Not specifically on Arcturus, but I do have
relevant information. Our galaxy has two major
"populations" of stars, called "population I" and
"population II". (I guess the Calvin and Hobbes
cartoon was correct, scientists often use very
unimaginative names). These correspond to "disk"
and "halo" stars. Halo stars are distributed
spherically around the galaxy center, and their
orbits are fairly randomly distributed. Disk stars
orbit in the plane of the galactic disk. If you
pick at random some location in the galactic disk,
then all disk stars near that point will have
roughly the same velocity.
But there are a
few nearby halo stars. These have large velocities
in almost any direction (relative to our sun),
whereas nearby disk stars have small
So perhaps you could try to find
out if Arcturus is a population II star. There
are other differences between Population I and II
stars. A great general astronomy reference is
Frank Shu's "The Physical Universe".
Well, I looked around but I couldn't find anything
that seemed overly unusual about the magnitude of
Arcturus' motion.Arcturus is a pretty close by
(about 36 light years) red giant making it pretty
bright. It also has a pretty large motion on the
sky, but Barnard's star moves more and Sirius
seemed to move in the same general direction. On
the other hand, after talking to another answer,
it turns out that Arcturus is a star that is from
the galactic halo and passing through the disk of
the galaxy near us. So it is not moving in the
same general way as other stars that like the Sun
are in the
galactic disk. Arcturus is also
almost as close to us now as it's ever going to be.
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