page_title: Apparent magnitude
hierarchical_section_title: Apparent magnitude
caption_attribution_description: English: The apparent magnitude of large asteroid 65 Cybele (apmag 11.6) and stars HD 217121 (apmag 8.7) and HD 216932 (apmag 9.1). The two bright stars would be near the limit of typical 50mm binoculars. Also visible towards the upper right are the galaxies PGC194570 and PGC1016451.
context_page_description: Apparent magnitude is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's light caused by interstellar dust along the line of sight to the observer.
  The magnitude scale is reverse logarithmic: the brighter an object is, the lower its magnitude. An object that is measured to be 5 magnitudes higher than another object is 100 times dimmer. Consequently, a difference of 1.0 in magnitude corresponds to a brightness ratio of ⁵√100, or about 2.512. For example, a star of magnitude 2.0 is 2.512 times brighter than a star of magnitude 3.0 and is 100 times brighter than one of magnitude 7.0. The brightest astronomical objects have negative apparent magnitudes: for example, Venus at −4.2 or Sirius at −1.46. The faintest stars visible with the naked eye on the darkest night have apparent magnitudes of about +6.5, though this varies depending on a person's eyesight and with altitude and atmospheric conditions.
context_section_description: Apparent magnitude (m) is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's light caused by interstellar dust along the line of sight to the observer.
  The magnitude scale is reverse logarithmic: the brighter an object is, the lower its magnitude. An object that is measured to be 5 magnitudes higher than another object is 100 times dimmer. Consequently, a difference of 1.0 in magnitude corresponds to a brightness ratio of ⁵√100, or about 2.512. For example, a star of magnitude 2.0 is 2.512 times brighter than a star of magnitude 3.0 and is 100 times brighter than one of magnitude 7.0. The brightest astronomical objects have negative apparent magnitudes: for example, Venus at −4.2 or Sirius at −1.46. The faintest stars visible with the naked eye on the darkest night have apparent magnitudes of about +6.5, though this varies depending on a person's eyesight and with altitude and atmospheric conditions. The apparent magnitudes of known objects range from the Sun at −26.7 to objects in deep Hubble Space Telescope images of around magnitude +30.
  The measurement of apparent magnitude is called
  photometry. Photometric measurements are made in the ultraviolet, visible, or infrared wavelength bands using standard passband filters belonging to photometric systems such as the UBV system or the Strömgren uvbyβ system.
  Absolute magnitude is a measure of the intrinsic luminosity of a celestial object rather than its apparent brightness and is expressed on the same reverse logarithmic scale. Absolute magnitude is defined as the apparent magnitude that a star or object would have if it were observed from a distance of 10 parsecs (3.1×10¹⁴ kilometres). When referring to just "magnitude", apparent magnitude rather than absolute magnitude is normally intended.
caption: Asteroid 65 Cybele and two stars, with their magnitudes labeled
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