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Note: I'm still bummed
out about Pluto getting "deplaneted."
Our solar system has 8 planets that
orbit a big star called the Sun. (An orbit is the path that a planet
moves through.) All the planets orbit the Sun in elliptical paths. (An
ellipse is just a stretched out circle.)
All the planets take different amounts
of time to get all the way around the Sun. Our Earth takes a year
to make one complete orbit. In fact, that's how we decided how
long a year should be - it's the length of time it takes us to get all
the way around the Sun!
Also, all the planets
spin while they move around the Sun... Just like tops!
There is another mess of stuff that
orbits the Sun... We call it the Asteroid Belt and it is just a bunch of
really big rocks.
Here's a picture of all the orbits:
If you need to remember the
order of the planets, here's a trick: Just look at the first letters of
each planet in order, starting with Mercury and working your way out...
M,
V, E,
M,
J, S,
U,
N and make up
a funny sentence that uses these letters. Here's one:
Mooing
very eagerly,
Mary
juggled slimy
unicorns
nimbly.
(The funny thing is: Mary's NOT a cow.
FYI, cows cannot juggle.)
How do all their sizes
compare? The big yellow circle is the Sun's size and all the others are
arranged from smallest to largest. (Man, look how little the Earth is
compared to the Sun!)
The inner planets,
Mercury, Venus, Earth and Mars are called terrestrial planets. This
means that they have a hard surface (rock) to stand on.
Jupiter, Saturn, Uranus
and Neptune are called the Jovian planets, since they are all a lot like
Jupiter. (Jove was another name for the Roman god, Jupiter). They are
also called gas giants. This is because they are made of gas and
liquid (but not water). There's no hard surface to stand on!
The very sad,
ex-planet, Pluto,
doesn't get to fit into either of these categories. See? I
still can't let him go. He was our only planet named after a
cartoon dog.
To find out a ton of cool
stuff about each thing, just click on its picture below!
There's one thing
that we think is the very coolest (not cold) thing in the entire solar
system... Can you find what it is?
(Here's a question
we've got for you: On which planet is your weight the closest to what it
is on Earth?)
The Sun |
Mercury |
Venus |
Earth
Our Moon |
Mars |
Jupiter |
 Saturn |
Uranus |
Neptune |
Sources:
In Quest of the Universe, 2nd ed. by Karl F. Kuhn
Voyages Through the Universe, 2nd ed. by Fraknoi, Morrison and Wolff
Universe by Kaufmann
The Complete Idiot's Guide to Astronomy by Christopher De Pree and Alan
Axelrod
The Astronomy Cafe by Sten Odenwald
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