Stars · Observing · Physics
Parallax
Say it: PAIR-uh-laks IPA: /ˈpærəlæks/ noun
Parallax: A change in an object's apparent position caused by a change in the observer's viewpoint.
Hold a finger up and alternate which eye is open: it shifts against the background. Astronomers use the same geometric principle with a much larger observing baseline.
- Example
- The nearby star showed a measurable annual parallax against more distant stars.
- Why astronomers use it
- It provides a geometric method of estimating distance.
- Tiny cosmic connection
- A parallax shift comes from the changing viewpoint; a star's own motion is a separate effect to account for.
Observatory Stars Observing Physics
Where to check it
Written for Cool Moon Facts in its own words; the sources cover the same idea in more depth.