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  2. Light-year - Wikipedia

    en.wikipedia.org/wiki/Light-year

    The product of Simon Newcomb's J1900.0 mean tropical year of 31 556 925.9747 ephemeris seconds and a speed of light of 299 792.5 km/s produced a light-year of 9.460 530 × 10 15 m (rounded to the seven significant digits in the speed of light) found in several modern sources [10] [11] [12] was probably derived from an old source such as C. W ...

  3. Cosmic distance ladder - Wikipedia

    en.wikipedia.org/wiki/Cosmic_distance_ladder

    The amount of shift is quite small, even for the nearest stars, measuring 1 arcsecond for an object at 1 parsec's distance (3.26 light-years), and thereafter decreasing in angular amount as the distance increases. Astronomers usually express distances in units of parsecs (parallax arcseconds); light-years are used in popular media.

  4. Minute and second of arc - Wikipedia

    en.wikipedia.org/wiki/Minute_and_second_of_arc

    an object of diameter 45 866 916 km at one light-year, an object of diameter one astronomical unit (149 597 870.7 km) at a distance of one parsec, per the definition of the latter. [7] One milliarcsecond is about the size of a half dollar, seen from a distance equal to that between the Washington Monument and the Eiffel Tower.

  5. Orders of magnitude (length) - Wikipedia

    en.wikipedia.org/wiki/Orders_of_magnitude_(length)

    3.1 Em – 310 light-years – distance to Canopus according to Hipparcos [202] 3.9 Em – 410 light-years – distance to Betelgeuse according to Hipparcos [203] 6.2 Em – 650 light-years – distance to the Helix Nebula, located in the constellation Aquarius [204] 8.2 Em – 860 light-years – distance to Rigel according to Hipparcos [202]

  6. Stellar parallax - Wikipedia

    en.wikipedia.org/wiki/Stellar_parallax

    The parsec (3.26 light-years) is defined as the distance for which the annual parallax is 1 arcsecond. Annual parallax is normally measured by observing the position of a star at different times of the year as Earth moves through its orbit. The angles involved in these calculations are very small and thus difficult to measure.

  7. Proper motion - Wikipedia

    en.wikipedia.org/wiki/Proper_motion

    The first is the direction of the proper motion on the celestial sphere (with 0 degrees meaning the motion is north, 90 degrees meaning the motion is east, (left on most sky maps and space telescope images) and so on), and the second is its magnitude, typically expressed in arcseconds per year (symbols: arcsec/yr, as/yr, ″/yr, ″ yr −1) or ...

  8. Parsec - Wikipedia

    en.wikipedia.org/wiki/Parsec

    The use of the parsec as a unit of distance follows naturally from Bessel's method, because the distance in parsecs can be computed simply as the reciprocal of the parallax angle in arcseconds (i.e.: if the parallax angle is 1 arcsecond, the object is 1 pc from the Sun; if the parallax angle is 0.5 arcseconds, the object is 2 pc away; etc.).

  9. Parallax in astronomy - Wikipedia

    en.wikipedia.org/wiki/Parallax_in_astronomy

    A parsec is the distance from the Sun to an astronomical object that has a parallax angle of one arcsecond (not to scale). The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System, approximately equal to 3.26 light-years or 206,265 astronomical units (AU), i.e. 30.9 trillion kilometres (19.2 trillion miles).