Subtracting the proper motion resulting from movement of the Sun

In summary, The person is trying to calculate the velocity of a star with respect to its local medium using proper motion measurements. They have found a method to calculate corresponding velocities but it is with respect to the Sun. They have been searching for a way to compute the velocity with respect to the local standard of rest and have found a guide in Astronomy and Astrophysics (v.431, p.L1-L4, 2005). They have not been able to find a clear guide and are asking for help.
  • #1
rawen
6
0
Hello,
I have been trying to compute the velocity of the star with respect to its local medium from the proper motion measurements. Sure, you can calculate the corresponding velocities by v = 4.74*(proper motion)*distance (in suitable units), but this resulting velocity is now with respect to Sun.

I have been searching for a method to compute that. So far I have found the velocity components of the solar peculiar motion (U, V, W) = (10, 11, 7.2) km/s and velocity of the local standard of rest v_lsr = 240 km/s. I have tried to convert the proper motion (in galactic coordinates) into velocity in cartesian coordinates, then subtract the solar velocity given as (10, 11 - 240, 7.2) and convert the resulting velocity back into galactic coordinates but I keep getting the wrong values...

I must be doing something wrong. I have not been able to found any comprehensible guide on how to do this. If someone know of something that can help me, I will be grateful.
 
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  • #2
A brief cookbook can be found in Astronomy and Astrophysics, v.431, p.L1-L4 (2005) .
Just in a case someone might need it sometime :).
 

Related to Subtracting the proper motion resulting from movement of the Sun

1. What is proper motion?

Proper motion is the apparent motion of a star on the celestial sphere, caused by its actual motion through space. It is measured in units of arcseconds per year.

2. How does the Sun's movement affect the proper motion of stars?

The Sun's movement affects the proper motion of stars because it is also moving through space. This causes a relative motion between the Sun and the stars, resulting in a proper motion that needs to be subtracted in order to accurately measure the stars' true motion.

3. Can proper motion be observed from Earth?

Yes, proper motion can be observed from Earth. However, it is a very small angular displacement and can only be measured accurately over long periods of time.

4. What is the purpose of subtracting the Sun's proper motion from star measurements?

The purpose of subtracting the Sun's proper motion from star measurements is to correct for the relative motion between the Sun and the stars. This allows for a more accurate measurement of the stars' true motion through space.

5. How is the Sun's proper motion calculated and subtracted from star measurements?

The Sun's proper motion is calculated by observing its motion relative to other celestial objects over a long period of time. This value is then subtracted from the measured proper motion of stars to account for the Sun's movement.

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