gen-define-stellar-parallax-and-give-one-short-worked-example-3164

Define stellar parallax and give one short worked example.

# Stellar Parallax **Definition:** Stellar parallax is the apparent shift in position of a nearby star against the background of distant stars as observed from opposite sides of Earth's orbit around the Sun. It's measured as half the total angular shift (the parallax angle, *p*) and is used to determine stellar distances. ## Relationship: The distance to a star in **parsecs** is: **d = 1/p** where *p* is the parallax angle in arcseconds. --- ## Worked Example **Problem:** A star has a measured parallax angle of 0.25 arcseconds. What is its distance from Earth? **Solution:** - Given: p = 0.25 arcseconds - Using d = 1/p - d = 1/0.25 = **4 parsecs** Converting to light-years (1 parsec = 3.26 light-years): - d = 4 × 3.26 = **13.04 light-years** **Answer:** The star is 4 parsecs or approximately 13 light-years away. --- *Note: Only relatively nearby stars have measurable parallax. The largest parallax is Proxima Centauri at ~0.77 arcseconds (distance: 1.3 parsecs or 4.2 light-years).*