I have some astronomy questions

hello

I've been watching "The Universe" on the History Channel and I find that
show to be fascinating. I've learned so much from it but it also generates
questions. If anyone here can help me get clear on a few things I'd really
appreciate it. here are a couple things I've been wondering about.

1) I'm particularly interested in the black hole at the center of our
galaxy... If there is a black hole at the center of our galaxy, is it
sucking in all the stars that are near the center? One of the episodes
stated that when a black hole "eats" a star it creates one of the biggest
events in the universe. So I'm looking at the center of our galaxy and I
see the closer you get the more stars there are, and if there's black hole
in the center, I'm thinking it must be gobbling up stars constantly. Is
that happening?

2) I'm also wondering, if there is a black hole in the center of the galaxy,
are we too far away to receive any of the gravitational pull? When I look
at the galaxy, it reminds me of a bathtub drain. It looks like everything
is swirling and being drawn inwards. Does everything in a galaxy eventually
get sucked into the black hole? Or are we too far away to ever be affected
by the gravity of the black hole at the center?

3) Then I have a question about the big bang. Is it true that everything in
the universe was compacted into something the size of one atom? Did I
really hear that right? If so, does it not follow that every atom and
molecule in my body, and your body, and was there at the big bang? I mean,
I can look at the fingernail on my little pinky toe and consider that it was
there at the big bang... and so was Abraham Lincoln's hat... now that is
cosmic!

Any help on these issues is much appreciated!

Gary in Vermont

"solar bus driver" wrote in message

hello

I've been watching "The Universe" on the History Channel and I find
that show to be fascinating. I've learned so much from it but it
also generates questions. If anyone here can help me get clear on a
few things I'd really appreciate it. here are a couple things I've
been wondering about.

1) I'm particularly interested in the black hole at the center of our
galaxy... If there is a black hole at the center of our galaxy, is it
sucking in all the stars that are near the center? One of the
episodes stated that when a black hole "eats" a star it creates one
of the biggest events in the universe. So I'm looking at the center
of our galaxy and I see the closer you get the more stars there are,
and if there's black hole in the center, I'm thinking it must be
gobbling up stars constantly. Is that happening?

The black hole attracts mass just like any other mass
does, it doesn't reach out and suck things in. Most
material (stars included) will be in an orbit of one
shape or another. Perturbations amongst the bodies
can send some onto paths that cause them to approach
the black hole close enough to tear them apart and
join the accretion disk, eventually spiraling in to
be "consumed".


2) I'm also wondering, if there is a black hole in the center of the
galaxy, are we too far away to receive any of the gravitational pull?
When I look at the galaxy, it reminds me of a bathtub drain. It
looks like everything is swirling and being drawn inwards. Does
everything in a galaxy eventually get sucked into the black hole? Or
are we too far away to ever be affected by the gravity of the black
hole at the center?

The range of the gravitational force is infinite, falling
off as the inverse square of the distance. So we here out
in the suburbs still feel its pull, but it's a greatly
reduced influence. The force that the Earth feels from the
central black hole is about one billionth that it feels from
the Sun.

The spiral arms of the galaxy are a geometric effect caused
by the finite speed of propagation of interactions through
the material comprising the body of the galaxy. Pressure
density waves take time to propagate, and the differential
rotation of the disk curves the apparent path. So things
like bursts of star formation triggered by shock waves tend
to form curved, spiral shapes.

We're not being sucked down a gravitational drain!


3) Then I have a question about the big bang. Is it true that
everything in the universe was compacted into something the size of
one atom? Did I really hear that right? If so, does it not follow
that every atom and molecule in my body, and your body, and was there
at the big bang? I mean, I can look at the fingernail on my little
pinky toe and consider that it was there at the big bang... and so
was Abraham Lincoln's hat... now that is cosmic!

Well, everything was all condensed into a superdense state
at the instant before the big bang, but you wouldn't be able
to recognize any individual molecules or atoms -- it was far
too hot for normal matter to exist. Even individual subatomic
particles could not exist stably at those temperatures. Think
of it more like a bowl of potential soup -- particle pairs
coming into and out of existence, constantly being generated and
annihilated. It wasn't until a time after the initial big bang
that the universe had cooled enough for individual particles to
have a chance to survive for any period. After essentially all
the matter particles mutually annihilated, we were left with a
bit of matter left over -- that makes up just about all of the
matter we can see in the universe today.

The universe had to expand and cool even more before the
remaining individual particles could get together and form
stable atoms, and these were almost entirely hydrogen and
helium, with just trace amounts of anything heavier. It
wasn't until after the first generations of stars had
produced the heavier elements via nucleosyntheses and
supernova explosions that the atoms you would recognize
as comprising you or Lincoln's hat were created.

solar bus driver wrote:
hello

I've been watching "The Universe" on the History Channel and I find
that show to be fascinating. I've learned so much from it but it also
generates questions. If anyone here can help me get clear on a few
things I'd really appreciate it. here are a couple things I've been
wondering about.

1) I'm particularly interested in the black hole at the center of our
galaxy... If there is a black hole at the center of our galaxy, is it
sucking in all the stars that are near the center? One of the episodes
stated that when a black hole "eats" a star it creates one of the
biggest events in the universe. So I'm looking at the center of our
galaxy and I see the closer you get the more stars there are, and if
there's black hole in the center, I'm thinking it must be gobbling up
stars constantly. Is that happening?

2) I'm also wondering, if there is a black hole in the center of the
galaxy, are we too far away to receive any of the gravitational pull?
When I look at the galaxy, it reminds me of a bathtub drain. It looks
like everything is swirling and being drawn inwards. Does everything
in a galaxy eventually get sucked into the black hole? Or are we too
far away to ever be affected by the gravity of the black hole at the
center?

3) Then I have a question about the big bang. Is it true that
everything in the universe was compacted into something the size of
one atom? Did I really hear that right? If so, does it not follow that
every atom and molecule in my body, and your body, and was there at
the big bang? I mean, I can look at the fingernail on my little pinky
toe and consider that it was there at the big bang... and so was
Abraham Lincoln's hat... now that is cosmic!

Any help on these issues is much appreciated!

Gary in Vermont
You were talking about the Black Hole at the center of our Galaxy, and I
ran across this from sci.space.news, and thought you'd find it
interesting. -- KL

Press and Public Relations Department
Max Planck Society for the Advancement of Science
Hofgartenstrasse 8
D-80539 Munich
Germany

Contact:

Dr. Mona Clerico, Press Officer
Max Planck Institute for Astrophysics
and
Max Planck Institute for Extraterrestrial Physics, Garching
Tel.: +49 89 30000-3980
Fax: +49 89 30000-3569

Dr. Stefanie Komossa
Max-Planck-Institute for Extraterrestrial Physics, Garching
Tel.: +49 89 30000-3577
Fax: +49 89 30000-3569

April 30th, 2008

News SP / 2008 (98)

Black hole expelled from its parent galaxy.

Max Planck Astronomers discover a gravitationally propelled mass monster.

By an enormous burst of gravitational waves that accompanies the merger
of two black holes the newly formed black hole was ejected from its
galaxy. This extreme ejection event, which had been predicted by
theorists, has now been observed in nature for the first time. The team
led by Stefanie Komossa from the Max Planck Institute for
extraterrestrial Physics (MPE) have thereby opened a new window into
observational astrophysics. The discovery will have far-reaching
consequences for our understanding of galaxy formation and evolution in
the early Universe, and also provides observational confirmation of a
key prediction from the General Theory of Relativity (Astrophysical
Journal Letters, May 10, 2008).

When two black holes merge, waves of gravitational radiation ripple
outward through the galaxy at the speed of light. Because the waves are
emitted mainly in one direction, the black hole itself is pushed in the
opposite direction, much like the recoil that accompanies the firing of
a rifle or the launching of a rocket. The black hole is booted from its
normal location in the nucleus of the galaxy. If the kick velocity is
high enough, the black hole can escape the galaxy completely.

The MPE team's discovery verifies, for the first time, that these
extreme events actually occur; up to now they had only been simulated in
supercomputers. The recoiling black hole caught the astrophysicists'
attention by its high speed -- 2650 km/s -- which was measured via the
broad emission lines of gas around the black hole. At this speed, one
could travel from New York to Los Angeles in just under two seconds.
Because of the tremendous power of the recoil the black hole, which has
a mass of several 100 millions solar masses, it was catapulted from the
core of its parent galaxy.

In addition to the emission lines from gas bound to the recoiling black
hole, the astronomers were also struck by a remarkably narrow set of
emission lines originating from gas left behind in the galaxy. This gas
has been excited by radiation from the recoiling black hole.

Gas that moves with the black hole -- the so-called accretion disk gas
-- continues to "feed" the recoiling black hole for millions of years.
In the process of being accreted, this gas shines in X-ray wavelengths.
In fact the team around Komossa also detected this X-ray emission from
the disk around the black hole at a distance of 10 billion light years:
by chance the region was scanned by the satellite ROSAT, and at the
extreme end of the visual field an X-ray source, the position
corresponding with the distant galaxy.

Large kicks for mergers

The new discovery is also important because it indirectly proves that
black holes do in fact merge and that the mergers are sometimes
accompanied by large kicks. This process had been postulated in theory,
but never before confirmed via direct observation. Another implication
of the discovery is that there must be galaxies without black holes in
their nuclei -- as well as black holes which float forever in space
between the galaxies.

This raises new questions for the scientists: Did galaxies and black
holes form and evolve jointly in the early Universe? Or was there a
population of galaxies which had been deprived of their central black
holes? And if so, how was the evolution of these galaxies different from
that of galaxies that retained their black holes?

In a close interplay between theory and observation, the astrophysicists
prepare to answer these questions. Various detectors on Earth and in
space, for example the space interferometer LISA, are set to track
gravitational waves. The MPE team's discovery will provide new impetus
for theorists to develop more detailed models of the superkicks and
their consequences for the evolution of black holes and galaxies.

Original work:

Komossa, S., Zhou, H., Lu, H.
A recoiling supermassive black hole in the quasar SDSSJ092712.65+294344.0?
Astrophysical Journal Letters, Vol. 678, L81, 2008 (May 10, 2008)

IMAGE CAPTION:
[http://www.mpg.de/bilderBerichteDoku.../Web_Zoom.jpeg
(737KB)]
Ejection from the nucleus: for the first time in nature, astronomers
have observed a supermassive black, which -- propelled by gravitational
waves - leaves its parent galaxy. The illustration depicts this scenario.
Image: MPE/HST-Archive