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How does a liquid mirror telescope work?

Response #: 1 of 1
Author: samuel p bowen
The simplest idea is to rotate a liquid about the central axis and let its
shape change under the rotation. This can give you a shape that could focus
a light ray. The surface would be clean and have no impurities.

What do astronomers use to figure out if an object is a star, planet,
asteroid or comet?

Response #: 1 of 1
Author: asmith
If you just look at an object in the sky once, it could be hard to tell
anything much about them (although astronomers do have techniques called
“spectroscopy” that tell something about what an object is made of). But if
you watch the object for a while, you can see where it is going, trace out
its orbit, see what influence it has on its neighbors, etc., which tells you
much about it: stars hardly move at all; planets move in pretty ordinary
close-to-circular orbits about the sun, while other things can be seen to
orbit around them (which then tells us how massive those planets are) and
asteroids tend to be clustered in the asteroid belt or else to have kind of
elongated orbits, and comets have really wild orbits, and in particular tend
to get close to the sun where they flare up and get bright every once in a while.

What is the distance between the center of the Milky Way and our Sun?

Response #: 1 of 1
Author: hawley
The Milky Way has a radius of about 15 kpc, and the Sun is about 10 kpc from
the center. A “kpc” is a kilo-parsec. One parsec is 3.26 light years or
3.086 x 10^18 cm. I leave the awesome mathematical challenge of converting
to miles (or kilometers) as an exercise for the reader.

Does the Sun have any motion in respect to our solar system, or is it
completely stationary (no spin, etc.) with all of the other planets orbiting
around it?

Response #: 1 of 2
Author: hawley
The Sun not only spins on its axis but also travels around the center of our
galaxy in a big orbit. And our galaxy is moving relative to other galaxies.
Basically, everything is moving.

Response #: 2 of 2
Author: rcwinther
If we neglect the motion of our solar system as a whole, then all of the
bodies in the solar system revolve around the center of mass of the solar
system. The center of mass is an imaginary point that is determined by a
sort of averaging over the whole. The solar system’s center of mass lies
deep within the Sun (because the Sun contains the vast majority of the solar
system’s mass) but not at its center. Hence, the Sun also revolves about
this point; we say that it wobbles (in our case, almost entirely due to
Jupiter’s pull on the Sun). At the moment, looking for this sort of wobble
in other stars is our best bet for inferring the existence of planetary
systems around those stars.

More here : http://www.newton.dep.anl.gov/askasci/astron98.htm