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  2. Light-year - Wikipedia

    en.wikipedia.org/wiki/Light-year

    A contemporary German popular astronomical book also noticed that light-year is an odd name. [25] In 1868 an English journal labelled the light-year as a unit used by the Germans. [26] Eddington called the light-year an inconvenient and irrelevant unit, which had sometimes crept from popular use into technical investigations. [27]

  3. Astronomical unit - Wikipedia

    en.wikipedia.org/wiki/Astronomical_unit

    Distance light travels in one day — Light-year: 63 241 — Distance light travels in one Julian year (365.25 days) — Oort cloud: 75 000: ± 25 000: Distance of the outer limit of Oort cloud from the Sun (estimated, corresponds to 1.2 light-years) — Parsec: 206 265 — One parsec. The parsec is defined in terms of the astronomical unit, is ...

  4. Speed of light - Wikipedia

    en.wikipedia.org/wiki/Speed_of_Light

    A light-year is the distance light travels in one Julian year, around 9461 billion kilometres, 5879 billion miles, or 0.3066 parsecs. In round figures, a light year is nearly 10 trillion kilometres or nearly 6 trillion miles. Proxima Centauri, the closest star to Earth after the Sun, is around 4.2 light-years away. [89]

  5. Astronomical system of units - Wikipedia

    en.wikipedia.org/wiki/Astronomical_system_of_units

    An equivalent formulation of the old definition of the astronomical unit is the radius of an unperturbed circular Newtonian orbit about the Sun of a particle having infinitesimal mass, moving with a mean motion of 0.017 202 098 95 radians per day. [5] The speed of light in IAU is the defined value c 0 = 299 792 458 m/s of the SI units.

  6. Glossary of astronomy - Wikipedia

    en.wikipedia.org/wiki/Glossary_of_astronomy

    The Milky Way Galaxy has a diameter of 100,000–200,000 light-years and is estimated to contain 100–400 billion stars and at least that number of planets. The Solar System is located on the inner edge of one of the Milky Way's spiral arms, about 27,000 light-years from the Galactic Center, which the Sun orbits with a period of 240 million ...

  7. Universe - Wikipedia

    en.wikipedia.org/wiki/Universe

    Although the distance traveled by light from the edge of the observable universe is close to the age of the universe times the speed of light, 13.8 billion light-years (4.2 × 10 ^ 9 pc), the proper distance is larger because the edge of the observable universe and the Earth have since moved further apart.

  8. AOL Mail

    mail.aol.com

    Get AOL Mail for FREE! Manage your email like never before with travel, photo & document views. Personalize your inbox with themes & tabs. You've Got Mail!

  9. Unit of time - Wikipedia

    en.wikipedia.org/wiki/Unit_of_time

    About 31,709 years. megaannum: 10 6 yr: Also called "megayear". 1000 millennia (plural of millennium), or 1 million years (in geology, abbreviated as Ma). petasecond: 10 15 s: About 31 709 791 years. galactic year: 2.3 × 10 8 yr: The amount of time it takes the Solar System to orbit the center of the Milky Way Galaxy (approx 230 000 000 years ...