The star Procyon has a parallax of 0.287 arcsec and a proper motion of 1.25 arcsec per year. What is the tangential velocity of Procyon?

Question

Quizplus · Accepted Answer

To find tangential velocity, we use the formula:
vtangential = 4.74 × proper motion × distance
where proper motion is in seconds of arc per year and distance is in parsecs.
distance = 1/parallax = 1/(0.287 arcsec) ≈ 3.48 pc
vtangential = 4.74 × 1.25 arcsec/year × 3.48 pc = 20.6 km/s ≈ 21 km/s (rounded to the nearest km/s)

The Star Procyon Has a Parallax of 0