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.
Epsilon Aurigae is close to one billion miles in
diameter and VV Cephei has a diameter of two
billion miles, known as the super-supergiants.
There are also stars that are small. One of the
smallest is the Whale and it has a diameter of
1,600 kilometres. Small stars are known as white
dwarfs. Stars also have different temperatures.
Temperatures ranging from 2,100C to 50,000C.
The temperature of the stars is indicated by the
colour of the stars. The blue colour stars are the
hottest and usually the brightest stars, the yellow
stars are medium hot, and the red stars are coolest
and the most dim. Over time, there have been
many questions concerning the supply of gas
clouds in our galaxy. Some people concluded that
there will be only enough to fuel the creation of
stars for another 200 million years. Due to this
immature hypothesis, astronomers investigated and
came to the conclusion that there will be materials
enough for the creation of new stars for at least
another 10 billion years. Other questions asked
were: will there be new stars being born after 10
billion years and how long will the stars last? The
question concerning new stars being born after 10
billion years is still left unanswered. Certain stars
will last for a very long time because "stars with
masses from one-quarter to one-tenth that of the
sun burn long and slow, some lasting more than 10
trillion years before finally sputtering out"[2]
(Adams and Laughlin). Nothing in the universe
seems to last forever. From studies, astronomers
predict that "by 10 trillion years from now, the last
stars will have winked out. The sky, containing the
darkened and collapsed corpses of a trillion trillion
once brilliant suns, will finally fade to black"[3]
(Adams and Laughlin). Stars seem enduring, but
eventually die out. Stars die out when they have
used up all their hydrogen fuel. The hottest stars
actually have the shortest lifetimes, usually
100,000 years. The life expectancy of our sun is
about 12 billion years. It has already lived half of
its lifetime, and in about 6 billion years the sun will
begin to "die." By that time, the sun will have used
up most of its energy fuel and will start releasing its
gases into space. Some stars die quietly and some
stars explode. Before dying out, stars go through
processes of expansion and contraction. When a
star has used up all its hydrogen supply, the helium
in the core begins to fuse into carbon which causes
the star to expand and become a red giant for
many thousands of years. After thousands of
years, the star will collapse and shrink to the size
of a white dwarf star. This entire process of
expansion and contraction will take about
100,000 years. When our sun expands and
becomes a red giant, "its hot surface gases will
swallow up Mercury, the planet closest to the Sun,
and vaporize the planet_Our planet\'s climate will
have grown warmer_The oceans will heat up_until
life on Earth surface will be impossible. Earth will
become a molten dead planet"[4] (Gallant 63).
Centuries later, the sun will collapse. It will shrink
and the Earth will begin to cool. There will be
oceans again because: the huge