View source for Medusa Nebula

{{Short description|Planetary nebula in constellation Gemini}}
{{About|a planetary nebula|the Medusa Galaxy Merger|NGC 4194}}
{{Use dmy dates|date=July 2019}}
{{ Planetary nebula |
| image =Abell21 Noaoann09008a.jpg
|caption=Medusa nebula, [[Mayall Telescope]]
| name = Medusa Nebula
| type = Planetary
| epoch = J2000.0
| ra = {{RA|07|29|02.69}}<ref name="SIMBAD">{{Cite web
    |url=http://simbad.u-strasbg.fr/simbad/sim-id?protocol=html&Ident=Medusa+Nebula
    | title = MEDUSA – Planetary Nebula
    | publisher =[[Centre de Données astronomiques de Strasbourg]]
    | access-date = 1 July 2010 }}</ref><ref name="CUTRI">{{Cite journal
    | author=Cutri, R. M.
    | title=2MASS All Sky Catalog of point sources
    | journal=The IRSA 2MASS All-Sky Point Source Catalog, NASA/IPAC Infrared Science Archive.
    | date=June 2003
    | bibcode=2003tmc..book.....C
    | last2=Skrutskie
    | first2=M. F.
    | last3=Van Dyk
    | first3=S.
    | last4=Beichman
    | first4=C. A.
    | display-authors=4
    | last5=Carpenter
    | first5=J. M.
    | last6=Chester
    | first6=T.
    | last7=Cambresy
    | first7=L.
    | last8=Evans
    | first8=T.
    | last9=Fowler
    | first9=J.}}</ref>
| dec = {{DEC|+13|14|48.4}}<ref name="SIMBAD" /><ref name="CUTRI"/>
| dist_ly = 1,500 [[light year|ly]] (460 [[parsec|pc]])<ref name="APOD">{{Cite APOD
  | title=The Medusa Nebula
  | date=12 June 2010
  | access-date=2010-07-01}}</ref>
| appmag_v = 15.99<ref name="SIMBAD" />
| size_v = 10.25 x 10.25 [[minute and second of arc|arcmin]]<ref name="SIMBAD"/>
| constellation  = [[Gemini (constellation)|Gemini]]
| radius_ly = 4 <ref name="APOD"/>
| absmag_v = 7.68
| notes = Very large & very low surface brightness
| names = [[Sharpless catalog|Sharpless]] 2-274, PK 205+14 1, Abell 21 <ref name="SIMBAD" />
}}
{{Sky|07|29|02|+|13|14|15|1000}}
The '''Medusa Nebula''' is a [[planetary nebula]] in the constellation of [[Gemini (constellation)|Gemini]]. It is also known as [[Abell catalogue|Abell]] 21 and [[Sharpless catalog|Sharpless]] 2-274. It was originally discovered in 1955 by [[University of California, Los Angeles]] astronomer [[George O. Abell]], who classified it as an old planetary nebula.<ref name="LOZINSKAYA">{{Cite journal| author=Lozinskaya, T. A.  | title=Interferometry of the Medusa Nebula A21 (YM 29) | journal=Soviet Astronomy  | date=June 1973  | volume= 16  | page=945 | bibcode=1973SvA....16..945L}}</ref> With the computation of expansion velocities and the thermal character of the radio emission, Soviet astronomers in 1971 concluded that it was most likely a planetary nebula.<ref name="LOZINSKAYA"/> As the nebula is so large, its surface brightness is very low, with surface magnitudes of between +15.99 and +25 reported.{{citation needed|date=April 2020}}

The central star of the planetary nebula is an [[PG 1159 star]].<ref>{{cite journal|doi=10.1051/0004-6361/202141916|title=Planetary nebulae in Gaia EDR3: Central star identification, properties, and binarity|year=2021|last1=González-Santamaría|first1=I.|last2=Manteiga|first2=M.|last3=Manchado|first3=A.|last4=Ulla|first4=A.|last5=Dafonte|first5=C.|last6=López Varela|first6=P.|journal=Astronomy & Astrophysics|volume=656|pages=A51|arxiv=2109.12114|bibcode=2021A&A...656A..51G|s2cid=237940344}}</ref>

==See also==
* [[Abell Catalog of Planetary Nebulae]]　　　　　　　　　　　
* [[Geminga]], Gemini gamma-ray source
* [[Gemini in Chinese astronomy]]
* [[IC 444]], reflection nebula
* [[Messier 35]] open cluster
* [[Cancer Minor (constellation)]] - Obsolete constellation inside modern Gemini

==References==
{{Reflist}}

==External links==
*The Sharpless Catalog: [https://web.archive.org/web/20110930102709/http://galaxymap.org/cgi-bin/sharpless.py?s=274 Sharpless 274]
*[[Astronomy Picture of the Day|APOD]] picture: [http://antwrp.gsfc.nasa.gov/apod/ap100612.html The Medusa Nebula]
*Images of the Universe: {{usurped|1=[https://web.archive.org/web/20071129004251/http://www.starimager.com/Image%20Gallery%20Pages/Planetary%20Nebulae/medusa%20nebula.htm PK 205+14.1 The Medusa Nebula in Gemini]}}

{{Sh2 objects}}
{{Stars of Gemini}}
{{Portal bar|Astronomy|Stars|Outer space}}
{{DEFAULTSORT:Medusa Nebula}}
[[Category:Planetary nebulae]]
[[Category:Gemini (constellation)]]
[[Category:Sharpless objects]]
[[Category:Abell planetary nebulae|21]]
[[Category:Astronomical objects discovered in 1955]]

{{nebula-stub}}