Editing Reflection nebula (section)

==Discovery==
[[File:Young star lights up reflection nebula IC 2631.jpg|left|thumb|Reflection nebula [[IC 2631]].<ref>{{cite web|title=A Star's Moment in the Spotlight|url=http://www.eso.org/public/news/eso1605/|access-date=10 February 2016}}</ref>]]
[[File:VdB1.jpg|thumb|200 px|left|Reflection nebula vdB1]]
Analyzing the spectrum of the nebula associated with the star [[Merope (star)|Merope]] in the [[Pleiades]], [[Vesto Slipher]] concluded in 1912 that the source of its light is most likely the star itself, and that the nebula reflects light from the star (and that of the star [[Alcyone (star)|Alcyone]]).<ref>{{cite journal|bibcode=1912LowOB...2...26S|title=On the spectrum of the nebula in the Pleiades |last1=Slipher|first1=Vesto M.|volume=2|date=1922|pages=26–27|journal=Lowell Observatory Bulletin}}</ref> Calculations by [[Ejnar Hertzsprung]] in 1913 lend credence to that hypothesis.<ref>{{cite journal|bibcode=1913AN....195..449H|title=Über die Helligkeit der Plejadennebel|last1=Hertzsprung|first1=E.|volume=195|issue=23|date=1913|pages=449–452|journal=Astronomische Nachrichten|doi = 10.1002/asna.19131952302 |url=https://zenodo.org/record/1424888}}</ref> [[Edwin Hubble]] further distinguished between the emission and reflection nebulae in 1922.<ref>{{cite journal|bibcode=1922ApJ....56..400H|title=The source of luminosity in galactic nebulae|last1=Hubble|first1=E. P.|volume=56|date=1922|pages=400|journal=Astrophysical Journal|doi=10.1086/142713|doi-access=free}}</ref>

Reflection nebula are usually blue because the scattering is more efficient for blue light than red (this is the same scattering process that gives us blue skies and red sunsets).

Reflection nebulae and emission nebulae are often seen together and are sometimes both referred to as [[diffuse nebula]]e.

Some 500 reflection nebulae are known.  A blue reflection nebula can also be seen in the same area of the sky as the [[Trifid Nebula]]. The [[Red supergiant star|supergiant star]] [[Antares]], which is very red ([[Stellar classification|spectral class]] M1), is surrounded by a large, yellow reflection nebula.

Reflection nebulae may also be the site of [[star formation]].