Parsec

Definition

A parsec is a unit of distance used in astronomy, equivalent to about 3.26 light-years or 31 trillion kilometers. It represents the distance at which one astronomical unit subtends an angle of one arcsecond.

5 Must Know Facts For Your Next Test

1. 1 parsec is approximately equal to 3.26 light-years.
2. The term 'parsec' is derived from 'parallax of one arcsecond'.
3. Parsecs are commonly used to measure distances to stars and galaxies outside our solar system.
4. The measurement relies on observing the apparent shift in position (parallax) of a star against more distant background objects as Earth orbits the Sun.
5. Calculating distances in parsecs helps astronomers understand the scale and structure of the universe.

Review Questions

• How many light-years are there in one parsec?
• What does the term 'parsec' stand for?
• Why do astronomers use parsecs instead of astronomical units for measuring large distances?

Related terms

Light-Year: A unit of astronomical distance equivalent to the distance that light travels in one year, roughly 9.46 trillion kilometers.

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

Parallax: The apparent shift in position of a nearby object against a distant background due to a change in observer's viewpoint.