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Constellation Cancer

Cancer is located on the ecliptic between the constellations Gemini and Leo. The only requirement to see the constellation and acquire the objects, is having a dark enough sky. The brighter stars of Cancer are dim but visible on a clear evening. A pair of binoculars might be helpful in locating the objects but not necessarily required.

Praesepe / Beehive Cluster / The Manger / The Crib / M44 / NGC 2632

This is a galactic cluster in Cancer. Location RA 08h 40m, Dec +19° 59'; Diameter 95'; Visual magnitude 3.1; Distance about 160 parsecs or 520 light-years; Age about 650 million years old. This cluster is also called the Beehive Cluster. It has the catalog designations of M44 and NGC 2632. This is a typical galactic cluster. It contains bright, but short-lived type O and B stars. Galactic clusters are always found in the plane of the galaxy, embedded in the spiral arms. All of the stars in a galactic cluster are believed to be formed around the same time and therefore are the same age. Galileo was the first to study the object with a telescope and observe that this "fuzzy patch" was actually composed of many stars. To locate Praesepe locate delta Cancri, at the center of the constellation. Then find gamma Cancri to the north, eta Cancri to the west, and theta Cancri to the south. These stars form a box which contains the cluster, called epsilon Cancri. Praesepe is also called the Manger, or the Crib. The stars gamma and delta Cancri are known as "the assess", or "the donkeys".

Comparing the young and the old: When viewed using two adjacent telescopes, M44 and M67 can illustrate the life of a galactic cluster. M44 and its ball-shaped cluster of bright stars show the early life, with all of its young stars close together. M67 and its elongated cluster demonstrates how the stars are influenced by the gravity of other objects within the galactic plane and eventually lose their identity as a cluster.

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M67 / NGC 2682

This is a galactic cluster in Cancer. Location RA 08h 51m, Dec +11° 49'; Diameter 30', Visual magnitude 6.9; Distance 830 parsecs or 2,706 light-years; Age over 10 billion years old. This cluster is designated M67 and NGC 2682. Binoculars can resolve this object, but telescopes with an aperture of 6 or 8 inches show it in great detail. Galactic clusters are always found in the plane of the galaxy, embedded in the spiral arms. All of the stars in a galactic cluster are believed to be formed around the same time and therefore are the same age.  This cluster is elongated in an east-west direction and there is a dark space in the middle near the eastern end. M67 is known as one of the oldest open clusters. Its stars are older main sequence types, some of which have passed the red giant stage. To locate M67 find alpha Cancri and move just a bit westward.

Comparing the young and the old: When viewed using two adjacent telescopes, M44 and M67 can illustrate the life of a galactic cluster. M44 and its ball-shaped cluster of bright stars show the early life, with all of its young stars close together. M67 and its elongated cluster demonstrates how the stars are influenced by the gravity of other objects within the galactic plane and eventually lose their identity as a cluster.

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James M. Thomas, last updated October 14, 1999.

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