Parallax Distance Formula
Calculate the distance to nearby stars using the parallax angle.
The most direct method for measuring stellar distances.
The Formula
d = 1 / p
The parallax formula converts a star's apparent angular shift into its distance. As Earth orbits the Sun, nearby stars appear to shift slightly against distant background stars.
Variables
| Symbol | Meaning |
|---|---|
| d | Distance to the star (parsecs) |
| p | Parallax angle (arcseconds) |
Note: 1 parsec = 3.262 light-years = 3.086 × 10¹⁶ meters.
Example 1
Proxima Centauri has a parallax of 0.7687 arcseconds
d = 1 / 0.7687
d ≈ 1.301 parsecs ≈ 4.24 light-years
Example 2
A star has a parallax of 0.01 arcseconds
d = 1 / 0.01
d = 100 parsecs ≈ 326 light-years
When to Use It
Use the parallax distance formula when:
- Measuring the distance to relatively nearby stars (within about 1,000 parsecs)
- Converting parallax measurements from telescopes into real distances
- Calibrating other distance measurement methods
- Building the cosmic distance ladder