Planets are bodies in the Solar system that revolve around the sun the way the earth does.
Planets have been in existence as their stars. There are nine planets, viz. Earth, Jupiter, Mars, Mercury, Neptune, Saturn, Pluto, Uranus and Venus. They are from the left over clouds comprising dust and gas. They are globe shaped, however, 20 per cent less than the size of their respective stars. Though there are nine planets (including Pluto, which is not a planet), the scientists believe there are more giant planets yet to be discovered!
Such extra-solar planets are very far away from the sun. Yet by the wobbling of their stars, their presence is reckoned. Thus, the study of space goes deep like a bottomless pit. These nine planets had been spotted during the ancient times itself. Few planets with rocky surface are called Terrestrial planets. The remaining ones having gaseous or liquid surface are known as Gas planets. There are nine stars known to have planets. Some of them are 70 Virginis, 47 Ursae Majoris and 51 Pegasi.
Space probe is defined as Automatic Computer controlled (manned or unmanned) spacecraft fired into space to explore the planets. It was in 1962 that the first planetary probe, named as Mariner 2, by the USA, flew over the Venus. Most of the space probes are named as ‘Fly-bys,’ because they simply fly past their target without making an attempt to land on there. But before that, Soviet Union’s Sputnik – 7, was launched into space in 1957.
For the first time, Soviet Union had sent a dog called “Laika” on board Sputnik-2 in 1957. And the first manned space craft, Vostak- 7, was again sent by Soviet Russia in 1961 with a man by name, Yuri Gagarin.
At times, in order to save fuel consumption, the particular space probes gain momentum to farthest planets by using the nearby planets’ gravity. It is called as “Slingshot.”
Cosmonaut and Astronaut are the same. The former is Russian and the latter is the American.