Question

If Kapteyn's star has a parallax angle of 0.255 arcsec, a proper motion of 8.67 arcsecs per year and a radial velocity of +246 km/s, What is the star's tangential velocity?

Answer 1

`v_t=183.0dot(3)km` `s^(-1)`

Explanation:

`v_t` is given by the formula: `v_t=(4.75mu)/p`, where:

• `mu` = proper motion (arc seconds per year)
• `p` = parallax (arc seconds)

`v_t=(4.75*8.67)/0.225=183.0333...=183.0dot(3)km` `s^(-1)`