View source for Astronomy:NGC 663

{{short description|Open star cluster in the constellation Cassiopeia}}
{{Infobox cluster
| name = [[Astronomy:New General Catalogue|NGC]] 663
| image = [[File:NGC663HunterWilson.jpg|250px]]
| caption= NGC 663 in Cassiopeia
| constellation = [[Astronomy:Cassiopeia (constellation)|Cassiopeia]]
| epoch = [[Astronomy:J2000|J2000]]
| class = -
| ra = 01<sup>h</sup>&nbsp;46.0<sup>m</sup>
| dec = +61° 15{{prime}}
| dist_ly = 6,850 [[Light year|ly]]
| dist_pc = 2,100 [[Astronomy:Parsec|pc]]
| appmag_v = 7.1
| size_v = 16.0{{prime}}
| mass_kg =
| mass_msol =
| radius_ly =
| v_hb =
| age =
| notes =
| names = [[Astronomy:Caldwell catalogue|Caldwell]] 10, [[Astronomy:Collinder catalogue|Cr]] 20
}}
'''NGC 663''' (also known as '''[[Astronomy:Caldwell catalogue|Caldwell]] 10''') is a young [[Astronomy:Open cluster|open cluster]] in the constellation of Cassiopeia. It has an estimated 400 stars and spans about a quarter of a degree across the sky. It can reportedly be detected with the unaided eye, although a telescope is recommended for best viewing. The brightest members of the cluster can be viewed with binoculars. Although the listed visual magnitude is 7.1, several observers have reported higher estimates.<ref>
{{cite book
 | last=O'Meara | first=S. J.
 | date=2002
 | title=The Caldwell objects, Deep-sky companions
 | publisher={{wipe|Cambridge University Press}}
 | pages=50&ndash;51
 | isbn=978-0-521-82796-6
}}</ref>

After adjusting for reddening due to interstellar dust, the [[Physics:Distance modulus|distance modulus]] is estimated as 11.6 magnitudes. It is located about 2,100 parsecs distant with an estimated age of 20&ndash;25 million years.<ref name="aaa376">
{{cite journal
 | author=Pigulski, A.
 | author2=Kopacki, G.
 | author3=Kolaczkowski, Z.
 | date=2001
 | title=The young open cluster NGC 663 and its Be stars
 | journal=Astronomy & Astrophysics
 | volume=376 | issue=1 | pages=144–153
 | bibcode=2001A&A...376..144P
 | doi=10.1051/0004-6361:20010974
| doi-access=free
 }}</ref> This means that stars of spectral class B2 or higher (in the sense of higher mass), are reaching the end of their [[Astronomy:Main sequence|main sequence]] lifespan.<ref name="marco_et_al_2005">
{{cite journal
 | author=Marco, A.
 | author2=Negueruela, I.
 | author3=Motch, C.
 | date=2007
 | title=Blue Stragglers, Be Stars and X-ray Binaries in Open Clusters
 | journal=ASP Conference Series
 | volume=361 |pages=388
 | bibcode=2007ASPC..361..388M
 }}</ref> This cluster appears to be located in front of a [[Astronomy:Molecular cloud|molecular cloud]], although the two are not physically associated. This cloud has the effect of blocking background stars from the visual image of the cluster as it lies at a distance of 300 parsecs.<ref>
{{cite journal
 | author=Phelps, Randy L.
 | author2=Janes, Kenneth A.
 | date=1993
 | title=Young open clusters as probes of the star-formation process. 2: Mass and luminosity functions of young open clusters
 | journal=Astronomical Journal
 | volume=106 | issue=5 | pages=1870–1884
 | bibcode=1993AJ....106.1870P
 | doi=10.1086/116772
}}</ref>

This cluster is of interest because of the high number of [[Astronomy:Be star|Be star]]s, with a total of about 24 discovered. These are spectral class B stars that show prominent emission lines of [[Chemistry:Hydrogen|hydrogen]] in their spectrum. Most of the Be stars in the cluster lie between spectral class B0 and B3.<ref name="aaa376"/> A candidate member of the cluster, LS I +61° 235, is a Be star with an [[Physics:X-ray|X-ray]] binary component that has a period of about three years.<ref>{{cite journal
 | author=Reig, P.
 | display-authors=4
 | author2=Fabregat, J.
 | author3=Coe, M. J.
 | author4=Roche, P.
 | author5=Chakrabarty, D.
 | author6=Negueruela, I.
 | author7=Steele, I.
 | date=1997
 | title=The Be/X-ray binary LS I +61 235/RX J0146.9+6121: physical parameters and V/R variability
 | url=http://aa.springer.de/papers/7322001/2300183.pdf
 | journal=Astronomy and Astrophysics
 | volume=322
 | issue=1
 | pages=183–192
 | bibcode=1997A&A...322..183R
 | access-date=2012-04-17
 | archive-url=https://web.archive.org/web/20160304050941/http://aa.springer.de/papers/7322001/2300183.pdf
 | archive-date=2016-03-04
 | url-status=dead
 }}</ref> There are at least five [[Astronomy:Blue straggler|blue straggler]]s in the cluster. These are stars that formed by the merger of two other stars.<ref name="marco_et_al_2005"/> Two of the cluster's star systems are likely [[Astronomy:Eclipsing binary|eclipsing binaries]] with periods of 0.6 and 1.03 days.<ref>
{{cite journal
 | last=Pietrzynski | first=G.
 | date=1996
 | title=Variable Stars in the Young Open Cluster NGC 663
 | journal=[[Astronomy:Acta Astronomica|Acta Astronomica]]
 | volume=46 | pages=357–360
 | bibcode=1996AcA....46..357P
}}</ref> NGC 663 also has two [[Astronomy:Red supergiant|red supergiant]] stars, both located on its periphery<ref name="aaa485">{{cite journal
 | author=Mermilliod, J. C.
 | author2=Mayor, M.
 | author3=Udry, S.
 | title=Red giants in open clusters. XIV. Mean radial velocities for 1309 stars and 166 open clusters
 | journal=Astronomy & Astrophysics 
 | volume=485
 | issue=1
 | pages=303–314 
 | date=2008
 | doi=10.1051/0004-6361:200809664
| bibcode=2008A&A...485..303M| citeseerx=10.1.1.30.7545}}</ref><ref name="mnras2005">{{cite journal
 | author=Pandey, A. K.
 | display-authors=4
 | author2=Upadhyay, K.
 | author3=Ogura, K.
 | author4=Sagar, Ram
 | author5=Mohan, V.
 | author6=Mito, H.
 | author7=Bhatt, H. C.
 | author8=Bhatt, B. C.
 | title=Stellar contents of two young open clusters: NGC 663 and 654
 | journal=[[Organization:Monthly Notices of the Royal Astronomical Society|Monthly Notices of the Royal Astronomical Society]] 
 | volume=358
 | issue=4
 | pages=1290–1308 
 | date=2005
 | doi=10.1111/j.1365-2966.2005.08784.x
| bibcode=2005MNRAS.358.1290P| doi-access=free
 }}</ref>

The star cluster is assumed to form part of the [[Astronomy:Stellar association|stellar association]] Cassiopeia OB8, that is located in the Perseus arm of the [[Astronomy:Milky Way|Milky Way]], along with the open clusters [[Astronomy:Messier 103|M103]], [[Astronomy:NGC 654|NGC 654]], [[Astronomy:NGC 659|NGC 659]], and some [[Astronomy:Supergiant|supergiant]] stars scattered between them, all of them having similar ages and distances.<ref name="aaa528">{{cite journal
 | author=Negueruela, I.
 | author2=González-Fernández, C.
 | author3=Marco, A.
 | author4=Clark, J. S.
 | title=A massive association around the obscured open cluster RSGC3
 | journal=Astronomy & Astrophysics 
 | volume=528
 | pages=A59
 | date=2011
 | doi=10.1051/0004-6361/201016102
 | bibcode=2011A&A...528A..59N|arxiv = 1102.0028 | s2cid=53517711
 }}</ref><ref name="ApJS1978">{{cite journal
 | author=Humphreys, R. M.
 | title=Studies of luminous stars in nearby galaxies. I. Supergiants and O stars in the Milky Way.
 | journal=Astrophysical Journal Supplement Series 
 | volume=38
 | pages=309–350 | date=1978
 | doi=10.1086/190559
 | bibcode=1978ApJS...38..309H}}</ref>

==Image gallery==
{{Gallery|width=200
|File:NGC663 - Open Cluster in Cassopeia.jpg|NGC663 LRGB Using PlaneWave CDK 12.5 from Talent, OR
}}

==References==
{{Reflist|30em}}

==External links==
* {{WikiSky}}


{{Caldwell catalogue}}
{{Sky|01|46|16|+|61|13|06|6400}}

{{DEFAULTSORT:NGC 0663}}
[[Category:Open clusters]]
[[Category:Cassiopeia (constellation)]]
[[Category:NGC objects|0663]]
[[Category:Caldwell objects|010b]]

{{Sourceattribution|NGC 663}}