Why Are There Galaxies?

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/

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* Attend the 11th Annual NEBRASKA STAR PARTY *
* July 18-23, 2004, Merritt Reservoir *
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