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  2. Light-year - Wikipedia

    en.wikipedia.org/wiki/Light-year

    The most distant space probe, Voyager 1, was about 18 light-hours (130 au,19.4 billion km, 12.1 billion mi) away from the Earth as of October 2014. [29] It will take about 17 500 years to reach one light-year at its current speed of about 17 km/s (38 000 mph, 61 200 km/h) relative to the Sun.

  3. 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]

  4. Proper motion - Wikipedia

    en.wikipedia.org/wiki/Proper_motion

    A proper motion of 1 arcsec per year 1 light-year away corresponds to a relative transverse speed of 1.45 km/s. Barnard's Star's transverse speed is 90 km/s and its radial velocity is 111 km/s (perpendicular (at a right, 90° angle), which gives a true or "space" motion of 142 km/s.

  5. List of common astronomy symbols - Wikipedia

    en.wikipedia.org/wiki/List_of_common_astronomy...

    d - in km = kilometer; d - in mi = mile; d - in AU = astronomical unit; d - in ly = light-year; d - in pc = parsec; d - in kpc = kiloparsec (1000 pc) D L - luminosity distance, obtaining an objects distance using only visual aspects

  6. List of unusual units of measurement - Wikipedia

    en.wikipedia.org/wiki/List_of_unusual_units_of...

    It would be exactly 1 km if the original definition of 1 metre = 1 ⁄ 10,000 quarter-meridian had been adhered to. One disadvantage is that common angles like 30° and 60° are expressed by fractional values ( 33 + 1 ⁄ 3 and 66 + 2 ⁄ 3 respectively) so this "decimal" unit failed to displace the "sexagesimal" units equilateral-vertex ...

  7. 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 ...

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    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 length - Wikipedia

    en.wikipedia.org/wiki/Unit_of_length

    Earth radius R 🜨 ≈ 6,371 km [9] Lunar distance LD ≈ 384 402 km. [10] Average distance between the center of Earth and the center of the Moon. astronomical unit au. Defined as 149 597 870 700 m. [11] Approximately the distance between the Earth and Sun. light-year ly ≈ 9 460 730 472 580.8 km. The distance that light travels in a vacuum ...