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  2. Parsec - Wikipedia

    en.wikipedia.org/wiki/Parsec

    [a] The parsec unit is obtained by the use of parallax and trigonometry, and is defined as the distance at which 1 AU subtends an angle of one arcsecond [1] (⁠ 1 / 3600 ⁠ of a degree). The nearest star, Proxima Centauri , is about 1.3 parsecs (4.2 light-years) from the Sun : from that distance, the gap between the Earth and the Sun spans ...

  3. 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).

  4. Stellar parallax - Wikipedia

    en.wikipedia.org/wiki/Stellar_parallax

    Stellar parallax is the basis for the parsec, which is the distance from the Sun to an astronomical object that has a parallax angle of one arcsecond. (1 AU and 1 parsec are not to scale, 1 parsec = ~206265 AU) Stellar parallax is the apparent shift of position of any

  5. Parallax - Wikipedia

    en.wikipedia.org/wiki/Parallax

    Parallax is an angle subtended by two lines crossing a point. In the upper diagram, the Earth (blue-filled circle) in its orbit sweeps the parallax angle subtended on the Sun (yellow-filled circle). The lower diagram shows the equal angle swept by the Sun in a geostatic model. A similar diagram can be drawn for a star except that the angle of ...

  6. Astronomical unit - Wikipedia

    en.wikipedia.org/wiki/Astronomical_unit

    The parsec (parallax arcsecond) is defined in terms of the astronomical unit, being the distance of an object with a parallax of 1″. The light-year is often used in popular works, but is not an approved non-SI unit and is rarely used by professional astronomers.

  7. Cosmic distance ladder - Wikipedia

    en.wikipedia.org/wiki/Cosmic_distance_ladder

    Parallax is an angle subtended by two lines crossing a point. ... measuring 1 arcsecond for an object at 1 parsec's ... Finding the value of the Hubble constant was ...

  8. Minute and second of arc - Wikipedia

    en.wikipedia.org/wiki/Minute_and_second_of_arc

    The unit of distance called the parsec, abbreviated from the parallax angle of one arc second, was developed for such parallax measurements. The distance from the Sun to a celestial object is the reciprocal of the angle, measured in arcseconds, of the object's apparent movement caused by parallax.

  9. Absolute magnitude - Wikipedia

    en.wikipedia.org/wiki/Absolute_magnitude

    Because Solar System bodies are illuminated by the Sun, their brightness varies as a function of illumination conditions, described by the phase angle. This relationship is referred to as the phase curve. The absolute magnitude is the brightness at phase angle zero, an arrangement known as opposition, from a distance of one AU.