Space and Time
Size: Diameter 12,104km
Mass: 4.865x10(exp24)kg
Composition: Iron/nickel core
Mean temperature: 480°c
Distance from Sun: 108.21 million km
Atmosphere/weather: Ninety times Earth pressure, mainly carbon dioxide
Moon/satellites: None
Orbital length: 225 days
Length of day: 243 Earth days
Distance from Earth: Max 258 million km, min 42 million km
On the morning of 8 June 2004, the planet Venus crossed between the Sun and the Earth. During this Transit of Venus, the planet was seen to move across the bright face of the Sun. These transits are amongst the rarest of planetary alignments. Only six such events have happened since the telescope was invented - in 1631, 1639, 1761, 1769, 1874 and 1882. No one alive that day had had the chance to observe such an event before. The next transit will occur on 6 June 2012.
'The Founder of English Astronomy', 1891, by Eyre Crowe (1824 - 1910)
A transit of Venus was first observed by Liverpool-born astronomer Jeremiah Horrocks in 1639. He used a telescope fixed to a wooden beam which projected an image of the Sun onto a piece of paper. This allowed him to see Venus cross the face of the Sun. A painting of the event, from Walker Art Gallery's collection, gives an artist's impression of Horrocks making that historic observation. Because of his achievement, he is known as the father of British astrophysics.
You can find out more about this year's transit and Jeremiah Horrocks at www.transitofvenus.org.uk [opens new window].
The planet Venus appears at first to be quite similar to our Earth. It is a similar size, mass, composition and distance from the Sun. That, however, is as far as the similarities go. Venus has no oceans and is covered by thick clouds that trap surface heat. This creates a greenhouse-like atmosphere where the temperature, at over 450C, is hot enough to melt lead. Atmospheric pressure is so intense it is equivalent to being 900m deep in Earth's oceans. Space probes sent from Earth that have landed on Venus have only lasted an hour or two before being crushed.
A colour image from the Russian Venera 13 spacecraft. It landed on Venus' surface in 1981 and sent back images like these before being crushed by the intense pressure.
The atmosphere is made up of mostly carbon dioxide. Sulphuric acid falls like rain. There is virtually no water vapour. In the upper layers of the atmosphere the clouds move faster than any hurricane-force winds on Earth.
Venus rotates very slowly. It takes 243 Earth days to complete one revolution, but only 225 days to orbit the Sun. This means a day on Venus is longer than a year! Venus also has a 'retrograde' rotation, meaning it spins in the opposite direction of its orbit around the Sun. On Venus, the Sun rises in the west and sets in the east.
Three large impact craters with diameters ranging from 37km to 65km are visible in the fractured plains. Features typical of meteorite impact craters are also visible. Rough radar-bright ejecta surrounds the perimeter of the craters; terraced inner walls and large central peaks can also be seen.
The surface of Venus is made up of lowland plains, rolling uplands and highlands. There are no impact craters on the surface smaller than 1.5 to 2km across. This is probably because all but the largest meteorites burn up in the dense atmosphere. Although there is no direct evidence of volcanic activity, over 1000 volcanoes or volcanic craters over 20km wide dot the surface. There may be close to a million volcanoes that are over 1km wide.
Venus has no satellites and no intrinsic magnetic field. The solar winds rushing past Venus do, however, create a pseudo-field around the planet. The NASA Magellan spacecraft produced a detailed radar map of the surface of Venus.
You can watch a short movie clip showing Venus unveiled, courtesy of the NASA Magellan Project.
Venus is the Roman goddess of love and beauty. The planet is so named probably because it is the brightest of the planets known to the ancients. With a few exceptions the surface features on Venus are named after female figures, such as Diana, the Roman goddess of the hunt and Sacajawea, a Native American woman who guided the Lewis and Clark exploration of America.
Venus is the brightest object in the sky except for the Sun and the Moon. Like Mercury, it was popularly thought to be two separate bodies, Eosphorus as the morning star and Hesperus as the evening star. However, the Greek astronomers knew it was in fact just one.
A computer generated view of the Eistla region of Venus
Images, information and videos courtesy of NASA.