Station Info :: Space
Solar System ::Planets
A planet is a body that directly
orbits a star, is large enough to be round because of self
gravity, and is not so large that it triggers nuclear fusion
in its interior. All the planets revolve around the sun. There
are nine planets altogether- Mercury, Venus,
Earth, Mars, Jupiter,
Saturn, Uranus, Neptune
and Pluto. Among these nine planets Mercury,
Venus, Earth and Mars are called "rocky" or "terrestial"
planets and the planets like Jupiter, Saturn, Uranus and Neptune
are called the "gaseous" planets. A popular mnemonic
used to remember the planets in order is: My
Very Educated Mother
Just Showed Us
It is not known with certainty
how planets are formed. The prevailing theory is that, when
a protostar forms from a condensing nebula, the remnant of
the nebula becomes a thin disc of gas and dust that revolves
around the protostar.
Localised mass concentrations within this disc form increasingly
dense pockets of matter, which then collapse inward under
gravity to form planets. When the star's core ignites its
solar wind blows away the remaining material, leaving a solar
system like our own.
This theory is being greatly
challenged with the discovery of extrasolar systems that vary
greatly from our own.
View the details of
the following planets