Giant Jupiter

Last week we were talking about the smallest planet in our solar system, this week it is the turn of the biggest planet, Jupiter. Tonight (7 April) Jupiter will be at opposition i.e directly opposite the Sun and therefore at its closest point to the Earth. If you could look down on the solar system the Sun, Earth and Jupiter would be in a direct line with the Earth in the middle. At opposition Jupiter will rise in the east at sunset in the constellation of Virgo, it will be at its highest point in the sky around midnight and will set in the west at sunrise. It will be the brightest object in the night sky after the Moon.

Jupiter is the 5th planet out from the Sun and it is huge, you could fit over 1,300 Earths inside Jupiter. But unlike the Earth, Jupiter is nothing more than a huge ball of gases. It has no rocky core so when we talk about seeing details on the surface of Jupiter we are talking about the upper layers of the cloud belts created by the swirling gases as they travel around the planet. The gases form belts of various shades of brown and orange streaking across the planet parallel to the equator. And because the planet spins so fast on its axis (a day lasts 10 hours) it is flattened at the poles and bulges at the equator, looking like a squashed tangerine.

Jupiter has at least 62 moons circling around it. Four of the moons, Io, Europa, Ganymede and Callisto, are large enough to be seen through binoculars, appearing as tiny stars at the planets equator. They orbit very quickly and change their positions night by night. It was by observing these moons that prompted Galileo to state that the Earth was not the centre of the solar system but instead just a planet in orbit around the Sun.

The most mysterious object on Jupiter is of course the Great Red Spot. The GRS is a swirling area of gas located in the Southern belt that has been observed for over 400 years. It is about 3 times bigger than the earth and is thought to be a storm, but why it is red in colour and why it has remained in the same position for all this time is still a mystery.