gas onto the black hole, but no one's ever seen it. There's a
possibility that these data indicate that we are actually starting to see direct
evidence for accretion."
Accretion occurs when matter accumulates around the black hole faster than
it falls in, forming a swirling disk. Friction within this disk causes it to shine
brightly.
Astronomers believe that in the past our own galaxy may have had an active
black hole at its core. Although it is still there, it is not now being fuelled by a
giant accretion disk.
Lucky for us. If it was, then the high-energy radiation from it might make life
very difficult indeed.
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"I have come to the conclusion that Darwinism is not a testable scientific
theory, but a metaphysical research programme-a possible framework for
testable scientific theories." (Popper K.R., "Unended Quest: An Intellectual
Autobiography", [1974], Open Court: La Salle, Ill., Revised Edition, 1982,
p168)
Stephen E. Jones | sejones@iinet.net.au | http://www.iinet.net.au/~sejones
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