(ESTD. BY GOVERNMENT OF TAMILNADU)


Venus


After the Moon, the second brightest object in the night sky is Venus. People often mistake Venus for a bright star. It is 10 times brighter than the brightest star Sirius. In olden days it was known as the Morning star and the Evening Star. The brighteness is due to the highly reflective nature of the Sulphuric acid clouds high in the planets atmosphere.

It is only slightly smaller than the Earth so it is known as Earth’s sister planet.

It’s orbit also lies within Earth’s. So Venus, like Mercury, is found close to the Sun in the Sky. It can never be seen more than 47 degrees away from the Sun. Venus also exhibits phases like the Moon.

Venus is a dark, hostile world of volcanos and suffocating atmosphere. The atmosphere is mainly made up of Carbon dioxide and little Nitrogen and sulphuric acid. Most of the sunlight is reflected back high in the atmosphere and only a quarter of Sunlight falling on Venus reaches the surface and warms the ground and atmosphere. Like the glass trapping heat in a green house, the atmosphere containing carbon dioxide traps the heat. So the temperature on Venus builds up and is always very hot even during night time. The average temperature on its surface is 465 degrees making it the hottest planet.

The thickness of the atmosphere is 90 times greater than Earth’s and the atmosphere and the thick clouds prevent our view of its surface. Only radar studies and space probes can provide information on the surface of Venus.

In 1970 the Russian probe Venera 7 became the first to land on Venus and send data to Earth. Between 1990 and 1994, the spacecraft Megallen, using RADAR technique produced images of large areas of Venus.

Venus was named after the Roman goddess of beauty. In keeping with this theme, virtually all the features on the planet are given female names.

In the southern part of the planet a high and great plateau over 1500 km wide is given the name ‘Lakshmi Planum’ There are many craters on Venus surface. Most of them were found by vocanic activity.

Venus goes round the Sun in about 225 Earth days. It sluggishly completes one rotation on its axis in 243 days. Peculiarly, the spin of the planet is opposite that of Earth’s rotation. Which means, it rotates from East to West !

The orbits of Mercury and Venus lie inside Earth’s orbit, so they are the only planets which can pass between Earth and Sun.

Sometimes rarely,they can be seen crossing the disk of the Sun. The event is known as transit.

Transits of Venus are much rarer than transits of Mercury. In June 2004 we witnessed a transit Venus. Again in the years 2012 and 2117 transits of Venus will occur.