Ast1141Lec20GiantPlanets.pptx - The Giant Planets Astronomy...

The Giant Planets
Astronomy 1141

Life In the (Outer) Solar System
•
We’ve looked at the inner solar system
•
Mars is a place to look for signs of life
•
What about the outer solar system?
•
The giant planets themselves are very unlikely
sites for life
•
But they host numerous moons, some of which
rival the terrestrial planets in size!
•
It is much colder in the outer solar system,
which means that solar heating is not going to
be efficient
•
You will need another energy source…

Composition of the
Sun and Terrestrial
Planets:
Very Different
=> Formed In
Different Ways
Earth:
“Rocks”
And
“Metals”
Trace H, He
~30% CNO
~70%
“Others”
Sun: H (71%), He (27%), and
a bit of everything else:
1.5% CNO, 0.5% “others”
WHAT ABOUT
THE GIANT
PLANETS?

J+S ~100-300x Earth
U+N ~15-20 x Earth

Gas Giants:
Jupiter & Saturn
5 & 10 AU from the Sun
Ice Giants:
Uranus & Neptune
20 & 30 AU from the Sun
Neptune
Uranus
Saturn
Jupiter
The outer planets of the solar system are the
gas giants & ice giants .
What is the difference
between gas & ice?

Gas Giants
Ice Giants
The giant planets are massive enough to retain heavy
hydrogen- and helium-rich atmospheres.

Density: Key Composition Clue
The densities of
the giant planets
are between the
Sun and Earth
But…these don’t
account for
gravitational
compression!