WINTER (NORTHERN HEMISPHERE)
The Winter skies are particularly striking in the Northern Hemisphere
because they are long, become really dark in mid-latitudes and are
graced by two of the most distinctive patterns in the night sky – the
Plough or Big Dipper, and Orion, the Hunter. From mid-latitudes, the
seven stars that make up the pattern of the Plough, are circumpolar,
meaning that they never set.Orion, the Hunter
The stars of Orion are actually brighter than those of Ursa Major. The two leaders,
Betelgeux and Rigel are not alike. Rigel is brilliant white and at least 40,000 times
as luminous as the Sun, whereas Betelgeux is a huge red supergiant. It is not
as luminous as Rigel, but at least 15,000 times as powerful as the Sun and is of
immense size. Like so many red supergiants it is decidedly variable, and at its
best it will become nearly as brilliant as Rigel, though for most of the time it is
half a magnitude fainter. Orion has three bright stars making up the Hunter’sThe constellation Ursa Major is invaluable as a guide to other constellations.
In the southern part of the sky we see Orion the Hunter, which is also of
immense value in identifying other constellations. Unlike Ursa Major, Orion is
not circumpolar but when above the horizon is quite unmistakeable.
Come first to Ursa Major with its seven main stars. Two of these, Merak
and Dubhe, show the way to Polaris in Ursa Minor, the Little Bear, which is of
the second magnitude and very close to the North Celestial Pole. This means
that it's of middle brightness and hardly seems to move at all.1Astronomer Book