| 词条 | Messier 78 |
| 释义 |
| name = M78 | image = Messier 78.jpg | caption = Image of Messier 78 captured using the Wide Field Imager camera on the MPG/ESO 2.2-metre telescope at the La Silla Observatory. | type = Reflection | epoch = J2000.0 | ra = {{RA|05|46|46.7}} | dec = {{DEC|+00|00|50}} | dist_ly = {{Convert|415|pc|ly|order=flip|abbr=on|lk=on}}[3] | appmag_v = 8.3 | size_v = 8′ × 6′ | constellation = Orion | radius_ly = 5 | absmag_v = | notes = Part of the Orion Complex | names = Ced 55u, DG 80, IRAS 05442-0000, [KPS2012] MWSC 0664, NGC 2068 }}Messier 78 or M 78, also known as NGC 2068, is a reflection nebula in the constellation Orion. It was discovered by Pierre Méchain in 1780 and included by Charles Messier in his catalog of comet-like objects that same year.[5] M78 is the brightest diffuse reflection nebula of a group of nebulae that includes NGC 2064, NGC 2067 and NGC 2071. This group belongs to the Orion B molecular cloud complex and is about {{Convert|415|pc|ly|order=flip|disp=out|lk=on}} distant from Earth.[3] M78 is easily found in small telescopes as a hazy patch and involves two stars of 10th and 11th magnitude. These two B-type stars, {{nowrap|HD 38563 A}} and {{nowrap|HD 38563 B}}, are responsible for making the cloud of dust in M78 visible by reflecting their light.[7] The M78 cloud contains a cluster of stars that is visible in the infrared.[3] Due to gravity, the molecular gas in the nebula has fragmented into a hierarchy of clumps,[3] the denser cores of which about to form stars with masses of up to {{Val|5|ul=solar mass}}.[10] About 45 variable stars of the T Tauri type,[11] young stars still in the process of formation as well as some 17[12] Herbig–Haro objects are known in M78. GallerySee also
References1. ^1 {{citation | first1=Hartmut | last1=Frommert | first2=Christine | last2=Kronberg | title=Messier 78 | work=SEDS Messier pages | publisher=Students for the Exploration and Development of Space (SEDS) | date=October 9, 2018 | url=http://messier.seds.org/m/m078.html | accessdate=2018-12-05 | postscript=. }} [1][2][3][4][5][6]2. ^1 {{citation | title=Emission-Line Stars in the Region of NGC 2068 | last1=Herbig | first1=G. H. | last2=Kuhi | first2=L. V. | journal=Astrophysical Journal | postscript=. | volume=137 | pages=398 | date=February 1963 | doi=10.1086/147519 | bibcode=1963ApJ...137..398H }} 3. ^1 {{citation | title=Newly Discovered Herbig-Haro Objects in the NGC 2068 and NGC 2071 Regions | last1=Zhao | first1=Bing | last2=Wang | first2=Min | last3=Yang | first3=Ji | last4=Wang | first4=Hongchi | last5=Deng | first5=Licai | last6=Yan | first6=Jun | last7=Chen | first7=Jiansheng | display-authors=1 | journal=The Astronomical Journal | postscript=. | volume=118 | issue=3 | pages=1347–1353 | date=September 1999 | doi=10.1086/301002 | bibcode=1999AJ....118.1347Z }} 4. ^1 {{citation | title=Infrared and optical observations of Herbig-Haro objects. | last1=Strom | first1=S. E. | last2=Grasdalen | first2=G. L. | last3=Strom | first3=K. M. | display-authors=1 | journal=Astrophysical Journal | postscript=. | volume=191 | pages=111–142 | date=July 1974 | doi=10.1086/152948 | bibcode=1974ApJ...191..111S }} 5. ^1 {{citation | title=A SCUBA survey of the NGC 2068/2071 protoclusters | last1=Motte | first1=F. | last2=André | first2=P. | last3=Ward-Thompson | first3=D. | last4=Bontemps | first4=S. | journal=Astronomy and Astrophysics | display-authors=1 | volume=372 | issue=3 | pages=L41–L44 | date=June 2001 | doi=10.1051/0004-6361:20010543 | postscript=. | bibcode=2001A&A...372L..41M | arxiv=astro-ph/0105019 }} 6. ^1 2 3 4 {{citation | title=The structure and kinematics of dense gas in NGC 2068 | last1=Walker-Smith | first1=S. L. | last2=Richer | first2=J. S. | last3=Buckle | first3=J. V. | last4=Smith | first4=R. J. | last5=Greaves | first5=J. S. | last6=Bonnell | first6=I. A. | journal=Monthly Notices of the Royal Astronomical Society | volume=429 | issue=4 | pages=3252–3265 | date=March 2013 | doi=10.1093/mnras/sts582 | arxiv=1212.2018 | bibcode=2013MNRAS.429.3252W | postscript=. }} }} External links{{commons category|Messier 78}}
8 : Reflection nebulae|Orion Molecular Cloud Complex|Orion–Cygnus Arm|Orion (constellation)|Messier objects|NGC objects|Astronomical objects discovered in 1780|Discoveries by Pierre Méchain |
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