Editing Apparent magnitude (section)

===Absolute magnitude===
{{Main|Absolute magnitude}}
While apparent magnitude is a measure of the brightness of an object as seen by a particular observer, absolute magnitude is a measure of the ''intrinsic'' brightness of an object.  Flux decreases with distance according to an [[inverse-square law]], so the apparent magnitude of a star depends on both its absolute brightness and its distance (and any extinction). For example, a star at one distance will have the same apparent magnitude as a star four times as bright at twice that distance.  In contrast, the intrinsic brightness of an astronomical object, does not depend on the distance of the observer or any [[Extinction (astronomy)|extinction]].<ref>{{Cite web |title=Lecture 4: Page 3, Properties of the Stars |url=https://homepages.uc.edu/~hansonmm/ASTRO/LECTURENOTES/W03/Lec6/Page3.html |access-date=2024-12-05 |website=homepages.uc.edu}}</ref>

The absolute magnitude {{mvar|M}}, of a star or astronomical object is defined as the apparent magnitude it would have as seen from a distance of {{convert|10|pc|ly|lk=out}}. The absolute magnitude of the Sun is 4.83 in the V band (visual), 4.68 in the [[Gaia (spacecraft)|Gaia satellite's]] G band (green) and 5.48 in the B band (blue).<ref name="Bband">{{cite web | title=Some Useful Astronomical Definitions | publisher=Stony Brook Astronomy Program | first=Aaron | last=Evans | url=http://www.astro.sunysb.edu/aevans/PHY523/classnotes523/useful-definitions-pp.pdf | access-date=12 July 2009 | archive-url=https://web.archive.org/web/20110720052227/http://www.astro.sunysb.edu/aevans/PHY523/classnotes523/useful-definitions-pp.pdf | archive-date=20 July 2011 | url-status=live}}</ref><ref name="Gband">{{cite journal | last1=Čotar | first1=Klemen | last2=Zwitter | first2=Tomaž | last3=Traven | first3=Gregor | last4=Kos | first4=Janez | last5=Asplund | first5=Martin | last6=Bland-Hawthorn | first6=Joss | last7=Buder | first7=Sven | last8=D'Orazi | first8=Valentina | last9=De Silva | first9=Gayandhi M | last10=Lin | first10=Jane | last11=Martell | first11=Sarah L | last12=Sharma | first12=Sanjib | last13=Simpson | first13=Jeffrey D | last14=Zucker | first14=Daniel B | last15=Horner | first15=Jonathan | last16=Lewis | first16=Geraint F | last17=Nordlander | first17=Thomas | last18=Ting | first18=Yuan-Sen | last19=Wittenmyer | first19=Rob A |display-authors=2 | title=The GALAH survey: unresolved triple Sun-like stars discovered by the Gaia mission | journal=Monthly Notices of the Royal Astronomical Society | publisher=Oxford University Press (OUP) | volume=487 | issue=2 | date=21 May 2019 | issn=0035-8711 | doi=10.1093/mnras/stz1397 |arxiv=1904.04841  |doi-access=free | pages=2474–2490}}</ref><ref name="Bessell2005">{{cite journal|last1=Bessell|first1=Michael S.|title=Standard Photometric Systems|journal=Annual Review of Astronomy and Astrophysics|volume=43|issue=1|date=September 2005|pages=293–336|issn=0066-4146|doi=10.1146/annurev.astro.41.082801.100251|bibcode=2005ARA&A..43..293B|url=http://www.mso.anu.edu.au/~bessell/araapaper.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.mso.anu.edu.au/~bessell/araapaper.pdf |archive-date=9 October 2022 |url-status=live}}</ref>

In the case of a planet or asteroid, the absolute magnitude {{mvar|H}} rather means the apparent magnitude it would have if it were {{convert|1|AU|km|lk=in}} from both the observer and the Sun, and fully illuminated at maximum opposition (a configuration that is only theoretically achievable, with the observer situated on the surface of the Sun).<ref name="Luciuk">{{Cite web | url = http://www.asterism.org/tutorials/tut35%20Magnitudes.pdf | author = Luciuk, M. | title = Astronomical Magnitudes | page = 8 | access-date = 11 January 2019}}</ref>