Mars
Essay by review • November 7, 2010 • Essay • 386 Words (2 Pages) • 1,137 Views
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.
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