THE PLANETS OF THE SOLAR SYSTEM

Planet	Average distance from Sun (in millions of miles)	Time taken to orbit the Sun (in Earth days)	Period of rotation (in Earth days)	Diameter at Planet’s Equator
Mercury				58.63	3033 miles
Venus			224.7		7521 miles
Earth			365.2		7926 miles
Mars				1.02	4222 miles
Jupiter				0.41	88,846 miles
Saturn			10,747	0.44	74,897 miles
Uranus			30,589	0.72	31,763 miles
Neptune			59,800	0.67	30,775 miles
Pluto			90,588	6.39	1485 miles

The sun, the star closest to Earth, anchors our solar system. Compared with other stars, it is only average in size. For example, Alpha Orionis in the constellation Orion, commonly known as Betelgeuse, is almost 400 times bigger than and 10,000 times brighter than-the sun. Still, if the sun were hollow, a hundred Earths could fit inside.

Like all stars, the sun is a ball of hydrogen gas that radiates heat and light. It generates power by nuclear fusion: Atoms are rammed together, producing nuclear energy. Every second, the sun converts some four million tons of matter into energy.

Earth orbits the sun at a distance ideal for terrestrial life, provided that Earth’s atmosphere protects us from the sun's heat and deadly radiation. The sun is a third-generation star, composed of recycled elements from two previous stars. It is about 74 percent hydrogen and 25 percent helium, with traces of iron, carbon, calcium, and sodium. These same elements are found in planet Earth and our bodies.

Date: 2015-04-20; view: 1295