Welcome to the February night sky. During the cold clear nights of this month, the grand constellation of Orion “the Hunter” dominates the early evening sky.
The three stars that make up the famous Belt of Orion are easy to identify and are situated exactly on the equator of the heavens and, therefore, visible all over the world at this time of the year. These three stars are all much younger than the Sun at just a few million years old.
They are all dozens of times more massive than the sun, hundreds of times the volume and thousands of times the brightness. These young blue giant stars will have a much shorter lifespan than our Sun and will explode as a Supernova at the end of their lives.
The three Belt stars from left to right are named: Alnitak, Alnilam and Mintaka. The centre star is of special interest as it is a single star unlike the other two that are multiple star systems. This means that it could have orbiting planets. These possible planets would be much too young to sustain complex life. It would be difficult for human beings to travel to Alnilam as it is nearly 1,400 light years away.
Following the line of the three Belt stars downward and to the left, we arrive at the brightest star in the night-time sky called Sirius “the Dog Star”. Sirius is so bright because it is intrinsically 25 times more luminous than the Sun and relatively close to us at 8.6 light years away.
This star is also relatively young in stellar terms and, early on in its life, it was, in fact, a double star with another slightly larger giant blue star orbiting. The more massive of the two evolving quickly towards the end of its life by changing into a red giant and then to a white dwarf.
A similar fate awaits our own Sun in about five billion years. The white dwarf in the Sirius system has about the same diameter of the Earth but the mass of our Sun. It is now just visible close to Sirius by using a large telescope and with good seeing conditions.
There are no major meteor showers in February and the bright planets are quite close to the Sun with Venus visible only in the early morning close to the much fainter planet Mars. The gas giant planet Jupiter is still a bright evening object, but it is rapidly lost in the twilight. Saturn is in conjunction with the Sun and not visible.
The Moon is new on the 1st, first quarter on the 8th, full on the 16th and last quarter on February 23.
By Clive Jackson
Clive Jackson is the director of the Camera Obscura attraction (next to the Castle in Tavira), specialising in education and public outreach.
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To see the February Sky Map click on the pdf link below