How to Calculate Stellar Parallax
What is Stellar Parallax?
Parallax measures nearby star distance by observing angular shift as Earth orbits Sun. 1 arcsecond parallax = 1 parsec distance.
Formula
Calculate distance: d (pc) = 1 / parallax (arcsec)
Step-by-Step Guide
- 1Measure apparent position change (arcseconds) from opposite Earth orbits
- 2Calculate distance: d (pc) = 1 / parallax (arcsec)
- 3Verify with other methods
Worked Examples
Input
Parallax = 0.1 arcsec (Proxima Centauri)
Result
d = 10 pc ≈ 3.26 light-years
Nearest star
Common Mistakes to Avoid
- ✕Confusing parsec with light-year
- ✕Over-interpreting parallax errors for distant objects
Frequently Asked Questions
Why is parallax hard to measure?
Shift is tiny even for nearby stars; requires precision astrometry.
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