# How can you find the parallax angle of a star?

##### 1 Answer

See the explanation.

#### Explanation:

With respect to a star, the Earth E turns around its star Sun along

half of its nearly-circular orbit, of radius 1 AU, in one half year..

The diameter ( of length 2 AU ) of the Earth's orbit joining these

two positions P and Q subtends the so-called

parallax

Easily, the distance of the star ES, in AU unit, is given by

As

In the case of the Sun,

should be retained as such, and the distance reasd

ES = cot(alpha.2) AU = 1 AU.

So,

of the Earth's orbit.

Note that all these results are for half-year spacing PQ = 2AU,.