Messier 103 (also known as M103, or NGC 581) is an

open cluster An open cluster is a type of star cluster made of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. More than 1,100 open clusters have been discovered within the Milky Way galaxy, and ...

where a few hundred, mainly very faint, stars figure in Cassiopeia. It was discovered in 1781 by

Charles Messier Charles Messier (; 26 June 1730 – 12 April 1817) was a French astronomer. He published an astronomical catalogue consisting of 110 nebulae and star clusters, which came to be known as the ''Messier objects''. Messier's purpose f ...

's friend and collaborator

Pierre Méchain Pierre François André Méchain (; 16 August 1744 – 20 September 1804) was a French astronomer and surveyor who, with Charles Messier, was a major contributor to the early study of deep-sky objects and comets. Life Pierre Méchain was bo ...

.Robert Bruce Thompson

''M103 (open cluster in Cassiopeia). Accessed online 13 April 2011 It is located between 8,000 to 9,500

light-year A light-year, alternatively spelled light year, is a large unit of length used to express astronomical distances and is equivalent to about 9.46 trillion kilometers (), or 5.88 trillion miles ().One trillion here is taken to be 101 ...

s from the

Solar System The Solar System Capitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar ...

and ranging over about 15 light years. It holds about 40 certain-member stars, two of which have magnitudes 10.5, and a 10.8 red giant, which is the brightest within the cluster. A bright known foreground object is the star Struve 131, not a member of the cluster. The cluster may have 172 stars if including those down to 50% probability of a gravitational tie. M103 is about 22 million years old.

Observation history

After the discovery of

Messier 101 #REDIRECT Pinwheel Galaxy 101 101 may refer to: * 101 (number), the number * AD 101, a year in the 2nd century AD * 101 BC, a year in the 2nd century BC It may also refer to: Entertainment * ''101'' (album), a live album and documentary by D ...

through 103, Messier had no cause to carry out more detailed observations of these clusters and included them as an addition to his catalogue using the data of Méchain. In 1783,

William Herschel Frederick William Herschel (; german: Friedrich Wilhelm Herschel; 15 November 1738 – 25 August 1822) was a German-born British astronomer and composer. He frequently collaborated with his younger sister and fellow astronomer Carolin ...

observed M103 and described the region as 14 to 16 ''pL'' (pretty large stars) and with great many ''eS'' or extremely faint ones.

Åke Wallenquist Åke Anders Edvard Wallenquist (January 16, 1904 – April 8, 1994) was a Swedish astronomer. He worked at the Dutch Bosscha Observatory in Indonesia between 1928 and 1935, and became assistant professor at Uppsala's Kvistabergs Observatoriu ...

then identified 40 stars in M103 while

Antonín Bečvář Antonín Bečvář (; 10 June 1901 – 10 January 1965) was a Czech astronomer who was active in Slovakia. He was born (and died) in Stará Boleslav. Among his chief achievements is the foundation of the Skalnaté Pleso Observatory and the ...

raised the number to 60. Archinal and Hynes then determined that the cluster had 172 stars. Admiral William Henry Smyth was the first to see the 10.8-magnitude red giant, citing the double star on Cassiopeia's knee, about a degree to the northeast of Delta Cassiopeiae (Ruchbah/Rukhbah).

Observing with binoculars

Messier 103 has been rated by the Astronomical League as an easy object to find and the cluster is visible even with the use of binoculars. M103 can be seen as a nebulous fan-shaped patch, and takes up about a 6 arcminute′ circle (a tenth of a degree), about a fifth the apparent diameter of the moon. To find M103, it is suggested that the observer center their binoculars on Ruchbah or the bottom left (or right against a northern horizon, as it more often is from Earth) star of the signature “W” asterism of Cassiopeia. The cluster will appear as a hazy patch about of a field/line toward

Epsilon Cassiopeiae Epsilon Cassiopeiae or ε Cassiopeiae, officially named Segin (), is a single star in the northern constellation of Cassiopeia. With an apparent visual magnitude of 3.4, this is one of the brightest stars in the constellation. The dista ...

, a northern endpoint of the W, on the outer side of the W.

Gallery

File:NGC 0581 DSS.jpg, M103 image from Aladin Sky Atlas File:M103map.png, Finder chart for M103

References and footnotes

External links

Open Cluster M103 @ SEDS Messier pages
* * {{Sky, 01, 33.2, 00, +, 60, 42, 00, 8500 Open clusters Cassiopeia (constellation)

103 103 may refer to: *103 (number), the number *AD 103, a year in the 2nd century AD *103 BC, a year in the 2nd century BC *103 (Tyne Electrical Engineers) Field Squadron, a territorial regiment * 103 (Newcastle) Field Squadron, Royal Engineers *103 (L ...

Messier 103 178104?? Perseus Arm Discoveries by Pierre Méchain

Observation history

Observing with binoculars

Gallery

See also

References and footnotes

External links