Download The Planets

Astronomy
The Planets
The Planets
• Mercury, Venus, Earth, Mars, Jupiter,
Saturn, Uranus, Neptune
– Pluto is now considered a dwarf planet
– All revolve around the sun
– All rotate about their axis
• Astronomical Unit (AU)
– Distance between the Sun and the Earth
• Equatorial diameter
– Around its center
The Terrestrial Planets
• The terrestrial planets are the four planets
closest to the sun. (Mercury, Venus, Earth,
Mars)
• Terra
– Latin word for Earth
• Terrestrial planets are:
– small, dense and have rocky surfaces.
• Terrestrial planets have:
– crust, mantle and iron core.
• What do the number of craters on a planet’s
surface tell us?
– How quickly their surface changes
Mercury
1. Closest to the sun
2. Smallest Planet
•
One day on Mercury is 59
days on Earth
•
One year on Mercury is 88
days on Earth
•
400oC during day
•
-150oC at night
Venus
1. Second Planet from the Sun
2. Brightest object in Earth’s night
sky after the moon
• Hottest planet in solar system
due to density and composition
of atmosphere :460oC
• Volcanic Activity
• Small number of impact craters
• Sister planet to Earth (Similar in
size)
Earth
1. Third Planet from the Sun
2. One Moon
3. Only planet in solar system
where liquid water exists
• Water is essential for life
• Only planet in the solar
system with life?
Mars
1. Fourth Planet from the Sun. “The Red Planet”
2. Olympus Mons – Largest volcano in the Solar
System
25 km high (3 times the height of Mt.
Everest)
•
Mars has seasons like Earth
•
Named for the Greek god of
war
• 2 moons, Phobos and Deimos
• Evidence of having liquid water at one time
Comparison of Inner Planets
The Outer Planets
• The outer planets are the four planets furthest
from the sun. (Jupiter, Saturn, Uranus,
Neptune)
• Outer planets are called the Gas Giants
• The outer planets consist mainly of liquid
hydrogen and helium and may have a small
cores of metal and rock
• Outer planets are much larger than the
terrestrial planets
• Cooler than inner planets
• Outer planets have more moons than inner
planets
Jupiter
1. Largest planet in the solar system
• Composed mostly of gasses
2. 1 day on Jupiter is less than 10
hours on Earth
• Storms exist on Jupiter, last for
100’s of years
• The great red spot was first
observed in 1664
• Jupiter has over 60 moons
• Europa is completely covered by a
salt water ocean covered by ice
• Scientists think life may be
possible in this ocean
Saturn
1. Best known for its rings composed of ice and rock
• Over 60 moons
• Titan has a thick atmosphere and may have rivers and
lakes of ethane
Uranus and Neptune
• Planets are similar in size and color
• Uranus is unusual in that it rotates sideways compared to the other
planets
• Uranus has 27 known moons
• Neptune has 13 known moons
The Outer Planets
(Number of Moons outdated…)
Dwarf Planets
•Only 5 known Dwarf Planets in the Solar System – could be 100’s more
• Definition created in 2006
•Pluto resides in the Kuiper Belt beyond Neptune’s orbit.
• Has a moon, Charon that is about half its size
• Ceres is the only known dwarf planet that orbits in the asteroid belt
between Mars and Jupiter
Pluto
Ceres
Dwarf Planets
What makes a Planet a “Planet”
•
•
How did Pluto get demoted?
A planet according to the International
Astronomical Union must:
1. Orbit the sun
2. Not be a satellite
3. Be massive enough for its own gravity to
keep it round
4. Be big enough to dominate its orbit
– Scientist’s believe that Pluto fails this last test