IF THE sky is clear on the evening of Tuesday, February 23, look to the east at around half past six...and wait. After a short while you'll notice the sky in that direction brightening, and soon after you'll see a big, almost-Full Moon rising up from behind the horizon like a silver-white balloon. And as it climbs higher you'll see it is being trailed by something - a very bright, blue-white star, shining to its lower left. Look carefully and you'll see that unlike the other bright stars shining in the sky, the one following the Moon isn't flashing or twinkling. That's because it is actually a planet, the planet Jupiter.

Jupiter is the largest world in the solar system, and absolutely dwarfs our own. An enormous, bloated ball of gases and liquid, it is so huge a dozen Earth's could fit across its equator in a line and if it was hollow it could contain a thousand Earths.

If you have a pair of binoculars handy, focus them on Jupiter soon after it has risen and you'll see three tiny stars hugging close to it, arranged in an almost diagonal line, angling down from lower left to upper right, two beneath and a third one above the planet itself. These are three of Jupiter's family of 63 (yes, 63!) moons. If you look again at 10pm you'll see the view has changed: a fourth moon will have joined the party, to the lower left, having emerged from behind the planet since you last looked.

This is why astronomers love looking at Jupiter. Every night the arrangement of moons changes, as they pass behind and in front of the planet from our viewpoint here on Earth. If you want to know which one is which, there are lots of websites and free phone apps which name them for you.

Stuart Atkinson

Eddington Astronomical Society of Kendal