planets in the solar system

1. The Planets

2. A. What’s in Our Solar System?
• Our solar system consists of a central star
(the Sun), planets, dwarf planets, moons,
asteroids, comets, meteors, interplanetary
gas, dust, and all the “space” in between.
• Except for Earth, the planets of the solar
system are named for Greek and Roman
gods and goddesses.

3. The Relative Size of the Planets in
the Solar System

7. B. Planets are categorized
according to size and composition
– Small, rocky planets are the inner planets
closest to the sun
– gas giants are the outer planets

8. Inner and Outer Planets
• Inner Planets:
– Mercury
– Venus
– Earth
– Mars
• Outer Planets
– Jupiter
– Saturn
– Uranus
– Neptune

9. 1. Characteristics of Inner Planets
• They are made up mostly of rock and metal.
• They are very heavy.
• They move slowly in space.
• They have no rings and few moons (if any).
• They have a diameter of less than 13,000
km.

10. a. Mercury
• Has a revolution period of 88
days.
• Has 1000° temperature
swings from day to night
because there is no
atmosphere to trap heat.
• Is about 1/3 of Earth’s size
• Is about 1/3 Earth’s distance
from the sun (0.39 AU)

11. b. Venus
• Has retrograde rotation – so
the sun rises in the west and
sets in the east!
• Reaches 900F at the surface
due to a strong greenhouse
effect.
• Venus has no moons and
takes 225 days to complete an
orbit.
• Is about the same size as
Earth
• Is about 2/3 Earth’s distance
from the sun (0.72 AU)

12. c. Earth
• Is the only planet known to
support life!
• Has a surface composed of
71% water.
– Water is necessary for life on
Earth.
• Is the basis for the
Astronomical Unit (distance
from sun to Earth = 1 AU)

13. • Mars appears red because of
iron oxide, or rust, in its soil.
• Mars has two moons and
takes about two years to
complete an orbit.
• Is about ½ of Earth’s size
• Is about 1 ½ times as far from
the sun as Earth (1.52 AU)
d. Mars

14. 2. Characteristics of Gas Giants
• They are made up mostly of gases
(primarily hydrogen & helium).
• They are very light for their size.
• They move quickly in space.
• They have rings and many moons.
• They have a diameter of 49,000 km or
greater

15. a. Jupiter
• Is the largest, most
massive planet.
• Takes about 12 years to
orbit the sun.
• Jupiter has 17 known
moons.
• Is about 11 times larger
than Earth.
• Is about 5 times farther
from the sun than Earth
(5.19 AU)

16. b. Saturn • Has many rings made of ice
that extend about 260,000
miles from the surface but
are less than 1 mile thick.
• Has 19 known moons
• Takes about 30 years to orbit
the sun.
• Is almost10 times larger than
Earth
• Is nearly ten times farther
from the sun than
Earth (9.5 AU)

17. c. Uranus
• Has 21 known moons
• Takes 84 years to
complete one orbit.
• Is about 4 times
larger than Earth
• Is about 19 times
farther from the sun
than Earth (19.1 AU)

18. d. Neptune
• Takes 165 years to orbit
the sun
• Has 8 moons
• Is about 3.8 times larger
than Earth
• Is about 30 times farther
from the sun than Earth
(30 AU)