The Moon Guide
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U. S. N. O.
The phase of the Moon right now

Jupiter Watch 2010
10–18 November

Jupiter, Credit Brian Ritchie
Jupiter in 2010. Photo by Brian Ritchie
Where to look and what you can see Anyone who has been looking at the sky this autumn will have spotted Jupiter – it’s the brilliant object above the rooftops in the southeast or south, depending on the time of night you look. Jupiter is by far the largest planet in the Solar System, and even though it’s about 660 million kilometres away from us at the moment, even a small telescope will show you some details on the planet.

The picture at left, by SPA member Brian Ritchie, shows some of the major features. There's one broad dark belt crossing the planet, and several smaller and fainter ones. Usually Jupiter has two equatorial belts, one in the north and one in the south, but for the past year or so the South Equatorial Belt has been invisible for reasons that are not entirely clear. The lighter regions are known as zones.

In the lower half of the picture is a red oval – the famous Great Red Spot. This is not always on show. Because Jupiter rotates quite rapidly, it is only obvious for about three hours in every ten hour rotation period (it needs to be near the centre of the disc to be easy to see). Here are the times during the evening (in GMT) when the Red Spot will be on the centre of the disc during the Moonwatch period:

12 November 17.30
13 November 23.15
14 November 19.10
16 November 20.45
17 November 16.40
18 November 22.25

Sometimes there are other spots on Jupiter – black ones. These are usually the shadows of its four large satellites, Io, Europa, Ganymede and Callisto. You can’t always see shadows on Jupiter – they occur only at six-year intervals, when the Sun is at the right angle, so make the most of them now. Here are the approximate times in the evening during the Moonwatch period when you should see a shadow on the disc, the times being in GMT and for the shadow to be central on the planet.

10 November 21.25 Shadow of Europa
11 November 17.40 Shadow of Io
18 November 19.35 Shadow of Io

Jupiter and its satellites with a small telescope
Although you’ll need a telescope to see the shadows of Jupiter’s moons on the planet, you can see the moons even with binoculars. particularly those that magnify 10 times or more. Take a look and see if you can pick them out, on either side of the planet. Look the next night and you’ll see that they are in different positions. It was seeing this distance dance of the moons that made Galileo realise, 400 years ago when he was the first to spot these moons, that this Solar System in miniature proved that not everything revolves round the Earth, as most people thought in those days. Saying otherwise got him into trouble with the Pope, but fortunately this won’t happen to you now.

The four major satellites, in order outwards from the planet, are Io, Europa, Ganymede and Callisto. A useful way to remember this is the unlikely phrase ‘I Eat Green Cheese’, which gives you their initial letters. You can have some fun trying to devise your own alternative!


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Mare Crisium
Mare Crisium

MoonWatch evenings

10–11 November 2010

12 November 2010

13 November 2010

14 November 2010

15 November 2010

16 November 2010

17 November 2010

18 November 2010

Jupiter Watch 2010
spacer Maintained by SPA Webmaster: Last modified 19 October 2010
International Year of Astronomy Society for Popular Astronomy Society for Popular Astronomy