| 词条 | DR 21 |
| 释义 |
|name = DR 21 |image = Stars in the DR21 Region (crop).jpg |image_size = 275px |caption = Infrared view of the DR 21 molecular cloud |type = Molecular cloud |subtype = Emission nebula |epoch = J2000 |ra = {{RA|20|39|01.6}} |dec = {{DEC|+42|19|38}} |dist_ly = 6,000 |dist_pc = 1,800 |constellation = Cygnus |names = {{nowrap|GRS G081.70 +00.50}}, {{nowrap|GAL 081.681+00.54}}, {{nowrap|W 75}}, {{nowrap|18P 78}}, {{nowrap|36P 19}}, {{nowrap|RAFGL 2624}} }}DR 21 is a large molecular cloud[1] located in the constellation Cygnus, discovered in 1966 as a radio continuum source by Downes and Rinehart.[2] DR 21 is located about {{convert|6000|ly|pc}} from Earth and extends for {{convert|80|ly|pc}}.[3] The region contains a high rate of star formation and is associated with the Cygnus X star forming region. It has an estimated mass of {{solar mass|1,000,000|link=y}}.[4] A number of different molecules have been detected in the region by their radio emission, including formaldehyde, ammonia, water and carbon monoxide.[5] In this region, some of the most massive stars in the Milky Way have been observed. {{nowrap|DR 21}} contains complex patterns of dust and gas, which glow in the infrared due to the presence of organic compounds known as polycyclic aromatic hydrocarbons. Jagged patterns within {{nowrap|DR 21}} result from interactions with interstellar wind, radiation pressure, magnetic fields, and gravity.[6] An estimated population of 2,900 stars have been formed in this molecular cloud, similar to the population of the Orion Nebula cluster, which are distributed in groups associated with cloud clumps.[7] Feedback from the massive stars may ultimately disrupt the cloud; however, this has not happened yet due to the region's extreme youth. Study of these stars by the Spitzer Space Telescope has shown signs of protoplanetary disks.[8] References1. ^{{cite journal |title=Observations of the line profiles of H2 in the DR 21 molecular cloud |journal=The Astronomical Journal |first1=Daniel |last1=Nadeau |first2=Stephane |last2=Beland |volume=95 |pages=136–140 |date=January 1988 |doi=10.1086/114621 |bibcode=1988AJ.....95..136N}} 2. ^{{cite journal |title=Microwave Observations of the Cygnus X Region |journal=The Astrophysical Journal |first1=D. |last1=Downes |first2=R. |last2=Rinehart |volume=144 |page=937 |date=June 1966 |doi=10.1086/148691 |bibcode=1966ApJ...144..937D}} 3. ^{{cite book |url=https://books.google.com/books?id=CqrWEBWPfYoC&pg=PA246&lpg=PA246 |title=Universe: The Definitive Visual Guide |publisher=Dorling Kindersley |location=New York |editor-first=Martin J. |editor-last=Rees |page=246 |date=October 2012 |isbn=978-0-7566-9841-6}} 4. ^{{cite journal |title=The Internal Structure of Molecular Clouds. I. C18O, C34S and NH3 Maps of the DR 21/W 75 S Region |journal=Astronomy and Astrophysics |first1=T. L. |last1=Wilson |first2=R. |last2=Mauersberger |volume=239 |issue=1-2 |pages=305–318 |date=November 1990 |bibcode=1990A&A...239..305W}} 5. ^{{cite web |url=http://www.gb.nrao.edu/~glangsto/dr21/ |title=DR21: Star Forming Region in Constellation Cygnus |publisher=National Radio Astronomy Observatory |first=Glen |last=Langston |date=2001 |accessdate=24 December 2015}} 6. ^{{cite journal |title=Interferometric Mapping of Magnetic Fields in Star-forming Regions. III. Dust and CO Polarization in DR 21(OH) |journal=The Astrophysical Journal |first1=Shih-Ping |last1=Lai |first2=José M. |last2=Girart |first3=Richard M. |last3=Crutcher |volume=598 |issue=1 |pages=392–399 |date=November 2003 |arxiv=astro-ph/0308051 |bibcode=2003ApJ...598..392L |doi=10.1086/378769}} 7. ^{{cite journal |title=The Spatial Structure of Young Stellar Clusters. II. Total Young Stellar Populations |journal=The Astrophysical Journal |first1=Michael A. |last1=Kuhn |first2=Konstantin V. |last2=Getman |first3=Eric D. |last3=Feigelson |volume=802 |issue=1 |at=60 |date=March 2015 |arxiv=1501.05300 |bibcode=2015ApJ...802...60K |doi=10.1088/0004-637X/802/1/60}} 8. ^{{cite journal |title=The MYStIX Infrared-Excess Source Catalog |journal=The Astrophysical Journal Supplement |first1=Matthew S. |last1=Povich |first2=Michael A. |last2=Kuhn |first3=Konstantin V. |last3=Getman |first4=Heather A. |last4=Busk |first5=Eric D. |last5=Feigelson |first6=Patrick S. |last6=Broos |first7=Leisa K. |last7=Townsley |first8=Robert R. |last8=King |first9=Tim |last9=Naylor |display-authors=5 |volume=209 |issue=2 |at=31 |date=December 2013 |arxiv=1309.4497 |bibcode=2013ApJS..209...31P |doi=10.1088/0067-0049/209/2/31}} External links{{commons category-inline|DR 21}}
4 : Molecular clouds|Emission nebulae|Cygnus (constellation)|Star-forming regions |
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