Jupiter is the fifth planet from the Sun, located
in between Mars and Saturn. Jupiter is the first gas planet in our
solar system, as well as being the first of what are called the Outer
Planets. Jupiter is much further away from the Sun than Earth. It's
average distance from the Sun is almost 470 million miles. Its orbit,
or path it follows, around the sun is nearly a perfect circle. The
closest it comes to the sun is about 460 million miles, and the
furthest away it gets is a little over 500 million miles.
Since Jupiter is so much further away from the Sun than Earth, its
year, which is the time it takes to go around the sun once, is very
long. A year on Jupiter is almost twelve Earth years! A day on
Jupiter, which is the amount of time it takes to spin around once, is
much shorter than a day here on Earth. The giant planet's day is only
about ten hours long, less than half as long as a Earth day.
- Can I See It?
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Yes you can, and you don't need a telescope to see the ruler of the
night sky. When Jupiter is visible, it is usually the brightest light
in the night sky. The only objects that are brighter are the Moon and
Venus. There are times when you can see Jupiter in both the early
morning and evening.
Jupiter and its moons are so large that you can see the basic color of
the giant planet with just a pair of binoculars. If you have patience,
you can usually pick out one or more of the largest moons of Jupiter
with your binoculars! The way to see the moons with binoculars is to
steady them against something solid and look at the planet. After your
eyes have had a minute or two to adjust to the light, you will see one
or more small points of light. These lights will be a different color
than the stars. Congratulations, you have found Jupiter's moons!
- How Big Is It?
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Jupiter is so large that it is hard for us to grasp just how big it
is. Jupiter is over 85 thousand miles in diameter, dwarfing Earth,
which is a little over 7,600 miles in diameter. Jupiter is so large
that 1300 Earths could fit inside it! Put another way, if you had a
ball that was about the size of a dime, Jupiter would be the size of a
basketball!
- How Many Moons Does It Have?
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Jupiter is like a miniature solar system. The giant planet has at
least sixteen moons, and possibly more. The four largest moons of the
planet, called the Galilean moons, are in the picture at the right.
The two largest moons are both bigger than the planets Pluto and
Mercury, and the largest of them is almost the size of Mars!
In addition to being very large, these four moons of Jupiter are
also very interesting. Europa, the top moon, is a giant ball of ice.
Io, the second moon in the picture, has active volcanoes! Io is the
only place in the solar system besides Earth where we have found
volcanoes. Callisto, the third moon in the picture, is covered with
thousands of craters, which are the result of collisions with other
objects in space. Ganymede, the largest moon, is made up of rocky ice.
- How Did It Get Its Name?
- The Romans named Jupiter after the supreme god in their religion.
This is easy to understand, since it is the largest planet in the sky.
Many of the planet's moons have been named for Jupiter's daughters.
- What Is It Made Of?
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As large as Jupiter is, it is not a rocky planet like Earth or Mars.
Jupiter is a gas planet, which means that is not solid at all, but
instead is a giant cloud made up mostly of the gas elements hydrogen
and helium. You may be wondering "If Jupiter is just gas, how can
it be so large and what holds it together?". These are both
excellent questions.
Most things in the universe are not solid, but are giant balls or
clouds of gas, and Jupiter is the same. Our Sun is a ball of gas that
also gives us heat and light. What holds Jupiter together is the same
thing that makes something drop to the ground here on Earth. That
force is called gravity.
Billions of years ago, Jupiter started forming when several clouds
of gas began to accumulate in the same place. In much the same way
that you build a ball of snow for a snowman, more and more clouds
joined the crowd until the planet began to take shape. As the original
ball of gas became bigger, it attracted, or gathered in, other clouds
of gas. The larger the ball got, the planet's gravity, or force that
attracted the other clouds, also grew. This continued until Jupiter
grew to its present size.
- What's It Like on the Surface?
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Since Jupiter is a gas planet, it doesn't have a surface. This means
that if you tried to land on the planet, you would not be able to find
anything solid to land on. This does not mean that Jupiter does not
have its own strange kind of "weather".
The clouds that make up Jupiter are constantly swirling around the
planet, driven by winds that average over two hundred miles per hour.
The winds create an ever-changing pattern of what we call storms on
Earth. The most famous of these storms is the Great Red spot, which
you can pick out in the picture of Jupiter and its moons at the top of
the page
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