Venus – Planet Profile
by Kevin Brown : last updated: January 13, 2009Welcome back!
Venus from Pioneer (credit NASA)
Venus is the second closest planet to the Sun. It is 67 million miles from the Sun.
Venus’ orbit is almost circular as the eccentricity of the ellipse is very small. Each orbit takes 225 Earth days.
Venus rotates on its axis only slowly, taking 243 Earth days. So strangely, a Venus day is longer than a Venus year.
Like Mercury, the other planet that is closer to the Sun than Earth, Venus is hot and inhospitable. Although in other respects, Venus is quite different.
Venus is covered by a dense, swirling, opaque atmosphere of Carbon Dioxide. This produces a major “greenhouse effect” and makes Venus very hot.
Venus is hotter than Mercury, with a surface temperature of about 500C, even though it is twice as far from than the Sun.
Sometimes Venus is referred to as Earth’s sister planet, because they are of very similar size. But as we have just seen, surface conditions are very different.
Because its orbit is closer to the Sun the Earth’s, Venus always appears in the same area of the sky as the Sun, but unlike Mercury it is much easier to observe.
Indeed, Venus is often a brilliant object in the sky, partly because its dense atmosphere reflects to much light.
Through a telescope though, it is rather disappointing. The cloudy atmosphere prevents us seeing any surface features.
Venus does exhibit phases though. Because of its position relative to the Earth and Sun, its face is sometimes fully illuminated, sometimes only partly.
The phases were first observed by Galileo in 1610. Venus is new when closest to us. It is full, when furthest away.
Transits of Venus, when the planet passes across the face of the Sun from our viewpoint here on Earth, are very interesting to watch.
Transits occur in pairs separated by eight years, about every 120 years.
The last transit of Venus was in 2004. I personally, got a splendid view of it by projecting the Sun’s image onto a sheet of paper.
There will be another transit in 2012.
There have been several space missions to Venus. Some have moved down through the cloud layers and tried to investigate the surface.
Most of our knowledge of the planet’s surface has come from radar mapping by the Magellan probe in the early 1990’s.
This surface mapping revealed a fascinating volcanic world with many craters. There is a huge plain and two main areas of highlands called Ishtar Terra in the north and Aprodite Terra around the equator.
There are also mountains – one is higher than Everest here on Earth.
STill confused. Southern Minnesota.
Where and when would I look to see Venus. I was confused and thought that the bright spot to the east and southern sky was our bright Venus but now understand that it is indeed Jupitor. Help me so that I don’t tell anyone else incorrectly. Have Mercury and Saturn also moved away from our view right after sunset?
Sincerely,
Rich
Hi Rich, Thanks for getting in touch.
Yes, the very bright object in the South East evening sky is Jupiter, not Venus. At present, Venus is best seen in the morning sky, low in the East before sunrise.
Mercury is difficult, but you may see it low in the West at dusk. Saturn is now lost in the sunset twilight.
You may like to bookmark the SPA Sky Diary as it’s very useful and updated quarterly.
Hope that helps,
Kevin