Apparent magnitude - wikipedia Apparent magnitude For a more detailed discussion of the history of the magnitude system, see Magnitude ( astronomy ). Asteroid 65 Cybele and two stars, with their magnitudes labeled The apparent magnitude ( m ) of a celestial object is a number that is a measure of its brightness as seen by an observer on Earth. The brighter an object appears, the lower its magnitude value ( i.e. inverse relation ). The Sun, at apparent magnitude of − 27, is the brightest object in the sky. It is adjusted to the value it would have in the absence of the atmosphere. Furthermore, the magnitude scale is logarithmic ; a difference of one in magnitude corresponds to a change in brightness by a factor of √ 100, or about 2.512. The measurement of apparent magnitudes or brightnesses of celestial objects is known as photometry. Apparent magnitudes are used to quantify the brightness of sources at ultraviolet, visible, and infrared wavelengths. An apparent magnitude is usually measured in a specific passband corresponding to some photometric system such as the UBV system. In standard astronomical notation, an apparent magnitude in the V ( `` visual '' ) filter band would be denoted either as m or often simply as V, as in `` m = 15 '' or `` V = 15 '' to describe a 15th - magnitude object. Contents 1 History 2 Calculations 2.1 Example : Sun and Moon 2.2 Magnitude addition 2.3 Absolute magnitude 3 Standard reference values 4 Table of notable celestial objects 5 See also 6 References 7 External links History Visible to typical human eye Apparent magnitude Bright - ness relative to Vega Number of stars brighter than apparent magnitude in the night sky Yes − 1.0 250 % 1 ( Sirius ) 00.0 100 % 01.0 40 % 15 02.0 16 % 48 03.0 6.3 % 171 04.0 2.5 % 513 05.0 1.0 % 7003160200000000000 ♠ 1602 06.0 0.4 % 7003480000000000000 ♠ 4800 06.5 0.25 % 7003909600000000000 ♠ 9096 No 07.0 0.16 % 7004140000000000000 ♠ 14 000 08.0 0.063 % 7004420000000000000 ♠ 42 000 09.0 0.025 % 7005121000000000000 ♠ 121 000 10.0 0.010 % 7005340000000000000 ♠ 340 000 The scale used to indicate magnitude originates in the Hellenistic practice of dividing stars visible to the naked eye into six magnitudes. The brightest stars in the night sky were said to be of first magnitude ( m = 1 ), whereas the faintest were of sixth magnitude ( m = 6 ), which is the limit of human visual perception ( without the aid of a telescope ). Each grade of magnitude was considered twice the brightness of the following grade ( a logarithmic scale ), although that ratio was subjective as no photodetectors existed. This rather crude scale for the brightness of stars was popularized by Ptolemy in his Almagest, and is generally believed to have originated with Hipparchus. In 1856, Norman Robert Pogson formalized the system by defining a first magnitude star as a star that is 100 times as bright as a sixth - magnitude star, thereby establishing the logarithmic scale still in use today. This implies that a star of magnitude m is 2.512 times as bright as a star of magnitude m + 1. This figure, the fifth root of 100, became known as Pogson 's Ratio. The zero point of Pogson 's scale was originally defined by assigning Polaris a magnitude of exactly 2. Astronomers later discovered that Polaris is slightly variable, so they switched to Vega as the standard reference star, assigning the brightness of Vega as the definition of zero magnitude at any specified wavelength. Apart from small corrections, the brightness of Vega still serves as the definition of zero magnitude for visible and near infrared wavelengths, where its spectral energy distribution ( SED ) closely approximates that of a black body for a temperature of 7004110000000000000 ♠ 11 000 K. However, with the advent of infrared astronomy it was revealed that Vega 's radiation includes an Infrared excess presumably due to a circumstellar disk consisting of dust at warm temperatures ( but much cooler than the star 's surface ). At shorter ( e.g. visible ) wavelengths, there is negligible emission from dust at these temperatures. However, in order to properly extend the magnitude scale further into the infrared, this peculiarity of Vega should not affect the definition of the magnitude scale. Therefore, the magnitude scale was extrapolated to all wavelengths on the basis of the black body radiation curve for an ideal stellar surface at 7004110000000000000 ♠ 11 000 K uncontaminated by circumstellar radiation. On this basis the spectral irradiance ( usually expressed in janskys ) for the zero magnitude point, as a function of wavelength can be computed. Small deviations are specified between systems using measurement apparatuses developed independently so that data obtained by different astronomers can be properly compared ; of greater practical importance is the definition of magnitude not at a single wavelength but applying to the response of standard spectral filters used in photometry over various wavelength bands. With the modern magnitude systems, brightness over a very wide range is specified according to the logarithmic definition detailed below, using this zero reference. In practice such apparent magnitudes do not exceed 30 ( for detectable measurements ). The brightness of Vega is exceeded by four stars in the night sky at visible wavelengths ( and more at infrared wavelengths ) as well as bright planets such as Venus, Mars, and Jupiter, and these must be described by negative magnitudes. For example, Sirius, the brightest star of the celestial sphere, has an apparent magnitude of − 1.4 in the visible ; negative magnitudes for other very bright astronomical objects can be found in the table below. Astronomers have developed other photometric zeropoint systems as alternatives to the Vega system. The most widely used is the AB magnitude system, in which photometric zeropoints are based on a hypothetical reference spectrum having constant flux per unit frequency interval, rather than using a stellar spectrum or blackbody curve as the reference. The AB magnitude zeropoint is defined such that an object 's AB and Vega - based magnitudes will be approximately equal in the V filter band. Calculations 30 Doradus image taken by ESO 's VISTA. This nebula has an apparent magnitude of 8. A graph of apparent magnitude against brightness As the amount of light actually received by a telescope is reduced by transmission through the Earth 's atmosphere, any measurement of apparent magnitude is corrected for what it would have been as seen from above the atmosphere. The dimmer an object appears, the higher the numerical value given to its apparent magnitude, with a difference of 5 magnitudes corresponding to a brightness factor of exactly 100. Therefore, the apparent magnitude m, in the spectral band x, would be given by m x = − 5 log 100 ⁡ ( F x F x, 0 ), ( displaystyle m_ ( x ) = - 5 log _ ( 100 ) left ( ( \frac ( F_ ( x ) ) ( F_ ( x, 0 ) ) ) \right ), ) which is more commonly expressed in terms of common ( base - 10 ) logarithms as m x = − 2.5 log 10 ⁡ ( F x F x, 0 ), ( displaystyle m_ ( x ) = - 2.5 log _ ( 10 ) left ( ( \frac ( F_ ( x ) ) ( F_ ( x, 0 ) ) ) \right ), ) where F is the observed flux density using spectral filter x, and F is the reference flux ( zero - point ) for that photometric filter. Since an increase of 5 magnitudes corresponds to a decrease in brightness by a factor of exactly 100, each magnitude increase implies a decrease in brightness by the factor √ 100 ≈ 2.512 ( Pogson 's ratio ). Inverting the above formula, a magnitude difference m − m = Δm implies a brightness factor of F 2 F 1 = 100 Δ m 5 = 10 0.4 Δ m ≈ 2.512 Δ m. ( displaystyle ( \frac ( F_ ( 2 ) ) ( F_ ( 1 ) ) ) = 100 ^ ( \frac ( Delta m ) ( 5 ) ) = 10 ^ ( 0.4 Delta m ) approx 2.512 ^ ( Delta m ). ) Example : Sun and moon What is the ratio in brightness between the Sun and the full Moon ? The apparent magnitude of the Sun is − 26.74 ( brighter ), and the mean apparent magnitude of the full moon is − 12.74 ( dimmer ). Difference in magnitude : x = m 1 − m 2 = ( − 12.74 ) − ( − 26.74 ) = 14.00. ( displaystyle x = m_ ( 1 ) - m_ ( 2 ) = ( - 12.74 ) - ( - 26.74 ) = 14.00. ) Brightness factor : v b = 10 0.4 x = 10 0.4 × 14.00 ≈ 398 107.17. ( displaystyle v_ ( b ) = 10 ^ ( 0.4 x ) = 10 ^ ( 0.4 \times 14.00 ) approx 398 , 107.17. ) The Sun appears about 7005400000000000000 ♠ 400 000 times brighter than the full moon. Magnitude addition Sometimes one might wish to add brightnesses. For example, photometry on closely separated double stars may only be able to produce a measurement of their combined light output. How would we reckon the combined magnitude of that double star knowing only the magnitudes of the individual components ? This can be done by adding the brightnesses ( in linear units ) corresponding to each magnitude. 10 − m f × 0.4 = 10 − m 1 × 0.4 + 10 − m 2 × 0.4. ( displaystyle 10 ^ ( - m_ ( f ) \times 0.4 ) = 10 ^ ( - m_ ( 1 ) \times 0.4 ) + 10 ^ ( - m_ ( 2 ) \times 0.4 ). ) Solving for m f ( displaystyle m_ ( f ) ) yields m f = − 2.5 log 10 ⁡ ( 10 − m 1 × 0.4 + 10 − m 2 × 0.4 ), ( displaystyle m_ ( f ) = - 2.5 log _ ( 10 ) left ( 10 ^ ( - m_ ( 1 ) \times 0.4 ) + 10 ^ ( - m_ ( 2 ) \times 0.4 ) \right ), ) where m is the resulting magnitude after adding the brightnesses referred to by m and m. Absolute magnitude Main article : Absolute magnitude Since flux decreases with distance according to the inverse - square law, a particular apparent magnitude could equally well refer to a star at one distance, or a star four times brighter at twice that distance, and so on. When one is not interested in the brightness as viewed from Earth, but the intrinsic brightness of an astronomical object, then one refers not to the apparent magnitude but the absolute magnitude. The absolute magnitude M, of a star or astronomical object is defined as the apparent magnitude it would have as seen from a distance of 10 parsecs ( about 32.6 light - years ). The absolute magnitude of the Sun is 4.83 in the V band ( yellow ) and 5.48 in the B band ( blue ). In the case of a planet or asteroid, the absolute magnitude H rather means the apparent magnitude it would have if it were 1 astronomical unit from both the observer and the Sun, and fully illuminated ( a configuration that is only theoretically achievable, with the observer situated on the surface of the Sun ). Standard reference values Standard apparent magnitudes and fluxes for typical bands Band λ ( μm ) Δλ / λ ( FWHM ) Flux at m = 0, F Jy 10 erg / ( s cm Hz ) U 0.36 0.15 1810 1.81 0.44 0.22 4260 4.26 V 0.55 0.16 3640 3.64 0.64 0.23 3080 3.08 0.79 0.19 2550 2.55 1.26 0.16 1600 1.60 1.60 0.23 1080 1.08 2.22 0.23 0670 0.67 3.50 g 0.52 0.14 3730 3.73 r 0.67 0.14 4490 4.49 i 0.79 0.16 4760 4.76 z 0.91 0.13 4810 4.81 It is important to note that the scale is logarithmic : the relative brightness of two objects is determined by the difference of their magnitudes. For example, a difference of 3.2 means that one object is about 19 times as bright as the other, because Pogson 's Ratio raised to the power 3.2 is approximately 19.05. A common misconception is that the logarithmic nature of the scale is because the human eye itself has a logarithmic response. In Pogson 's time this was thought to be true ( see Weber -- Fechner law ), but it is now believed that the response is a power law ( see Stevens ' power law ). Magnitude is complicated by the fact that light is not monochromatic. The sensitivity of a light detector varies according to the wavelength of the light, and the way it varies depends on the type of light detector. For this reason, it is necessary to specify how the magnitude is measured for the value to be meaningful. For this purpose the UBV system is widely used, in which the magnitude is measured in three different wavelength bands : U ( centred at about 350 nm, in the near ultraviolet ), B ( about 435 nm, in the blue region ) and V ( about 555 nm, in the middle of the human visual range in daylight ). The V band was chosen for spectral purposes and gives magnitudes closely corresponding to those seen by the light - adapted human eye, and when an apparent magnitude is given without any further qualification, it is usually the V magnitude that is meant, more or less the same as visual magnitude. Because cooler stars, such as red giants and red dwarfs, emit little energy in the blue and UV regions of the spectrum their power is often under - represented by the UBV scale. Indeed, some L and T class stars have an estimated magnitude of well over 100, because they emit extremely little visible light, but are strongest in infrared. Measures of magnitude need cautious treatment and it is extremely important to measure like with like. On early 20th century and older orthochromatic ( blue - sensitive ) photographic film, the relative brightnesses of the blue supergiant Rigel and the red supergiant Betelgeuse irregular variable star ( at maximum ) are reversed compared to what human eyes perceive, because this archaic film is more sensitive to blue light than it is to red light. Magnitudes obtained from this method are known as photographic magnitudes, and are now considered obsolete. For objects within the Milky Way with a given absolute magnitude, 5 is added to the apparent magnitude for every tenfold increase in the distance to the object. For objects at very great distances ( far beyond the Milky Way ), this relationship must be adjusted for redshifts and for non-Euclidean distance measures due to general relativity. For planets and other Solar System bodies the apparent magnitude is derived from its phase curve and the distances to the Sun and observer. Table of notable celestial objects Apparent visual magnitudes of known celestial objects App. mag. ( V ) Celestial object...... as seen from − 38.00 star Rigel as seen from 1 AU. It would be seen as a large very bright bluish disk of 35 ° apparent diameter. − 30.30 star Sirius as seen from 1 AU. − 29.30 star Sun as seen from Mercury at perihelion − 27.40 star Sun as seen from Venus at perihelion − 26.74 star Sun as seen from Earth ( about 400,000 times brighter than mean full moon ) − 25.60 star Sun as seen from Mars at aphelion − 25.00 Minimum brightness that causes the typical eye slight pain to look at − 23.00 star Sun as seen from Jupiter at aphelion − 21.70 star Sun as seen from Saturn at aphelion − 20.20 star Sun as seen from Uranus at aphelion − 19.30 star Sun as seen from Neptune − 18.20 star Sun as seen from Pluto at aphelion − 16.70 star Sun as seen from Eris at aphelion − 14.20 An illumination level of 1 lux − 12.90 full moon maximum brightness of perigee + perihelion full moon ( mean distance value is − 12.74, though both values are about 0.18 magnitude brighter when including the opposition effect ) − 11.20 star Sun as seen from Sedna at aphelion − 10.00 Comet Ikeya -- Seki ( 1965 ) which was the brightest Kreutz Sungrazer of modern times 0 − 9.50 Iridium ( satellite ) flare maximum brightness 0 − 7.50 supernova of 1006 the brightest stellar event in recorded history ( 7200 light - years away ) 0 − 6.50 The total integrated magnitude of the night sky as seen from Earth 0 − 6.00 Crab Supernova of 1054 ( 6500 light - years away ) 0 − 5.90 International Space Station when the ISS is at its perigee and fully lit by the Sun 0 − 4.89 planet Venus maximum brightness when illuminated as a crescent 0 − 4 Faintest objects observable during the day with naked eye when Sun is high 0 − 3.99 star Epsilon Canis Majoris maximum brightness of 4.7 million years ago, the historical brightest star of the last and next five million years 0 − 3.82 planet Venus minimum brightness when it is on the far side of the Sun 0 − 2.94 planet Jupiter maximum brightness 0 − 2.91 planet Mars maximum brightness 0 − 2.5 Faintest objects visible during the day with naked eye when Sun is less than 10 ° above the horizon 0 − 2.50 new moon minimum brightness 0 − 2.45 planet Mercury maximum brightness at superior conjunction ( unlike Venus, Mercury is at its brightest when on the far side of the Sun, the reason being their different phase curves ) 0 − 1.61 planet Jupiter minimum brightness 0 − 1.47 star Sirius Brightest star ( except for the Sun ) at visible wavelengths 0 − 0.83 star Eta Carinae apparent brightness as a supernova impostor in April 1843 0 − 0.72 star Canopus 2nd brightest star 0 − 0.49 planet Saturn maximum brightness at opposition and perihelion when the rings are full open ( 2003 ) 0 − 0.27 star system Alpha Centauri AB The total magnitude ( 3rd brightest star to the naked eye ) 0 − 0.04 star Arcturus 4th brightest star to the naked eye 0 − 0.01 star Alpha Centauri A 4th brightest individual star visible telescopically in the sky 0 + 0.03 star Vega which was originally chosen as a definition of the zero point 0 + 0.50 star Sun as seen from Alpha Centauri 0 + 1.47 planet Saturn minimum brightness 0 + 1.84 planet Mars minimum brightness 0 + 3.03 supernova SN 1987A in the Large Magellanic Cloud ( 160,000 light - years away ) 0 3... 4 Faintest stars visible in an urban neighborhood with naked eye 00 3.44 Andromeda Galaxy M31 00 4.38 moon Ganymede maximum brightness ( moon of Jupiter and the largest moon in the Solar System ) 00 4.50 open cluster M41 an open cluster that may have been seen by Aristotle 00 5.20 asteroid Vesta maximum brightness 00 5.32 planet Uranus maximum brightness 00 5.72 spiral galaxy M33 which is used as a test for naked eye seeing under dark skies 00 5.73 planet Mercury minimum brightness 00 5.8 gamma - ray burst GRB 080319B Peak visual magnitude ( the `` Clarke Event '' ) seen on Earth on March 19, 2008 from a distance of 7.5 billion light - years. 00 5.95 planet Uranus minimum brightness 00 6.49 asteroid Pallas maximum brightness 00 6.5 Approximate limit of stars observed by a mean naked eye observer under very good conditions. There are about 9,500 stars visible to mag 6.5. 00 6.64 dwarf planet Ceres maximum brightness 00 6.75 asteroid Iris maximum brightness 00 6.90 spiral galaxy M81 This is an extreme naked - eyetarget that pushes human eyesight and the Bortle scale to the limit 0 7... 8 Extreme naked - eye limit, Class 1 on Bortle scale, the darkest skies available on Earth 00 7.78 planet Neptune maximum brightness 00 8.02 planet Neptune minimum brightness 00 8.10 moon Titan maximum brightness of largest moon of Saturn mean opposition magnitude 8.4 00 8.94 asteroid 10 Hygiea maximum brightness 00 9.50 Faintest objects visible using common 7 × 50 binoculars under typical conditions 010.20 moon Iapetus maximum brightness, brightest when west of Saturn and takes 40 days to switch sides 012.91 quasar 3C 273 brightest ( luminosity distance of 2.4 billion light years ) 013.42 moon Triton Maximum brightness 013.65 dwarf planet Pluto maximum brightness, 725 times fainter than magnitude 6.5 naked eye skies 015.4 centaur Chiron maximum brightness 015.55 moon Charon maximum brightness ( the large moon of Pluto ) 016.8 dwarf planet Makemake Current opposition brightness 017.27 dwarf planet Haumea Current opposition brightness of 018.7 dwarf planet Eris Current opposition brightness 020.7 moon Callirrhoe ( small ~ 8 km satellite of Jupiter ) 022 Faintest objects observable in visible light with a 600 mm ( 24 '' ) Ritchey - Chrétien telescope with 30 minutes of stacked images ( 6 subframes at 5 minutes each ) using a CCD detector 022.91 moon Hydra maximum brightness of Pluto 's moon 023.38 moon Nix maximum brightness of Pluto 's moon 025.0 moon Fenrir ( small ~ 4 km satellite of Saturn ) 027.6 planet Jupiter if it were located 5000 AU from the Sun still visiting from our earth 027.7 Faintest objects observable with an 8 - meter class ground - based telescope such as the Subaru Telescope in a 10 - hour image 028.2 Halley 's Comet in 2003 when it was 28 AU from the Sun 031.5 Faintest objects observable in visible light with Hubble Space Telescope 034 Faintest objects observable in visible light with James Webb Space Telescope 035 star LBV 1806 - 20 a luminous blue variable star, expected magnitude at visible wavelengths due to interstellar extinction See also : List of brightest stars Some of the above magnitudes are only approximate. Telescope sensitivity also depends on observing time, optical bandpass, and interfering light from scattering and airglow. See also Absolute magnitude Magnitude ( astronomy ) Photographic magnitude Luminosity in astronomy List of brightest stars List of nearest bright stars List of nearest stars Lux Surface brightness Distance modulus References ^ Jump up to : `` Vmag < 6.5 ''. SIMBAD Astronomical Database. Retrieved 2010 - 06 - 25. Jump up ^ `` Magnitude ''. National Solar Observatory -- Sacramento Peak. Archived from the original on 2008 - 02 - 06. Retrieved 2006 - 08 - 23. Jump up ^ Bright Star Catalogue Jump up ^ Pogson, N. ( 1856 ). `` Magnitudes of Thirty - six of the Minor Planets for the first day of each month of the year 1857 ''. MNRAS. 17 : 12. Bibcode : 1856MNRAS... 17... 12P. doi : 10.1093 / mnras / 17.1. 12. Jump up ^ See ( 1 ). Jump up ^ Oke, J.B. ; Gunn, J.E. ( March 15, 1983 ). `` Secondary standard stars for absolute spectrophotometry ''. 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Jump up ^ `` AstDys ( 136472 ) Makemake Ephemerides ''. Department of Mathematics, University of Pisa, Italy. Retrieved 2010 - 06 - 26. Jump up ^ `` AstDys ( 136108 ) Haumea Ephemerides ''. Department of Mathematics, University of Pisa, Italy. Retrieved 2010 - 06 - 26. Jump up ^ Steve Cullen ( sgcullen ) ( 2009 - 10 - 05 ). `` 17 New Asteroids Found by LightBuckets ''. LightBuckets. Archived from the original on 2010 - 01 - 31. Retrieved 2009 - 11 - 15. Jump up ^ Sheppard, Scott S. `` Saturn 's Known Satellites ''. Carnegie Institution ( Department of Terrestrial Magnetism ). Retrieved 2010 - 06 - 28. Jump up ^ Magnitude difference is 2.512 log ( ( 5000 / 5 ) × ( 4999 / 4 ) )  ̃ 30.6, so Jupiter is 30.6 magnitudes fainter at 5000 AU Jump up ^ What is the faintest object imaged by ground - based telescopes ?, by : The Editors of Sky Telescope, July 24, 2006 Jump up ^ `` New Image of Comet Halley in the Cold ''. ESO. 2003 - 09 - 01. Archived from the original on 1 March 2009. Retrieved 2009 - 02 - 22. Jump up ^ Illingworth, G.D. ; Magee, D. ; Oesch, P.A. ; Bouwens, R.J. ; Labbé, I. ; Stiavelli, M. ; van Dokkum, P.G. ; Franx, M. ; Trenti, M. ; Carollo, C.M. ; Gonzalez, V. ( 21 October 2013 ). `` The HST eXtreme Deep Field XDF : Combining all ACS and WFC3 / IR Data on the HUDF Region into the Deepest Field Ever ''. The Astrophysical Journal Supplement Series. 209 ( 1 ) : 6. arXiv : 1305.1931. Bibcode : 2013ApJS... 209... 6I. doi : 10.1088 / 0067 - 0049 / 209 / 1 / 6. Jump up ^ http://www.jaymaron.com/telescopes/telescopes.html ( retrieved Sep 14 2017 ) External links `` The astronomical magnitude scale ''. International Comet Quarterly. Star Formation Accretion Molecular cloud Bok globule Young stellar object Protostar Pre-main - sequence star Herbig Ae / Be Orion T Tauri FU Orionis Herbig -- Haro object Hayashi track Henyey track Evolution Main sequence Red giant branch Horizontal branch Red clump Asymptotic giant branch Protoplanetary nebula Planetary nebula PG1159 star Dredge - up Instability strip Luminous blue variable Blue straggler Stellar population Supernova Supernova impostor Hypernova Hertzsprung -- Russell diagram Color -- color diagram Luminosity class Subdwarf Dwarf Blue Red White Yellow Brown Subgiant Giant Blue Red Bright giant Supergiant Blue Red Yellow Hypergiant Yellow Spectral classification WR Be OB Subdwarf O Subdwarf B Late - type Chemically peculiar Am Ap / Bp Barium Carbon CH CN Extreme helium Lambda Boötis Lead HgMn Technetium Shell Remnants White dwarf Helium planet Neutron star Radio - quiet Pulsar Binary X-ray Magnetar Stellar black hole X-ray binary Burster Theoretical stars Black dwarf Exotic Quark Strange Preon Planck Electroweak star Dark - matter star Dark - energy star Black star Gravastar Frozen star Q star Quasi-star Thorne -- Żytkow object Iron star Blitzar Nucleosynthesis Deuterium burning Lithium burning Proton -- proton chain CNO cycle Helium flash Triple - alpha process Alpha process Carbon burning Neon burning Oxygen burning Silicon burning S - process R - process Fusor Nova Symbiotic Remnant Luminous red nova Structure Core Convection zone Microturbulence Oscillations Radiation zone Atmosphere Photosphere Starspot Chromosphere Corona Stellar wind Bubble Bipolar outflow Accretion disk Asteroseismology Helioseismology Eddington luminosity Kelvin -- Helmholtz mechanism Properties Designation Dynamics Effective temperature Kinematics Magnetic field Absolute magnitude Mass Metallicity Rotation UBV color Variable star Mira variable Star systems Binary Contact Common envelope Eclipsing Multiple Star cluster Open cluster Globular cluster Super star cluster Planetary system Earth 's Solar System Earth - centric observation of Pole star Circumpolar star Constellation Asterism Magnitude Apparent Extinction Photographic Radial velocity Proper motion Parallax Photometric - standard star Lists Star names Arabic Chinese Extremes Most massive Highest temperature Largest volume Smallest volume Brightest Historical Most luminous Nearest Nearest bright Stars with exoplanets Brown dwarfs White dwarfs Milky Way novae Notable supernovae Supernova candidates Supernova remnants Planetary nebulae Timeline of stellar astronomy Related articles Substellar object Brown dwarf Sub-brown dwarf Planet Galactic year Galaxy Supercluster Guest star Gravity Intergalactic star Infrared dark cloud Starfield Category : Stars Star portal Retrieved from `` https://en.wikipedia.org/w/index.php?title=Apparent_magnitude&oldid=813254165 '' Categories : Observational astronomy Logarithmic scales of measurement Hidden categories : Webarchive template wayback links Talk Contents About Wikipedia Alemannisch Asturianu Azərbaycanca বাংলা Беларуская Български Bosanski Català Čeština Deutsch Eesti Ελληνικά Español Esperanto Euskara فارسی Français Galego 한국어 हिन्दी Hrvatski Bahasa Indonesia Interlingua Italiano עברית ქართული Kiswahili Kreyòl ayisyen Kurdî Latina Latviešu Lëtzebuergesch Lietuvių Magyar Македонски മലയാളം मराठी Bahasa Melayu Nederlands Norsk Norsk nynorsk Occitan Oromoo Oʻzbekcha / ўзбекча ਪੰਜਾਬੀ Polski Português Română Русский Scots Sicilianu Simple English Slovenčina Slovenščina Српски / srpski Srpskohrvatski / српскохрватски Suomi Svenska Tagalog தமிழ் Татарча / tatarça ไทย Türkçe Українська Tiếng Việt West - Vlams Winaray 粵語 中文 Edit links This page was last edited on 2 December 2017, at 18 : 44. 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Question: the apparent visual magnitude of a star is a measure of the star's
Answer: brightness as seen by an observer on Earth