Definition

1. Noun:
   • A unit of astronomical distance: A parsec is a unit of length used to measure vast distances between astronomical objects outside the Solar System. It is defined as the distance from the Sun (or Earth) at which one astronomical unit subtends an angle of one arcsecond. It is equivalent to approximately 3.26 light-years.

Usage

• The parsec is a standard unit in astronomy and astrophysics for expressing distances to stars and galaxies.
• It is primarily used in professional and scientific contexts rather than everyday conversation.

Examples

• Noun:
  • The star Proxima Centauri is about 1.3 parsecs from Earth.
  • Astronomers measured the galaxy to be over a million parsecs away.

Advanced Usage

• "Kiloparsec (kpc)": A unit equal to one thousand parsecs, commonly used for distances within a galaxy.
  • The Milky Way's diameter is roughly 30 kiloparsecs.
• "Megaparsec (Mpc)": A unit equal to one million parsecs, used for distances between galaxies.
  • The galaxy cluster is located several hundred megaparsecs from us.

Variants and Related Words

• Parallax second: Another name for a parsec, stemming from its definition based on stellar parallax.
• Light-year: A related unit of astronomical distance; one parsec equals about 3.26 light-years.

Synonyms

• Astronomical unit of distance: A general synonym, though less precise.
• (Abbreviation) pc: The standard abbreviation for parsec.

Notes

• The term is a portmanteau of "parallax" and "arcsecond."
• It is a fixed, standardized unit, not a phrasal verb or idiom.

Noun

1. a unit of astronomical length based on the distance from Earth at which stellar parallax is 1 second of arc; equivalent to 3.262 light years