Parsec

Parsec

A parsec (symbol: pc) is a unit of length used to measure large distances to astronomical objects outside the Solar System. A parsec is approximately equal to 3.26 light-years (31 trillion kilometres or 19 trillion miles) in length. The name "parsec" is derived from the distance at which one astronomical unit subtends an angle of one arcsecond, a measurement known as "parallax second".

History

The concept of the parsec was first introduced in 1913 by the British astronomer Frank Watson Dyson, as a convenient unit of measure in astrometry, the precise measurement of the positions and movements of celestial bodies. The parsec is still widely used in astrometry today.

Calculation

The distance corresponding to a parallax angle of one arcsecond is defined as one parsec. This can be calculated using the formula:

d = 1/p

where d is the distance in parsecs and p is the parallax angle in arcseconds. This formula is derived from the definition of the astronomical unit, which is the mean distance from the Earth to the Sun.

Usage

The parsec is commonly used in astronomy to measure distances between stars and galaxies. For example, the Andromeda Galaxy is approximately 780 kiloparsecs (2.5 million light-years) from the Earth.

See also

• Astronomical unit
• Light-year
• Astronomy
• Astrophysics