Jupiter, under the influence of the Sun, puts on a glowing performance

New year revellers might have been forgiven for believing that aliens had arrived when a bright light appeared in the southern sky. In fact it was the planet Jupiter, which outshone everything but the Moon.

New year revellers might have been forgiven for believing that aliens had arrived when a bright light appeared in the southern sky. In fact it was the planet Jupiter, which outshone everything but the Moon.

As well as being strongly illuminated by the Sun, which lies well below the horizon, Jupiter approached its closest point to Earth – a mere 395 million miles – making it glow like a child's nightlight in the sky.

A full moon – and more than the usual number of people under the influence of a few drinks – created the perfect conditions for reports of unidentified flying objects.

Unlike stars, which appear to twinkle due to atmospheric interference with starlight, Jupiter's glow was more constant, much like that of the Moon itself.

The giant planet, which is the biggest in the solar system, appeared to hang among the stars of the constellation Gemini, near the bright "twins" Castor and Pollux in the south-eastern part of the sky.

Amateur astronomers with binoculars were able to see the four largest of Jupiter's 28 satellites, the moons Io, Ganymede, Europa and Callisto. Galileo was the first person to observe them, through his hand-built telescope in 1610.

Those with more modern instruments might have spotteddetails of Jupiter's cloudy atmosphere, including the permanent storm, known as the Great Red Spot, which swirls around the planet.

Jupiter is normally the fourth brightest object in the sky, after the Sun, the Moon and Venus. Sometimes it is even outshone by Mars when the two planets are, respectively, furthest and closest to Earth in their orbits around the Sun.

Jupiter is mostly composed of dense gases which get thicker towards the planet's centre. However, scientists believe that it may also possess a rocky core about 10 or 15 times the mass of the Earth. The planet radiates slightly more energy than it receives from the Sun, which is thought to result from heat generated by gravitational compression within its solid core.

One of the most surprising discoveries about Jupiter was made following a visit by the space probe Voyager 1 in 1970, which found planetary rings similar to the famous rings of Saturn, but much fainter.

Like those on Saturn, the rings of Jupiter are composed of fine grains of rock that have been spun off into space.

* The National Space Science Centre in Leicester will become Britain's leading facility for providing information about the dangers of an asteroid collision with Earth, the Science minister, Lord Sainsbury of Turville, said yesterday. The centre was chosen out of a shortlist of three institutes vying to handle data on asteroid threats.