Pensford Field Night Sky, January to February 2010

Pensford Field is a good place in Kew to escape local pollution thrown up by street lighting  and security lights. You can't escape the overall glow of London but on a clear night you can see the brighter stars; with binoculars you can see hundreds more. 

The 5 bright stars of Orion are in the south (over Atwood Avenue) at about 9pm at the end of January, 8pm at the middle of February. Start by locating the three stars of his belt, equally spaced in a straight line. At right angles to the belt are the other two; stretch your arm in front of you and they are a fist above and below the belt. The higher one is Betelgeuse, the lower, Rigel; the latter is as bright as 60,000 suns but much further away - the light from the sun takes 10 minutes to get here, the light from Rigel 900 years.

Look a long way to the left along the line of the belt; low down in the sky is Sirius, the brightest star visible from our latitude on earth. Sirius is in the southern hemisphere of the sky, below the 'celestial equator'; we can only see it in the winter months.

Now look for another bright star, Procyon. It is higher up in the sky, the same distance from Sirius and Betelgeuse as they are from each other; so these three bright stars form a huge prominent equilateral triangle. Overhead near the zenith is Capella, a 'circumpolar' star, visible throughout the year.

Go back to Orion's belt and spot the fuzzy nebula, a knuckle or so below the left star of the belt towards Rigel, known as M42. Nebulae are a sort of star dust, maybe stars in the making. M42 is part of our home galaxy of stars and therefore not all that far away, 1500 light-years compared with about 200,000 light-years for our nearest neighbouring galaxy. A light-year is the distance travelled by light in a year at a speed of 186,000 miles per second.

Now find the 'heavenly twins', Castor and Pollux; they are on a line from Rigel to Betelgeuse in Orion, about 3 fists further on. Pollux on the left is the brighter twin.

Try to spot the Pleiades, a small fuzzy group of stars. Follow the direction of Orion's belt 4 fists to the right, passing the bright star Aldebaran on the way. The five main stars form the unmistakable shape of a tennis racquet.

The Plough is low down in the northern sky  but London's light pollution prevents us seeing clearly its pointers to the Pole Star.

In the west the planet Jupiter is still prominent in the early evening but in a week or two it will be setting too early to see. The 'red' planet Mars rises in the east as Jupiter sets and will be visible all night. Look for it 2 fists to the left or east of Pollux. It's yellowish rather than red, but a lot redder than the star Sirius. Venus and Saturn are not visible at present.

The moon will look full as it rises on the evenings of 29 and 30 January. Today there is a lovely 2-day-old new moon not far from Jupiter. The next new moon starts on 14 February; see its slender crescent in the west 2 days later, soon after sunset.

Roy Singham, 17 January 2010