2. A planet is any body in orbit around the Sun that has
enough gravity to form a sphere and that has cleared
the neighborhood near its orbit of smaller objects.
The inner planets
are mostly rock and
metal.
8
5
1. Mercury
2. Venus
3. Earth
4. Mars
3
1
7
4
The Sun
The outer planets
are mostly gas and
dust.
2
6
5.
6.
7.
8.
Jupiter
Saturn
Uranus
Neptune

3. The planets that are made of gas and
dust are much bigger than the planets
that are made of rock and metal.
Jupiter
Uranus
Earth

4. Which of the following planets is mostly rock and metal?
Saturn
Uranus
Mars

5. Saturn is made of gas and dust. Do you think it
would be bigger or smaller than Mars?
Bigger than Mars
Smaller than Mars

6. Match each planet name to the diagram.
Saturn
Neptune
Mercury
Earth
8
5
3
1
7
4
2
6
Venus
Jupiter
Mars
Uranus

7. What is Neptune mostly made out of?
Metal and Rock
Dust and Gas

8. Astronomers are planning to define
a new type of planet.
This new type is a “plutoid” or “dwarf
planet.”
 Plutoids are not big enough to clear their
path of other objects.
 Pluto is a plutoid. So are Ceres, Eris,
Makemake, and Haumea.


9. Pluto is in orbit around the sun, but it has a smaller
object in its immediate neighborhood.
Is it a planet?
Yes
No
Yes, but it’s a
dwarf planet