View source for NGC 2023

{{Short description|Emission nebula in the constellation Orion}}
{{Infobox nebula
 | name       = NGC 2023
 | image      = Barnard 33.jpg
 | caption    = NGC 2023 next to the [[Horsehead nebula]]
 | epoch      = [[J2000]]
 | constellation = [[Orion (constellation)|Orion]]<ref name="ngc" />
 | ra         = {{RA|05|41|37.9}}<ref name="simbad" />
 | dec        = {{DEC|−02|15|52}}<ref name="simbad" />
 | dist_ly    = {{Convert|400|pc|ly|order=flip|abbr=on|lk=on}}<ref name=López-García2013/>
 | appmag_v   = 
 | type       = reflection
 | type2      = [[emission nebula]]
 | size_v     = 10'×10'<ref name="ngc" />
 | radius_ly  = 
 | absmag_v   = 
 | notes      = 
 | names      = [[New General Catalogue|NGC]] 2023,<ref name="ngc" /> LBN 954, IRAS 05391-0217<ref name="simbad" />
}}

'''NGC 2023''' is an [[Emission nebula|emission]] and [[reflection nebula]] in the [[celestial equator|equatorial]] [[constellation]] of [[Orion (constellation)|Orion]]. It was discovered by the [[Germany|German]]-born astronomer [[William Herschel]] on 6 January 1785. This reflection nebula is one of the largest in the sky,<ref name=scinews2019/> with a size of {{nowrap|10 × 10 arcminutes}}.<ref name="ngc" /> It is located at a distance of {{convert|400|pc|ly|order=flip|abbr=on}} from the [[Sun]], and is positioned {{Val|15|ul=arcminute|p=~}} to the northeast of the [[Horsehead Nebula]].<ref name=López-García2013/>

This star-forming nebula forms part of the Orion B [[molecular cloud]],<ref name=López-García2013/> or [[Lynds 1630]], and is located in the northern section of this complex. In terms of [[stellar density]], it is the poorest of the four clusters embedded in the cloud complex, with only 21 embedded [[infrared]] sources.<ref name=Mookerjea2009/> The reflection nebula is illuminated by the [[Herbig Ae/Be star]] [[HD 37903]], which has a [[spectral class]] of about B2&nbsp;Ve.<ref name=Mookerjea2009/> The region around the central star is radiating fluorescent [[hydrogen line|molecular hydrogen emission]] at a near-[[infrared astronomy|infrared]] range.<ref name="1998Burton" /><ref name=Rouan1997/> Infrared emission of [[polycyclic aromatic hydrocarbons]] has been detected from the nebula's [[Cosmic dust|dust]].<ref name=Peeters2017/>

==Gallery==
<gallery>
The Birth of the Hunter.jpg|NGC 2023 taken with the [[Very Large Telescope|VLT]]'s FORS.
Sunset Glow in Orion.jpg|Southern detail of NGC 2023 ([[Hubble Space Telescope|HST]] [[Advanced Camera for Surveys|ACS]])
</gallery>

==References==
{{commons category|NGC 2023}}
{{Reflist|40em|refs=

<ref name="simbad">{{cite simbad | title=NGC 2023 | accessdate=2020-08-28 }}</ref>

<ref name=Peeters2017>{{cite journal
 | title=The PAH Emission Characteristics of the Reflection Nebula NGC 2023
 | last1=Peeters | first1=Els | last2=Bauschlicher | first2=Charles W. Jr.
 | last3=Allamandola | first3=Louis J. | last4=Tielens | first4=Alexander G. G. M.
 | last5=Ricca | first5=Alessandra | last6=Wolfire | first6=Mark G.
 | display-authors=1 | journal=The Astrophysical Journal
 | volume=836 | issue=2 | id=198 | pages=40 | date=February 2017
 | doi=10.3847/1538-4357/836/2/198 | arxiv=1701.06585
 | bibcode=2017ApJ...836..198P | s2cid=119211134 | doi-access=free }}</ref>

<ref name=scinews2019>{{cite news
 | website=Sci–News | date=May 14, 2019
 | title=ESO's Very Large Telescope Snaps Beautiful Image of Reflection Nebula
 | url=http://www.sci-news.com/astronomy/reflection-nebula-ngc-2023-07186.html
 | access-date=2020-08-28 }}</ref>

<ref name=Rouan1997>{{cite journal
 | title=The power of adaptive optics: a close look at a molecular cloud in NGC 2023
 | display-authors=1 | last1=Rouan | first1=D.
 | last2=Field | first2=D. | last3=Lemaire | first3=J. -L.
 | last4=Lai | first4=O. | last5=Pineau des Forets | first5=G.
 | last6=Falgarone | first6=E. | last7=Deltorn | first7=J. -M.
 | journal=Monthly Notices of the Royal Astronomical Society
 | volume=284 | issue=2 | pages=395–400 | date=January 1997
 | doi=10.1093/mnras/284.2.395 | bibcode=1997MNRAS.284..395R | doi-access=free }}</ref>

<ref name=Mookerjea2009>{{cite journal
 | title=Young stars and protostellar cores near NGC 2023
 | last1=Mookerjea | first1=B. | last2=Sandell | first2=G.
 | last3=Jarrett | first3=T. H. | last4=McMullin | first4=J. P.
 | display-authors=1 | journal=Astronomy and Astrophysics
 | volume=507 | issue=3 | pages=1485–1502 | date=December 2009
 | doi=10.1051/0004-6361/200912550 | arxiv=0909.2614
 | bibcode=2009A&A...507.1485M | s2cid=10603379 }}</ref>

<ref name=López-García2013>{{cite journal
 | title=A comprehensive study of NGC 2023 with XMM-Newton and Spitzer
 | display-authors=1 | last1=López-García | first1=M. A.
 | last2=López-Santiago | first2=J. | last3=Albacete-Colombo | first3=J. F.
 | last4=Pérez-González | first4=P. G. | last5=de Castro | first5=E.
 | journal=Monthly Notices of the Royal Astronomical Society
 | volume=429 | issue=1 | pages=775–791 | date=February 2013
 | doi=10.1093/mnras/sts373 | doi-access=free | arxiv=1211.2935
 | bibcode=2013MNRAS.429..775L }}</ref>

<ref name="ngc">{{Cite web
 | url=http://cseligman.com/text/atlas/ngc20.htm#2023
 | first=Courtney | last=Seligman
 | website=cseligman.com | access-date=2020-08-28
 | title=NGC Objects: NGC 2000 - 2049 }}</ref>

<ref name="1998Burton">{{cite journal
 | title=Near-IR Fluorescent Molecular Hydrogen Emission from NGC 2023
 | last1=Burton | first1=Michael G. | last2=Howe | first2=J. E.
 | last3=Geballe | first3=T. R. | last4=Brand | first4=P. W. J. L.
 | display-authors=1 | bibcode=1998PASA...15..194B
 | journal=[[Publications of the Astronomical Society of Australia]]
 | volume=15 | issue=2 | pages=194–201 | year=1998
 | doi=10.1071/AS98194 | doi-access=free | hdl=1959.4/39155 | hdl-access=free }}</ref>

}}

==External links==
*{{cite web
 | website=Hubble Space Telescope
 | url=http://www.spacetelescope.org/images/potw1130a/
 | title=Sunset glow in Orion
 | publisher=[[NASA]] | date=25 July 2011}}
* [http://vizier.u-strasbg.fr/viz-bin/VizieR-S?NGC%202023 VizieR – NGC 2023]
* [http://nedwww.ipac.caltech.edu/cgi-bin/nph-objsearch?objname=NGC%202023 NED – NGC 2023]{{WikiSky}}

{{Catalogs|NGC=2023}}
{{NGC objects:2000-2499}}
{{Sky|05|41|37.9|−|02|15|52|1}}

[[Category:Reflection nebulae]]
[[Category:Orion (constellation)]]
[[Category:Orion molecular cloud complex]]
[[Category:NGC objects|2023]]
[[Category:Discoveries by William Herschel]]
[[Category:Astronomical objects discovered in 1785]]
[[Category:Emission nebulae]]