Stellar Parallax Calculator
Distance in parsecs is one over the parallax. No constant.
Work out Stellar Parallax. Distance in parsecs is one over the parallax. No constant. Names the misconception directly.
Distance
1.3012 pc
4.2441 light years · Very close — measurable from the ground with ease
Distance in parsecs is simply 1 divided by the parallax in arcseconds. There is no constant because the parsec is defined to make it so — it is the distance at which one astronomical unit subtends one arcsecond. Parallax is the only direct distance measurement in astronomy: the apparent shift of a nearby star against the background as the Earth moves across its orbit. Everything further is calibrated against it, which makes it the bottom rung of the entire cosmic distance ladder. No star is close enough to have a parallax of a full arcsecond — the nearest, Proxima Centauri, manages 0.77. Gaia has pushed reliable measurement down to around 20 microarcseconds, which reaches a good fraction of the galaxy, and beyond that other methods take over.
How the Stellar Parallax Calculator works
Distance from parallax, in parsecs, light years and astronomical units. The parsec is defined so this relation has no constant at all — it is the distance at which one AU subtends one arcsecond.
Also known as: distance to a star from parallax · parsecs to light years · how far is proxima centauri · how do we measure star distances
Frequently asked questions
How do you calculate distance from parallax?
Distance in parsecs is 1 divided by the parallax in arcseconds. There is no constant, because the parsec was defined to make it so.
What is a parsec?
The distance at which one astronomical unit subtends one arcsecond — about 3.26 light years. The name is a contraction of "parallax second".
Which star has the largest parallax?
Proxima Centauri, at 0.77 arcseconds. Nothing is close enough to reach a full arcsecond, which is why every real parallax is a fraction of one.
How far can parallax measure?
Gaia has pushed reliable measurement to around 20 microarcseconds, reaching a good fraction of the galaxy. Beyond that, uncertainties dominate and other methods — Cepheid variables, supernovae — take over.
Why does parallax matter so much?
It is the only direct distance measurement in astronomy, based on geometry alone with no assumptions about the object. Everything further is calibrated against it, which makes it the bottom rung of the cosmic distance ladder.
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