What is proper motion and what are arcseconds?

I have to do a project about Barnard's star and apparently it's proper motion is measured to be 10.3 arcseconds per year. I don't understand the concept of proper motion and how it is measured.What is proper motion and what are arcseconds?Arc seconds are an angular measure. The circle is divided into 360 degrees. Each degree is divided into 60 minutes. Each minute is divided into 60 seconds (or arc seconds). So 1 arc second = 1/3600 of a degree.



Proper motion is the motion in the sky (the angle) in a particular coordinate system. This says that the angle you point your telescope to see the star is different by 10.3 arc seconds every year.



http://en.wikipedia.org/wiki/Proper_moti鈥?/a>What is proper motion and what are arcseconds?Arcseconds are a unit of angle. Very tiny angle. A 3600th of a degree. The moon's diameter in the sky is roughly 1800 arcseconds.


Proper motion is a measure of how the celestial coordinates of finding a star vary as time progresses. The stars seem to be on fixed positions relative to one another, and relative to the general backdrop of space...BUT...this isn't 100% the case. They only do so because they are so far away.


Proper motion is where we precisely measure how the directions to the stars shift from the "fixed" backdrop coordinate system of space as time progresses. Barnard's runaway star is the record holder for this.



"As well, does Barnard's Star orbit the Sun??"

No, there isn't a single star that orbits the sun. At least not that we know of.


There was a nemesis hypothesis of the sun having a dark unseen stellar companion (possibly a brown dwarf), that we name nemesis, but that idea is a bit obsolete.


The proper motion of Barnard's star doesn't even match what it needs to be to correspond to a gravity-alone orbit about the sun.
After a distance of 1 light year from the sun, gravity of other stars begins to take over.What is proper motion and what are arcseconds?PROPER MOTION - The actual movement of a star relative to your location. Don't confuse proper motion with the *apparent* motion of a star which is due to Earth's rotation.



ARCSECONDS - A measure of angular separation, similar to degrees, minutes and seconds - one sixtieth of an arc minute. (1/3600th of a degree.)