Cancer the Crab is a visually difficult constellation. It is the fourth sign of the zodiac, which means that this is the fourth constellation that the Sun is in a year.
Within the boundaries of Cancer lies the mesmerising cluster, the Beehive. Other objects include obscure galaxy clusters and planetary nebulae.
Appearing as a mysterious hazy cloud to ancient peoples, the Beehive was known since antiquity because it was visible with the naked eye. Only until 1610 was its true nature unveiled when Galileo (discoverer of four Jupiter moons) observed it with a small aperture telescope. It contains a grand total of 350 stars and is also commonly referred to as the Praesepe.
For those who wish to torture their eyes, try finding the background galaxies that shine at a wonderfully faint magnitude of 16.
|The mildly fainter cousin of the Beehive, M67 is very old at an age of roughly 4 billion years. Many of its 500 stars are also this age and the younger stars are are only a few hundred million years old.|
|Abell 31 is an obscure and mostly unknown planetary nebula due to being visible at a time when galaxies are the main attraction.|
|Image copyright D. Salman|
|This face on galaxy has a large yellow core region that is unexpectedly smooth and is surrounded by a detailed pattern of spiral arms. Star formation seems to occur only in the spiral arms and not in the core. There are many background galaxies in the vicinity of this fascinating tightly wound spiral galaxy.|
|This is a fairly large planetary nebula with the common bi-coloured shell of gas. The outer parts are red and the inner parts are blue. The colours are slightly reminiscent of PK 164+31.1 in the constellation Lynx. It also has a very faint outer halo that extends for a considerable distance. It is also commonly referred to as PK 219+31.1 by some published star atlases and is also known as Sh2-290.|
|An interacting duo of galaxies that lie at the faraway distance of 300 million light years away. Both galaxies have streamers of gas that are similar to the ones found in the Antennae Galaxy in Corvus. A very large telescope (preferably a professional observatory such as Cerro Tololo in Chile) is required to view this fascinating pair. Since the pair is interacting, Halton Arp felt that it matched the criteria for inclusion in his atlas of peculiar galaxies at number 243.|
|The infinitesimal distance of 600 million light years is the distance to this galaxy cluster. It contains mainly ellipticals because of interactions between its members that have stripped away gas and material. These interactions must have happened a few billion years ago as we see Abell 671 as it looked 600 million years ago!|