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  2. Apparent magnitude - Wikipedia

    en.wikipedia.org/wiki/Apparent_magnitude

    minimum brightness [42] +1.33: star Alpha Centauri B: seen from Earth +1.86: planet Mars: seen from Earth minimum brightness [42] +1.98: star Polaris: seen from Earth mean brightness [49] +3.03: supernova SN 1987A: seen from Earth in the Large Magellanic Cloud (160,000 light-years away) +3 to +4: Faintest stars visible in an urban neighborhood ...

  3. Cosmic distance ladder - Wikipedia

    en.wikipedia.org/wiki/Cosmic_distance_ladder

    For example, all observations seem to indicate that Type Ia supernovae that are of known distance have the same brightness, corrected by the shape of the light curve. The basis for this closeness in brightness is discussed below; however, the possibility exists that the distant Type Ia supernovae have different properties than nearby Type Ia ...

  4. Magnitude (astronomy) - Wikipedia

    en.wikipedia.org/wiki/Magnitude_(astronomy)

    Note that the brighter the star, the smaller the magnitude: Bright "first magnitude" stars are "1st-class" stars, while stars barely visible to the naked eye are "sixth magnitude" or "6th-class". The system was a simple delineation of stellar brightness into six distinct groups but made no allowance for the variations in brightness within a group.

  5. Bortle scale - Wikipedia

    en.wikipedia.org/wiki/Bortle_scale

    The Bortle dark-sky scale (usually referred to as simply the Bortle scale) is a nine-level numeric scale that measures the night sky's brightness of a particular location. It quantifies the astronomical observability of celestial objects and the interference caused by light pollution .

  6. Hertzsprung–Russell diagram - Wikipedia

    en.wikipedia.org/wiki/Hertzsprung–Russell_diagram

    Galaxy color–magnitude diagram – Chart depicting the relationship between brightness and mass of large star systems; Hayashi track – Luminosity–temperature relationship in stars; Henyey track – path taken by pre-main-sequence stars in the Hertzsprung–Russell diagram

  7. Orders of magnitude (illuminance) - Wikipedia

    en.wikipedia.org/wiki/Orders_of_magnitude...

    This section lists examples of luminances, measured in candelas per square metre and grouped by order of magnitude. Factor (cd/m 2) Multiple Value Item 10 −6:

  8. Sky brightness - Wikipedia

    en.wikipedia.org/wiki/Sky_brightness

    (The S 10 unit is defined as the surface brightness of a star whose V-magnitude is 10 and whose light is smeared over one square degree, or 27.78 mag arcsec −2.) The total sky brightness in zenith is therefore ~220 S 10 or 21.9 mag/arcsec² in the V-band. Note that the contributions from Airglow and Zodiacal light vary with the time of year ...

  9. Alpha Librae - Wikipedia

    en.wikipedia.org/wiki/Alpha_Librae

    The two brightest components of Alpha Librae form a double star moving together through space as common proper motion companions. They are separated in the sky by an angular distance of 231" (3'51"). The position angle of the companion is 314 degrees. The brighter of the two is a white star of spectral type A3, with an apparent magnitude of 2.8 ...