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Collinder Catalogue

'Cr' Catalogue

A catalogue of nearly five hundred celestial objects, published by Per Collinder as an appendix to his 1931 paper On structural properties of open galactic clusters and their spatial distribution. The catalogue is primarily dedicated to listing open clusters, groups of stars within the galactic disc that share a common origin and remain bound together by gravitational forces.

Objects within the catalogue are given numbers in the form 'Collinder 42' (an example that refers to the Pleiades in Taurus). Though the full name 'Collinder' is preferred in references, the abbreviation 'Cr' remains relatively common, and the rarer short form 'Col' is also occasionally seen.

The full Collinder Catalogue lists a total of 471 objects. Of these, 452 are recognised as belonging to actual open clusters, while the remaining nineteen are now considered to fall outside that classification. Of these other nineteen listed objects, eleven are globular clusters rather than open clusters, while several others are now seen as asterisms rather than true clusters (that is, groups of stars that merely appear to be clustered due to their line of sight from Earth). In a handful of cases (such as that of Collinder 269 in Musca), the status of the object still remains uncertain.

Collinder 173 is one of the brightest and most extensive clusters in the Collinder Catalogue, extending across a region of the sky some six degrees in diameter (or about twelve times the size of the Moon's disc). The cluster falls on the border between the constellations Vela and Puppis, and lies an estimated 1,350 light years from the Sun. Imagery provided by Aladin sky atlas

The clusters within the catalogue range from the prominent and familiar to the faint and obscure. The catalogue lists, for example, bright clusters like the Pleiades and Hyades in Taurus (Collinder 42 and Collinder 50, respectively) and the stars clustered around Orion's Belt (Collinder 70). At the other end of the scale, the faintest object in the list is Collinder 404, a fifteenth-magnitude cluster associated with the nebula NGC 6820 in Vulpecula. (Collinder 404's apparent magnitude of +14.9 means that the faintest cluster in the list is nearly 600,000 times fainter than the brightest, the magnitude +1.5 Pleiades.)

The selective list below summarises some of the better-known or most prominent clusters to be included within the Collinder Catalogue. For a fuller list, see the 'Collinder Catalogue' section of the Star Clusters index page.

Cr 24 / Cr 25Double ClusterA pair of clusters close together in the sky, also known as the Sword Handle in Perseus. Collider 24 refers to the component cluster h Persei, while Collinder 25 identifies its neighbour Chi Persei.
Cr 39Alpha Persei ClusterA broad and loose grouping of stars around the second-magnitude Mirfak or Alpha Persei.
Cr 42PleiadesOne of the most prominent clusters in the sky, and easily visible to the naked eye, the Pleiades or Seven Sisters lie in the northwestern parts of Taurus the Bull.
Cr 50HyadesThe nearest open cluster to the Solar System, the stars of the Hyades form a roughly triangular shape representing the 'face' of Taurus.
Cr 69Lambda Orionis ClusterA cluster grouped around the O-type star Meissa or Lambda Orionis, marking the 'head' of the constellation Orion.
Cr 70Orion's BeltA group of nearly a hundred stars, with by far the three brightest members being Alnitak, Alnilam and Mintaka, the stars that form Orion's Belt.
Cr 135Pi Puppis ClusterA grouping of several thousand stars around the orange supergiant Pi Puppis (otherwise known as Ahadi) in the central regions of the constellation Puppis.
Cr 189PraesepeAlso called the Beehive Cluster or M44, this object in central Cancer is one of the nearer open clusters to the Sun.
Cr 229Southern PleiadesA bright cluster of blue stars centred around Vathorz Posterior or Theta Carinae (and sometimes called the Theta Carinae Cluster).
Cr 238Wishing Well ClusterA busy star cluster falling against the dense background of the Milky Way as it runs through eastern Carina.
Cr 256Coma Berenices ClusterIn the northwestern parts of Coma Berenices, this is a relatively nearby open cluster at a distance of less than three hundred light years from the Sun.
Cr 264Jewel BoxA distant open cluster centred around the supergiant Kappa Crucis (and so sometimes called the Kappa Crucis Cluster) near the star Mimosa in the constellation of the Southen Cross.
Cr 302Upper Scorpius AssociationAlso called the Antares Cluster, this collection of stars around red Antares in Scorpius is formally a stellar association rather than an open cluster.
Cr 354Ptolemy's ClusterA bright open cluster near the tail of Scorpius, known since classical times, and also classified as Messier 7.
Cr 399CoathangerAn asterism rather than a true open cluster, the Coathanger (otherwise known as Brocchi's Cluster or Al Sufi's Cluster) describes a distinctive linear grouping of stars in Vulpecula.

Comparable in many ways to the Collinder Catalogue is the earlier index of star clusters known as the Melotte Catalogue. The Melotte list is more inclusive than the Collinder Catalogue, incorporating many globular clusters as well as open clusters, but it also rather less extensive, containing just 245 objects as compared with the Collinder Catalogue's 471. Both these catalogues include many of the brighter clusters in the sky, and so there is a considerable degree of overlap between the two systems. It is not uncommon, especially for more prominent clusters, to see both a Collinder number and a Melotte number referring to the same object. So, for example, as well as being listed as 'Collinder 42', the Pleiades are also designated 'Melotte 22'.


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