Cancer

When and where to look for Cancer

Cancer crosses the meridian — its highest point in the sky — at local midnight around January, which makes the months from December to February the easiest time to find it in the evening. It spans declinations +9.2° to +28.8°, so visible from everywhere north of about 61°S.

The quickest way to find it is to open the live AR sky map and point your phone at the sky — if Cancer is above your horizon right now, its figure is drawn in the position it genuinely occupies above you.

Brightest stars in Cancer

Magnitude runs backwards: lower numbers are brighter, and anything below about 6.5 is beyond the naked eye under a dark sky.

What Cancer is made of

The catalogue lists 102 stars within Cancer, of which 102 are magnitude 6.5 or brighter — the limit of what an unaided eye picks up under a genuinely dark sky. The rest need binoculars or a telescope.

Spectral make-up

Spectral class is a temperature ordering, running from O at around 30,000 K down to M below 3,500 K. A constellation is a direction, not a group, so this is simply what happens to lie along that line of sight.

The closest catalogued star in this direction is Copernicus at 40.3 light years. The most distant is HD 67542 at roughly 1,418 light years — stars that appear side by side here are nothing of the sort.

Deep-sky objects in Cancer

• Beehive Cluster — open cluster

These are marked on the sky map, so you can see where they sit relative to the constellation figure in real time.