# How does one calculate the parallax of stars?

##### 1 Answer

See explanation

#### Explanation:

If S is a star observed from E, at an angle

horizontal and the same star is observed again, after half a year,

at

the parallax

The distance of the star is now approximated as

Note that the distance across, between the two positions of E, is

nearly the diameter of [the Earth](https://socratic.org/astronomy/our-

solar-system/the-earth)'s orbit =

as p is small,

ES = 1/p AU, nearly.

Vice versa, we can predict this p for the half year interval, if the

distance of the star is already known.

For example, the nearest S Proxima Centauri is at a distance ES =

4.246 ly, and this gives

Half year parallax