Parallax

Definition

Parallax is the apparent shift in the position of an object when viewed from two different vantage points. In astronomy, it is used to measure distances to nearby stars based on their apparent movement against distant background stars as Earth orbits the Sun.

5 Must Know Facts For Your Next Test

1. Parallax was first used by ancient Greek astronomers to estimate the distance of celestial objects.
2. The parallax angle decreases as the distance to a star increases, making it difficult to measure very distant stars.
3. Astronomical units (AU) and parsecs are commonly used units when calculating distances using parallax.
4. The baseline for measuring stellar parallax is typically the diameter of Earth's orbit around the Sun, approximately 2 AU.
5. Modern instruments like the Gaia spacecraft have significantly improved our ability to measure stellar parallaxes accurately.

Review Questions

• What is parallax and how is it used in astronomy?
• Why does the parallax angle become smaller with increasing distance?
• What baseline is typically used for measuring stellar parallax?

Related terms

Astronomical Unit (AU): The average distance between Earth and the Sun, approximately 149.6 million kilometers.

Parsec:

A unit of distance used in astronomy equal to about 3.26 light-years or approximately 31 trillion kilometers.

Stellar Parallax:

The small angular shift observed in a star's position due to Earth's orbit around the Sun, used to determine stellar distances.