Another type of planets are Dwarf planets. The current number of dwarf planets (according to the IAU on the 1 st of April, 2007) is only three. The asteroid Ceres is the only asteroid known to be round. Pluto is also considered a dwarf planet. And Eris, a little larger than Pluto, is also a dwarf planet.
Earth is the only known habitable planet in the universe. It is about 12,700 km in diameter it’s mass, 6,000,000,000,000,000,000,000,000 kilograms about 4.55 billion years old. Earth’s moon is the third largest in the Solar System, after Ganymede and Titan.
Venus is the brightest object in the sky (excluding the moon). It has clouds of sulfuric acid in it’s atmosphere, reflecting most of the sun’s light and obscuring the view of the actual planet. Venus is one of four rocky planets in the Solar System. Venus’s atmosphere is full of carbon dioxide and sulfur dioxide which generates an extremely strong greenhouse effect. This in turn raises the surface temperature of Venus to over 460 ° c.
Jupiter is the biggest planet in the Solar System. It’s mass is approximately 317 times the mass of Earth, yet it is 1,317 times the volume of Earth. Jupiter's atmosphere is made of about 90% hydrogen and 10% helium by volume. Jupiter has the most moons of any planet in the Solar System-63 to be exact. The four main moons are Io, Europa, Ganymede and Callisto.