Distance

Definition

Distance in astronomy is the measure of space between two celestial objects. It is often expressed in units like light-years, parsecs, or astronomical units (AU).

5 Must Know Facts For Your Next Test

1. 1 light-year is the distance light travels in one year, approximately 9.46 trillion kilometers.
2. A parsec is equivalent to about 3.26 light-years and is based on the parallax angle of one arcsecond.
3. The astronomical unit (AU) represents the average distance between Earth and the Sun, roughly 149.6 million kilometers.
4. Parallax method involves measuring the apparent shift of a star against distant background objects as observed from different positions along Earth's orbit.
5. Redshift and standard candles (like Cepheid variables) are methods used for determining distances to far-off galaxies.

Review Questions

• What is the approximate value of one astronomical unit (AU) in kilometers?
• How does a parsec compare to a light-year?
• What method uses the apparent shift in position of a star to determine its distance?

Related terms

Light-Year:

The distance that light travels in one year, approximately 9.46 trillion kilometers.

Parsec:

A unit of distance equal to about 3.26 light-years, derived from parallax measurements.

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