Planets

The marvels of our own solar world are the nine planets orbiting the Sun. The innermost planet, Mercury, is only half the size of our Moon and completes an orbit every 88 days. There are extreme temperature differences between day and night on Mercury, baking at 450 degrees C during the day and freezing at -212 degrees C at night. Venus is similar in size to Earth yet suffers from a runaway greenhouse effect due to a dense carbon dioxide atmosphere trapping heat from the Sun. As a result, it's hot on Venus (460 degrees C). The bright cloud cover makes Venus the brightest object in the sky as seen from Earth after the Sun and Moon. Our Earth is the third planet, the only place in our solar system known to harbour life. Its atmosphere and magnetic field shield the planet's biosphere from the harmful effects of space radiation. At half of the Earth's size, Mars is our nearest neighbour at a distance of just 35 million miles. It has a very thin atmosphere and gravity on Mars is roughly 1/3 of that on Earth. Beyond the four inner planets lie the gas giants. At a distance of half a billion miles from the Sun, Jupiter is 318 times more massive than Earth and features no less than 63 moons. Its huge cloud belts swirl around the visible surface of the atmosphere, generating Earth-sized storms including the Giant Red Spot with wind speeds of more than 400 mph. Stunning Saturn is the jewel of the solar system with 33 moons and spectacular rings, nearly 1 billion miles from the Sun. It is the lightest planet, with a density just one tenth of Earth's. Uranus also features a ring system and circles the Sun at a distance of 1.8 billion miles, taking 84 years to complete one orbit. Its rotational axis is tilted heavily, probably as a result of a catastrophic collision with another planet-sized body. The outermost planets, Neptune and Pluto, only capture a tiny amount of heat and light from the distant Sun. Neptune is 2.8 billion miles from our star, and Pluto has a highly elliptical orbit with a near point slightly nearer than Neptune and a far point of 4.5 billion miles from the Sun. It takes Pluto 248 years to complete one orbit, and it is the smallest planet in our solar system with a diameter of 1,430 miles.   Comet 17P/Holmes This obscure little comet was hardly detectable at magnitude 17 when suddenly in October 2007 it became one of the brightest objects in the sky Venus Other than the Sun and Moon, Venus is the brightest object in the sky. Here is a daytime snapshot taken in September 2007. Saturn This image of Saturn was captured in March 2007 Jupiter, Ganymede and Io First image taken of the gas giant in January 2005 Saturn Image acquired on 6 February 2005 Jupiter and Europa Jupiter's moon Europa can be seen emerging from its transition across the planet Jupiter's Great Red Spot The biggest storm in our Solar System - April 2005 Mars Have a glimpse at our planetary neighbour named after the Roman God of War Comet C/2004 Q2 (Machholz) Whilst not planets, comets are objects of our Solar System, such as C/2004 Q2 (Machholz). Asteroid 11/Parthenope Animation showing asteroid Parthenope's motion - January 2006 Saturn Image acquired on 4 March 2006 Saturn's Moons An exposure with a highly sensitive CCD camera reveals Saturn's Moons Jupiter and Europa Image of Jupiter also showing one of its moons Europa - June 2006 Comet C/2006 M4 (Swan) This comet emerged from behind the Sun in September 2006 and is on its way into outer space, never to return. Image taken in October 2006. Uranus At a distance of nearly 2 billion miles, this gas giant appears tiny as seen from Earth

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