Download The Gas Giants Astronomy Lesson 13

The Gas Giants
Astronomy
Lesson 13
The four outer planets: Jupiter, Saturn, Uranus, and Neptune, are much larger
and more massive than Earth, and they do not have solid surfaces. Because
these planets are so large and composed of gases, they are commonly referred
to as the gas giants. Like the sun, the gas giants are comprised of mainly
hydrogen and helium.
Because they are so massive, the gas giants have a much larger gravitational
force than the terrestrial planets. This increased gravity prevents the gases of
the planet from escaping, so they have thick atmospheres. Because of the
gravitational pull and thick atmospheres, the pressure inside the planet is
enormous. Thus, the hydrogen and helium comprising the planet is in liquid
form. Because the gas giants are so far from the sun, their outer layers are
extremely cold. But, due to the increased pressure inside the planet,
temperature increased greatly within the planet.
Each gas giant has many moons and is surrounded by a set of rings. A ring is a
thin disk of small particles of ice and rock.
Jupiter
Jupiter is the largest and most massive of the planets. In fact, it is 2 ½ times
larger than all of the other planets combined!
Scientists think that Jupiter, like the other gas giants, probably has a dense
core of rock and iron. This inner core is overlaid by a deep layer of metallic
hydrogen. Jupiter also has four moons: Io, Europa, Genymede, and Callisto.
The outer atmosphere is visibly segregated into several bands at different
latitudes, resulting in turbulence and storms along their interacting
boundaries. A prominent result is the Great Red Spot, a giant storm that is
known to have existed since at least the seventeenth century.
Saturn
The second-largest planet in the solar system is Saturn. Saturn also has a
thick atmosphere made up of helium and hydrogen. Saturn's interior is similar
to that of Jupiter, having a small rocky core surrounded mostly by hydrogen
and helium. The rocky core is similar in composition to the Earth, but denser.
Above this, there is a thicker liquid metallic hydrogen layer, followed by a layer
of liquid hydrogen and helium, and in the outermost 1,000 kilometers (600 mi)
a gaseous atmosphere. Saturn has the most spectacular rings of any planet.
These rings are made up of chunks of ice and rock, each orbiting the planet.
Saturn’s rings are very thin and broad, like a CD with a planet in the hole.
Saturn’s largest moon, Titan, is larger than the planet Mercury. Saturn has at
least 60 moons, but NASA and astronomers are discovering new moons all the
time!
Uranus
Although the gas giant Uranus is about four times the diameter (what’s that?)
of Earth, it is still much smaller that Jupiter or Saturn. Uranus is twice as far
from the sun as Saturn, so it is much colder. Uranus looks blue-green because
of methane in its atmosphere. Uranus’ axis of rotation is tilted about 90˚ in the
vertical, so from Earth it looks like it’s rotating on its side. Compared to Earth,
it takes Uranus 30,799 days or 84 years to orbit the sun! Finally, Uranus has
at least 27 moons that we’ve been able to detect to date – and, like Saturn,
we’re always looking for more!
Neptune
Neptune is even farther from the sun than Uranus. Neptune is a cold, blue
planet. Scientists think that Neptune is slowly shrinking, causing the interior
to heat up. Astronomers have discovered at least thirteen moons orbiting
Neptune, the largest of which is Triton. Neptune’s orbit around the sun takes
approximately 60,327 days. How many years is that? (~165 years)
Images used in this lesson:
Jupiter
Source: http://en.wikipedia.org/wiki/File:Jupiter.jpg
License: Public Domain
Jupiter to Earth Comparison
Source: http://en.wikipedia.org/wiki/File:Jupiter-EarthSpot_comparison.jpg
License: Public Domain
Jupiter’s Interior
Source: http://en.wikipedia.org/wiki/File:Jupiter_interior.png
License: Public Domain
Giant Red Spot
Source:
http://en.wikipedia.org/wiki/File:Great_Red_Spot_From_Voyager_
1.jpg
License: Public Domain
Jupiter Seen Cassini
Source: http://en.wikipedia.org/wiki/File:PIA04866_modest.jpg
License: Public Domain
Saturn as Seen by Cassini
Source:
http://en.wikipedia.org/wiki/File:Saturn_from_Cassi
ni_Orbiter_(2004-10-06).jpg
License: Public Domain
Saturn to Earth Comparison
Source:
http://en.wikipedia.org/wiki/File:Saturn,_Earth_size_compariso
n.jpg
License: Public Domain
Titan
Source:
http://en.wikipedia.org/wiki/File:Titan_in_natural_color_Cassin
i.jpg
License: Public Domain
Saturn with Moons Titan and Tethys
Source:
http://www.titanexploration.com/Titan%20Images/titanimages
2008.htm
License: Public Domain
Uranus
Source: http://en.wikipedia.org/wiki/File:Uranus2.jpg
License: Public Domain
Uranus Rings
Source: http://en.wikipedia.org/wiki/File:Uranusandrings.jpg
License: Public Domain
Uranus with Clouds and Rings
Source: http://en.wikipedia.org/wiki/File:Uranus_clouds.jpg
License: Public Domain
Uranus to Earth Comparison
Source:
http://en.wikipedia.org/wiki/File:Uranus,_Earth_size_comparis
on.jpg
License: Public Domain
Uranus Moons (A montage of Uranus' large moons and one
smaller moon: from left to right Puck, Miranda, Ariel, Umbriel,
Titania and Oberon. Other moons are not yet photographed in
detail. Size proportions are correct.)
Source: http://commons.wikimedia.org/wiki/File:Uranus_moons.jpg
License: Public Domain
Neptune
Source: http://en.wikipedia.org/wiki/File:Neptune.jpg
License: Public Domain
Neptune to Earth size comparison
Source:
http://en.wikipedia.org/wiki/File:Neptune,_Earth_size_comparis
on.jpg
License: Public Domain
The Rings of Neptune
Source: http://en.wikipedia.org/wiki/File:Neptune_ring_arcs.jpg
License: Public Domain
Neptune and Triton
Source:
http://en.wikipedia.org/wiki/File:Voyager_2_Neptune_and_Trito
n.jpg
License: Public Domain