Mars

Mars

On a clear night, only a few hundred stars can be

seen without the use of any astronomical

instruments. The Milky Way Galaxy consists of at

least 200 billion stars. Stars are huge balls of hot

gases. The sun is a star, but it is not the largest

star; it is only the nearest star. A star has three

recognizable stages: its birth; the years in which it

exists; and its death. Its formation and its life

expectancy have captured the curiosity of

astronomers for centuries. Astronomers from the

past have devoted their entire lives to the studying

of the formation of stars. Gases make up 99

percent of the materials in the galaxy. These gases

in space gather together to form clouds of gas,

known as nebulae. Millions of years later, "the

temperature of the cloud climbs until it becomes

hot enough to radiate light. It is then no longer a

gas cloud; it is a star"[1] (Asimov 182). New stars

are formed when nuclear reactions occur in these

concentrated clouds of gas. Stars are made of 60

different elements, all of which are found on Earth.

Elements such as hydrogen, helium, iron, and

calcium. The average star's atmosphere consists of

87% hydrogen, 10% helium, and 3% of other

elements. Each star has its own motion, but it is

not obvious. Although the sun appears to be huge,

many stars are bigger than it. Our sun's diameter is

864,000 miles. Betelgeuse, a red supergiant, has a

diameter 500 times bigger than the sun: 500 million

miles. Betelgeuse, though, is not the biggest star.