We are not being favoured with many clear nights just now but I did manage to catch the close approach of the Moon and Saturn back at the beginning of December. Of course the big event during December was the successful launch of the James Webb telescope on Christmas day using the Ariane 5 rocket from French Guiana. I’m not sure that some members of my family appreciated me being glued to the screen during their visit! The launch was part of the European Space Agency’s contribution to the project and perhaps the Ariane 5 rocket doesn’t get the credit it deserves for being such a reliable launch vehicle over many years.
The following chart represents the night sky at 10.00pm GMT on the 8th of January and at 9.00pm GMT on the 23rd January. To use the chart, face south at the appropriate time with the bottom of the chart towards the southern horizon and you will see the stars in the chart. If you are observing a little earlier in the evening then the view is shifted 15 degrees eastwards for every hour before the specified time.
Last month was mostly about the bright stars which form the Winter Hexagon and the Winter Triangle so this month will be a bit more about constellations. There is no difficulty with navigation because Orion is at its best just now and is the obvious starting point.
To the north east of Orion you can easily locate two prominent stars, Castor and Pollux, the brightest stars in the constellation Gemini- The Twins. It is probably well known because it is one of the zodiacal constellations. The lower star, Pollux, is the brighter of the two stars at magnitude 1.1 and is a single yellow star. On the other hand, Castor is a multiple star system with overall magnitude 1.6 and with the help of a telescope can be resolved into two white stars with a red companion and each of these stars is a double giving a total of six stars in the system! Castor and Pollux represent the heads of the twins while several stars of magnitude3/4 represent their bodies with the magnitude 1.9 star, Alhena, being the foot of Pollux paddling in the Milky Way. You should find it easily on a line between Betelgeuse and Pollux.
To the east of Orion and directly below Pollux you will find the bright star, Procyon, part of the Winter Triangle which we described last month, in the constellation Canis Minor- The Lesser Dog. This constellation is meant to represent one of Orion’s hunting dogs but has little to offer apart from the white star Procyon the 6th brightest star visible from the northern hemisphere at magnitude 0.4.
To the south of a line joining Procyon and Betelgeuse and in line with Orion’s Belt lies the brightest star in the entire sky, Sirius, in the constellation Canis Major- The Greater Dog, said to represent Orion’s other hunting dog. Sirius, also known as the ‘Dog Star’, shines at a brilliant magnitude -1.4 and is only 8.6 light years distant. There is considerably more to this constellation but being close to the horizon does not yield itself to easy observation at our latitude. However your challenge this month is to attempt to see the open star cluster M41 which is shown on the chart with a red cross just below Sirius. It should be visible to the naked eye as a hazy patch the size of the full moon. You will need clear skies and be free from light pollution.
To the west of Sirius and just below Orion is the constellation Lepus- The Hare. I can’t say I am familiar with this constellation because it is surrounded by other bright stars but its central stars are brighter than magnitude 3 and the distinctive shape should make it easy to pick out albeit close to the horizon.
Finally the constellation, Monoceros- The Unicorn, lies mostly within the Winter Triangle but lacks any bright stars and is outshone by the brightness of its neighbours. Nevertheless knowing its location and distinctive W shape may help you locate it.
Something to look out for
The planets continue to provide a spectacle as long as conditions are good. Venus is moving into inferior conjunction (between the Earth and the Sun) so will disappear from the evening sky but reappear as a morning object next month. Mercury is doing the same but a bit behind and on the 4th January it will form a triangle with Saturn and a very young crescent Moon low in the south west just after sunset (4.15pm). Mercury itself will set at 5.45pm. Even the Moon will present a challenge to the unaided eye as it will be only two days old and close to the horizon just before setting.
Look out for a close approach of the waxing crescent Moon and Jupiter on the 5th and 6th January. There might be a better chance to see Mercury on the 7th January when it is at its greatest eastern elongation (biggest angular separation from the Sun) and sets about ninety minutes after the Sun or on the 12th January when it is at its highest altitude. If you don’t have any success observing Mercury then just enjoy the brilliance of Jupiter. Clear skies.