Parallax Calculator
Calculate distance to stars from parallax angle and baseline using trigonometric parallax formulas in astronomy.
Measuring Distance with Parallax
Parallax is the apparent shift of a nearby object against a distant background when the observer changes position. Astronomers use stellar parallax to estimate distances to nearby stars.
Stellar Parallax Formula
$$d\ (\text{pc}) = \frac{1}{p\ (\text{arcsec})}$$One parsec is defined as the distance at which one astronomical unit subtends one arcsecond of parallax.
Baseline Parallax Formula
$$d = \frac{b}{2 \tan(p/2)}$$Here \(b\) is the baseline between observation points and \(p\) is the parallax angle. This form is useful for surveying and short-baseline geometry.
Related tools: Astronomical Converter and Hubble's Law Calculator.
Frequently Asked Questions
What is a parsec in everyday terms?
One parsec is about 3.26 light-years, or roughly 30.9 trillion kilometers.
Why must parallax angle be in arcseconds for d = 1/p?
That definition is built into the parsec unit. Convert degrees or arcminutes to arcseconds first if needed.
What baseline does stellar parallax use?
Earth's orbit provides about 2 AU baseline between observations six months apart.
When should I use the baseline formula?
Use it when you know a physical baseline and measured parallax angle in a local geometry problem.
Can parallax measure very distant galaxies?
Stellar parallax works for relatively nearby stars. Extremely distant objects need other distance indicators.
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