OUR BEAUTIFUL UNIVERSE: Jupiter without its Southern Equatorial Belt
In the autumn of 2010, the gas giant planet Jupiter is well placed for observation from the Earth. On September 21, the planet is at its closest to the Earth for more than 4 decades, so appears somewhat larger and brighter than usual. This date is the Jovian opposition, when the planet is opposite the Sun in the sky and visible throughout the night.
Jupiter has a diameter of 143000 km across its equator, but only 134000 km from pole to pole. This squashed shape results from its rapid rotation. Despite being big enough to hold more than 1300 Earths inside it, the planet rotates in less than 10 hours, making it bulge out at lower latitudes.
This year saw a major change on Jupiter when the South Equatorial Belt disappeared in May. This large weather feature vanishes every few years and typically reappears 1 to 3 years later, so it may return again at any time.
Advances in imaging technology and techniques mean that amateur astronomers are now able to produce images as good or better than those produced by professional telescopes just three decades ago. In this image, obtained in the UK by amateur astronomer Pete Lawrence, the Jovian weather systems are clearly visible. The broad brown stripe running diagonally from left to right is the North Equatorial Belt.
The disc just off the bottom right is Ganymede, Jupiter's largest moon, here recorded as it passed in front of the planet. Ganymede is one of the four moons identfied by Galileo between 1609 and 1610, one of the discoveries commemorated in the International Year of Astronomy 2009.