View source for Messier 103

{{Short description|Open cluster in the constellation Cassiopeia}}
{{Use dmy dates|date=March 2019}}
{{Infobox open cluster
| name=Messier 103
| image=[[Image:M103 Mazur.jpg|300px]]
| caption=Open cluster Messier 103 in Cassiopeia
| epoch=[[J2000.0]]
| class=d
| ra={{RA|01|33.2}}
| dec={{Dec|+60|42}}
| dist_ly=9,400 [[light-year]]s
| dist_pc= 2.884 ± 0.313 [[Parsec#Parsecs_and_kiloparsecs|kpc]]<ref name="aaa349" />
| appmag_v=7.4<ref>{{cite web |url=https://messier.seds.org/m/m103.html |title=Messier 103 |access-date=30 April 2022 |website=SEDS Messier Catalog}}</ref>
| size_v=6.0'
| mass_kg=
| mass_msol=
| radius_ly=
| v_hb=
| age=12.6 ± 0.2 million years<ref name="aaa349" />
| notes=
| names=NGC 581, [[Collinder catalogue|Cr]] 14
}}

'''Messier 103''' (also known as '''M103''', or '''NGC 581''') is a small [[open cluster]] of many faint stars in [[Cassiopeia (constellation)|Cassiopeia]]. It was discovered on 27 March 1781 by [[Pierre Méchain]], but later added as [[Charles Messier]]'s last deep-sky object in his catalogue.<ref name="TTGNet">Robert Bruce Thompson  [http://www.ttgnet.com/astronomy/winter-messier-program/m103.html], ''M103 (open cluster in Cassiopeia). Accessed online 13 April 2011''</ref> 

It is located 9,400 [[light-year]]s from the [[Sun]]<ref name="aaa349">
{{cite journal
|author=Sanner, J. |author2=Geffert, M. |author3=Brunzendorf, J. |author4=Schmoll, J.
|date=1999
|title=Photometric and kinematic studies of open star clusters. I. NGC 581 (M 103)
|journal=[[Astronomy and Astrophysics]]
|volume=349|pages=448–456
|bibcode=1999A&A...349..448S
|arxiv = astro-ph/9908059 }}</ref><ref name="TTGNet" /> and is about 15 light years across. It holds two prominent stars, of which the brightest is magnitude 10.5, and in the center of the cluster, another magnitude 10.8 red giant. Another bright foreground object is the double star Struve 131,<ref name="seds">{{Cite web|title= Messier 103: Observations and Descriptions  |work=SEDS |url= http://messier.seds.org/m/m103.html| access-date=2011-04-13}}</ref> but is not a member of the cluster. Cluster membership is about 172 stars based on >50% probability of gravitational attachment that binds the cluster together.<ref name="seds" /> M103 is between 12.6<ref name="aaa349" /> to 25 million years<ref name="apj722">
{{cite journal
|author=Huang, W|author2=Gies, D.R. |author3=McSwain, M.V.
|date=2010
|title=A stellar rotation census of B stars: from ZAMS to TAMS
|journal=[[Astrophysical Journal]]
|volume=722|pages=605–619
|doi=10.1088/0004-637X/722/1/605 |bibcode=2010ApJ...722..605H
|arxiv = 1008.1761|s2cid=118532653 }}</ref> in age.

==Observation history==
After the discovery of [[Messier 101]] through 103 by [[Pierre Méchain]], Messier later added this open cluster  to his own catalogue.<ref name="seds" /><ref>{{cite web|title=3 Clusters in Cassiopeia|url=http://www.oneminuteastronomer.com/2009/11/05/3-clusters-cassiopeia/|work=One Minute Astronomer|access-date=2010-04-14|archive-url=https://web.archive.org/web/20110222063152/http://www.oneminuteastronomer.com/2009/11/05/3-clusters-cassiopeia/|archive-date=22 February 2011|url-status=dead}}</ref> In 1783, [[William Herschel]] described the region of M103 as 14 to 16 ''pL'' (pretty large stars) and with great many ''eS'' or extremely faint ones.<ref>{{cite web|title= Messier 103|url= http://www.universetoday.com/49854/messier-103/|work=Universe Today| access-date=2010-04-14|date= 2010-01-07}}</ref> [[Åke Wallenquist]] first identified 40 stars in M103 while [[Antonín Bečvář]] raised this to 60. Archinal and Hynes suggest that the cluster has 172 stars.<ref name="seds" /> [[William Henry Smyth|Admiral William Henry Smyth]] pointed out the cluster's 10.8-magnitude red giant, citing it was a double star on Cassiopeia's knee, about 1° northeast of [[Delta Cassiopeiae]], sometimes called as Ruchbah or Rukhbah.

==Telescopic view==
Messier 103 is an easy object to find and the cluster is visible in binoculars or a small telescope.<ref>{{cite web|title=Messier 103|url=http://www.perezmedia.net/beltofvenus/archives/000373.html|work=Perez Media|access-date=2010-04-14}}</ref><ref name="seds" /><ref>{{cite web|title=The Constellation Cassiopeia|url=http://www.zimbio.com/Andromeda+Galaxy/articles/7acHFHcKLjm/The+Constellation+Cassiopeia|work=Zimbio|access-date=2010-04-14|url-status=dead|archive-url=https://web.archive.org/web/20121011200151/http://www.zimbio.com/Andromeda+Galaxy/articles/7acHFHcKLjm/The+Constellation+Cassiopeia|archive-date=11 October 2012}}</ref> M103 can be seen as a nebulous fan-shaped patch, and is about a fifth the apparent diameter of the Moon or 6 arcminute (6′) or 0.1° across. To find M103, it is suggested that the observer center on Ruchbah or the lowest star of the signature “W” asterism of Cassiopeia. The cluster will appear as a hazy patch in a field about {{frac|1|3}} the length of an imaginary line towards [[Epsilon Cassiopeiae]], a northern endpoint of the 'W', and placed on the outer side of the 'W'.

==Gallery==
<gallery>
File:NGC 0581 DSS.jpg|M103 image from Aladin Sky Atlas
File:M103map.png|Finder chart for M103
</gallery>

==See also==
* [[List of Messier objects]]

==References and footnotes==
{{reflist|colwidth=30em}}
{{notelist}}

==External links==
{{commons category}}
*[http://messier.seds.org/m/m103.html Open Cluster M103 @ SEDS Messier pages]
*[https://observing.skyhound.com/archives/nov/M_103.html Open Cluster M103 @ Skyhound.com]
*{{APOD |date=7 February 2001|title=Distant Open Cluster M103}}{{Sky-Map.org}}

{{Portal bar|Astronomy|Stars|Outer space}}
{{Astronomical catalogs|NGC=581|M=103}}
{{Messier objects}}
{{NGC objects:500-999}}
{{Cassiopeia (constellation)}}

{{Sky|01|33.2|00|+|60|42|00|8500}}

[[Category:Open clusters]]
[[Category:Cassiopeia (constellation)]]
[[Category:Messier objects|103]]
[[Category:NGC objects|Messier 103]]
[[Category:Astronomical objects discovered in 1781|178104??]]
[[Category:Perseus Arm]]
[[Category:Discoveries by Pierre Méchain]]