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Tue, 24 Apr 2012

Planets and a comet

You must have noticed the bright star in the evening sky right now – but what is it? The answer is that it isn't a star but the planet Venus. But as well as this, Mars is also putting on a great show, later in the evening. It is closer right now than it will be for more than two years, so amateur astronomers are making the most of the opportunity. And everyone's favourite, Saturn, is also in the evening sky.

Venus is the closest planet to us and is getting closer all the time. Imagine it travelling in its orbit around the Sun, as shown in the artwork, moving in an orbit which is inside Earth’s orbit. As it moves, the Sun shines on it from different angles, and if you look at it through a telescope you can see that at the moment it looks like a tiny half moon. Throughout April and May it gets closer and becomes a thin crescent. Then on 6 June it actually crosses the face of the Sun – the last time we’ll see this until 2117 – but that’s another story.

Mars is over on the other side of the sky, and is at its highest around midnight. You can spot it in mid sky as a noticeably pinkish bright star, not twinkling like true stars. It was closest to Earth on 6 March, when it was 63 million miles away.

Saturn rises later on, and is visible in the late evening over to the east, near the star Spica in Virgo. It was at its closest to Earth for this year on 15 April.

To see a popular guide to the sky this month, go to our Young Stargazers Sky Guide.

Top: Finder chart for Comet Garradd. Click to enlarge. Above: Photo of the comet (the blue blob) on 23 March. The field of view is 5º l-r.

The comet visible is Comet Garradd. It is quite faint, at around 9th magnitude, and hard to see unless you have fairly good conditions but it is fairly easy to photograph. At right is a finder chart, so try your luck, but be warned that it is quite small and requires a magnification of at least 20 to show it well. The comet is currently in Ursa Major, which is virtually overhead at the moment, and the two stars at left of the finder chart are the 'Pointers' in the Plough or Ursa Major. Click here for the latest observations.


Added by: Robin Scagell