Why Are There Galaxies?

They make space clumpy. They seem to have been created and shaped a long
time ago. They could be a big argument against a "single" big bang.
Stars come out of clouds,and that means these was not one big cloud. If
blackholes are at the core of galaxies they must have developed there
first. Why do astronomers tell us stars are forming in the outer fringe
of the galaxies? What makes that the rule in this spacetime? Seems star
making has slowed down by a million % Never heard of a new galaxy
forming. Well this is another mystery. The forming of galaxies. Bert

G=EMC^2 Glazier wrote:
They make space clumpy. They seem to have been created and shaped a
long time ago. They could be a big argument against a "single" big
bang. Stars come out of clouds,and that means these was not one big
cloud. If blackholes are at the core of galaxies they must have
developed there first. Why do astronomers tell us stars are forming
in the outer fringe of the galaxies? What makes that the rule in this
spacetime? Seems star making has slowed down by a million % Never
heard of a new galaxy forming. Well this is another mystery. The
forming of galaxies. Bert

Apparently ('cos I wasn't there) the Big Bang wasn't completely unifom so
eventually matter clumped together in places.
That's not a particularly scientific answer, but I think it's more or less
the case. :-)

Steve

--
www.frontierastro.co.uk

FrontierAstro - dedicated to Frontier and Astronomy

Would like to add some questions on spiral galaxies centers. Is the
blackhole creating such great radiation we observe in the hub?
Can there be more than one blackhole there? We now know
closer to our galaxies core there is a star that radiates 10 million
times that of the sun.(brightest star in the Milky Way) Is
it a supernova?. Thats a little to close for comfort. One could write a
Sci-fiction book,and use that as the theme. This is my most important
question. We can't see across to our galaxy's hub,for space dust blocks
out its view. Here comes my question. How would this effect our night
sky if there was no dust? Bert

"G=EMC^2 Glazier" wrote in message...
...

. . . This is my most important
question. We can't see across to our galaxy's hub,for space dust blocks
out its view. Here comes my question. How would this effect our night
sky if there was no dust? Bert

I've oftened wondered about this myself, Bert. The hub of
the Milky Way Galaxy is probably very luminous. If there
were no dust to block this brightness, it would probably
appear very beautiful indeed!

And there might not be much deep-sky viewing from the
surface of Earth except during winter.

Here's an infrared shot...

http://www.seds.org/messier/more/mw_cobe.html

NASA assures us that we could read a newspaper by
the light of the unobstructed galaxy center. But i wonder...

If we also somehow remove the stars in the spiral arm
that is between us and the center, the stars that make up
the band called the Milky Way, there are so many very
bright stars in the center of the Galaxy that i truly believe
the night would only exist for us when the center is on the
same side of Earth as the Sun.

During the summer we would have constant day-like
brightness, and only winter would bring the beauty of the
night sky back to us.

And i also wonder if the dust *completely* surrounds the
center? IOW, will there come a time in the Sun's orbit
around the center when the dust thins and we can see
all those beautiful central stars?

Unfortunately, it takes the Sun between 200,000,000 and
250,000,000 years to make a full orbit around the center.
So it may be awhile before we find out. sigh

happy days and...
starry starry nights!

--
"Oh give me please the Universe keys
That unlock all those mysteries!"
You pay your fees, you find some keys,
That keeps you always groping.

"Oh give me please the Happiness keys
That ease the pain of biting fleas!"
Today you seize you need no keys,
That door is always open.

Paine Ellsworth

In message
, Painius
writes
"G=EMC^2 Glazier" wrote in message...
...

. . . This is my most important
question. We can't see across to our galaxy's hub,for space dust blocks
out its view. Here comes my question. How would this effect our night
sky if there was no dust? Bert

I've oftened wondered about this myself, Bert. The hub of
the Milky Way Galaxy is probably very luminous. If there
were no dust to block this brightness, it would probably
appear very beautiful indeed!

And there might not be much deep-sky viewing from the
surface of Earth except during winter.

Here's an infrared shot...

http://www.seds.org/messier/more/mw_cobe.html

NASA assures us that we could read a newspaper by
the light of the unobstructed galaxy center. But i wonder...

If we also somehow remove the stars in the spiral arm
that is between us and the center, the stars that make up
the band called the Milky Way, there are so many very
bright stars in the center of the Galaxy that i truly believe
the night would only exist for us when the center is on the
same side of Earth as the Sun.

The problem with this idea is that the centre of the galaxy is still
10,000 parsecs away. The absolute magnitude of the galaxy is -20. Put it
10,000 times further away and its brightness drops by 100 million, which
is about 20 magnitudes.
I'm fairly sure there's something wrong with that calculation because
globular clusters have a median absolute magnitude of -8.4, and the
bright ones have an apparent magnitude of 3 to 8. So the galaxy as a
whole should be about as bright as Venus; some negative magnitude. So it
would be an incredibly spectacular sight, but certainly not dazzling.
--
Rabbit arithmetic - 1 plus 1 equals 10
Remove spam and invalid from address to reply.

Hi there Panius. You posted:

I've oftened wondered about this myself, Bert. The hub of
the Milky Way Galaxy is probably very luminous. If there
were no dust to block this brightness, it would probably
appear very beautiful indeed!

It is beautiful, and if it weren't for all the light pollution, more people on
this planet would get a good chance to see at least the outer sections of the
bulge of the galaxy. From a dark sky site during the summer, the faint
glowing dome of the nuclear bulge is visible well out into the constellations
of Scorpius and Ophiuchus. In fact, at a site like that of the Nebraska Star
Party, the galaxy produces enough light to allow objects to cast very faint
shadows. We can't see the very core due to the intervening dust lanes, but
the area in the direction of the galactic center is quite rich in objects and
detail, especially in binoculars or a richest-field telescope.

And there might not be much deep-sky viewing from the
surface of Earth except during winter.

Well, the core region is around 26,000 light years away, so while it would be
bright, I doubt it would be bright enough to completely extinguish deep-sky
viewing.

If we also somehow remove the stars in the spiral arm
that is between us and the center, the stars that make up
the band called the Milky Way, there are so many very
bright stars in the center of the Galaxy that i truly believe
the night would only exist for us when the center is on the
same side of Earth as the Sun.

I think the distance factor would make this unlikely. For a comparison
example, the bright nuclear bulge/core region of the Andromeda galaxy is
visible to us almost unobscured, and the bulge's total integrated brightness
is roughly equivalent to that of a 5th magnitude star. If we somehow moved it
from its current distance of about 2.4 million light years to a distance of
only 26,000 light years, its total magnitude would be about magnitude -4.8,
which is similar to that of Venus near its brightest. The Andromeda Galaxy is
a bit bigger galaxy than our own Milky Way, so our core might not even appear
quite at that brightness level. The glow would also not be concentrated at a
point but rather diffuse, so the overall lighting effect would be somewhat
diminished.

And i also wonder if the dust *completely* surrounds the
center? IOW, will there come a time in the Sun's orbit
around the center when the dust thins and we can see
all those beautiful central stars?

The dust doesn't necessarily surround the center, but is mostly in a series of
irregular lanes which are interwoven with the spiral arms. We will never see
the core itself visually from our solar system because there will always be at
least a couple of spiral arms with their immense dust lanes between us and the
core. In the infrared and radio wavelengths, we can see the very center, but
in visible light, the extinction caused by the dust is simply too great.
Clear skies to you.
--
David W. Knisely
Prairie Astronomy Club: http://www.prairieastronomyclub.org
Hyde Memorial Observatory: http://www.hydeobservatory.info/

**********************************************
* Attend the 11th Annual NEBRASKA STAR PARTY *
* July 18-23, 2004, Merritt Reservoir *
* http://www.NebraskaStarParty.org *
**********************************************

Jonathan Silverlight wrote:

The problem with this idea is that the centre of the galaxy is still 10,000 parsecs away.

Well, that is a little on the high side. Current best estimates based on the
radio parallax of the galactic core (Sagittarius A*) yield a distance of
around 8,000 parsecs +/-500 pc. However, you are correct that the core would
probably have an integrated brightness similar to that of Venus near its
brightest if we could see the core unobscured. Clear skies to you.
--
David W. Knisely
Prairie Astronomy Club: http://www.prairieastronomyclub.org
Hyde Memorial Observatory: http://www.hydeobservatory.info/

**********************************************
* Attend the 11th Annual NEBRASKA STAR PARTY *
* July 18-23, 2004, Merritt Reservoir *
* http://www.NebraskaStarParty.org *
**********************************************

Hi Painius. Well I can always count on you to create great interest to
my posts. That was a great picture. Is it realy a picture of our galaxy?
Painius I would not mind waiting that 200,000 years to get to are other
side of the hub. Its my great curiosity. My proplem is " My life is
going into the twilight zone" and that could be what the night sky would
be like if the bright stars (100millions of them) of the hub could come
shinning through. Bert

All Very nice answers. Interesting we have stars in our line of view
blocking as well. The sun is way out in left field)(or is it right
field) We can see other far away galaxy hubs millions of LY away better
than our own hub and that is only 28,000 LY away Still this does
not answer my first question. Why are there galaxies? Bert

"G=EMC^2 Glazier" wrote in message
...
All Very nice answers. Interesting we have stars in our line of view
blocking as well. The sun is way out in left field)(or is it right
field) We can see other far away galaxy hubs millions of LY away better
than our own hub and that is only 28,000 LY away Still this does
not answer my first question. Why are there galaxies? Bert

Why are there galaxies?
because at the early stages of the universe, small local densities acted as
centres of gravity, so that they acted as nucleii for condensation of mass.

Remember, in a completely uniform universe, the density remains uniform. BUT
any departure from uniformity acts to destroy uniformity.

So the universe tended towards clumpiness, and galaxies formed in clusters.