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    Astronomy Units: Light Years and Parsecs

    UnitConvertLab Team
    2026-07-20
    6 min read

    The Light Year (ly)

    A light year is the distance light travels in a vacuum in one year.

    • Speed of Light: ~300,000 km/s
    • 1 Light Year: ~9.46 trillion kilometers (5.88 trillion miles)

    The Astronomical Unit (AU)

    Used for distances within our solar system. It's the average distance from the Earth to the Sun.

    • 1 AU ≈ 150 million kilometers

    The Parsec (pc)

    Short for "parallax second." This is the preferred unit for professional astronomers.

    • 1 Parsec ≈ 3.26 Light Years

    Key Takeaways

    • Proxima Centauri (nearest star) is 4.2 ly away
    • The Milky Way is about 100,000 ly across
    • The observable universe is 93 billion ly across

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