Sky Diary

The Sky at Night

Orion is still well placed towards the south during the evenings of February. You may have read recently about Betelgeuse, the bright orange coloured star above the three stars of Orion's belt, having become less bright during the past few months. When I looked at Orion at the beginning of the year I had to agree that it was not as bright as it had been during last winter at about the same time. As its brilliance has faded, the orange colour has become more obvious and it is certainly less bright than Rigel, below Orion's belt. However, John Herschel described changes in brightness between 1836 and 1840 and when Johan Bayer designated it as alpha, the brightest star in Orion, in 1603 it seems likely that it was at its brightest then. It is now know to be an irregularly variable star which expands and contracts as it reaches the end of its life. I am not convinced that this most recent dimming indicates that it will blow up catastrophically as a supernova in the immediate future, although it will certainly do so at some time. But, during February, just to make sure you see Orion as it has been for millennia, have a look at Betelgeuse whenever the sky is clear. If we are fortunate, or unfortunate, to see Betelgeuse become a supernova it will indeed be a spectacular sight, perhaps bright enough to be seen in daylight. Sadly, Orion as we know it would no longer look quite the same after the nova fades.

Follow the three stars of Orion's belt eastwards and you cannot fail to notice the brightest star in the entire sky, with the exception of our Sun, Sirius. Sirius is the brightest star of the much less prominent constellation Canis Major, the greater dog, which together with Canis Minor, the lesser dog, follow Orion through the sky. Sirius is often said to twinkle and change colour and it does this because it is quite low in our sky and its light is subject to distortion in the Earth's atmosphere. The reason that it is so bright is that it is so close to our Sun. It is only 8.6 light years distant, one of the Sun's nearest neighbours, and its white colour emphasises its brightness. Sirius is slowly moving towards the Sun and will be at its brightest in 60,000 years then it will start to move away but will still be our brightest star for the next 210,000 years.

There is a bit of a bare gap in the sky following Gemini until the distinct spring constellation of Leo rises a bit higher in March.

The Planets

Mercury

Mercury

Mercury will be best seen for a few days around the 10th February when it will be quite low in the west-south-west for about an hour after sunset.

Venus

Venus

Venus is so bright that it can't be missed in the south-west shortly after sunset and setting itself at around 9pm.

Mars

Mars

Mars rises at about 5am and will be seen low in in the south-south-east until it fades in the brightening sky.

Jupiter

Jupiter

Jupiter rises at around 6am, following Mars, and will be seen briefly until it suffers the same fate as Mars.

Saturn

Saturn

Saturn rises after Jupiter at about 7am but will not be visible because of the rising Sun.

The Moon

The Moon

The Moon is at first quarter on the 2nd, full on the 9th, at last quarter on the 15th and new on the 23rd February.

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