Sky Diary

I have not mentioned the well-known constellation, Orion, this winter. Most people will know and perhaps recognise Orion with the three bright stars forming his belt, the orange giant star, Betelgeuse, above the belt and the blue supergiant star, Rigel, below. Orion can easily be imagined as a figure and was one of the original 28 constellations listed by Ptolemy, and named after a hunter in Greek mythology. Orion sits towards the south during February evenings and is well worth a look with binoculars. Just below Alnitak, the left hand star of Orion’s belt, there is a less bright line of stars which represents his sword. If you look at the centre of the sword you will see a diffuse glowing patch. This is the Great Orion Nebula, numbered 42 in Charles Messier’s catalogue. It is an interstellar cloud of gas and dust about 1,300 light years distant and which is actively forming young stars. The young stars are making the nebula glow and four of these bright stars can be seen to be emerging from the nebulosity. Because of the shape they form they are known as the Trapezium and can easily be seen with quite a small telescope. There are likely to be many young stars still hidden by the gas and dust but which will emerge in millions of years as a star cluster when the remaining material is used up. A large area of Orion is covered by a fainter molecular cloud which can’t be seen but shows on long exposure photographs. Among the interesting features is a dark nebula close to the star Alnitak which is known as the Horse Head Nebula. Of local interest, this was discovered in 1888 on a photographic plate by the Dundee astronomer Williamina Fleming when she was working at Harvard College Observatory.

The winter constellations Gemini, Auriga and Perseus are strung out high in the sky from south to south-west while Pegasus is descending towards the horizon in the north-west. Already in February the area of sky towards the south-east and east is showing the characteristics of late winter into spring. There are fewer bright stars in this area with the fainter constellation of Cancer and Hydra filling this part of the sky. However, one clearly identifiable constellation, Leo is rising from the east and will provide interest during spring.

There will be an annular solar eclipse on the 17th February, but it will only be visible in the Antarctic. We will have more luck on 12th August when there will be a 90% partial solar eclipse when maximum will be visible at 7pm if the sky is clear.

_{Sky Notes courtesy of Ken Kennedy of Dundee Astronomical Association}