Outer Planets

Gas giants -Jovian Planets: •Jupiter •Saturn •Uranus •Neptune

 

The gas planets do not have solid surfaces, their gaseous material simply gets denser with depth

What we see when looking at these planets is the tops of clouds high in their atmospheres.

Jupiterorbit: (5.20 AU) from

Sun

• Jupiter (a.k.a. Jove; Greek Zeus) was the King of the Gods, the ruler of Olympus and the patron of the Roman state

• Zeus was the son of Cronus (Saturn)

   Jupiter

• fourth brightest object in the sky – (after the Sun, the Moon and Venus; at some

times Mars is also brighter).

• It has been known since prehistoric times

In 1610, Galileo discovered Jupiter's four large moons

This was the first discovery of a center of motion not apparently centered on the Earth now known as the Galilean moons

Supported Copernicus's heliocentric theory of the motions of the planets

Galileo's outspoken support of the Copernican theory got him in trouble with the Inquisition

Heliocentric—sun-centered 

Four Moons of Jupiter

• Io--volcanic

• Europa—liquid water???

• Ganymede

• Callisto

Io—the volcanic “pizza” moon

• Io very volcanic because of the gravitational pull of Jupiter on its surface

• Its surface moves in and out about 100 meters

Europa

• Greatest possibility of life

• Possibility of liquid water beneath the icy surface

• This picture shows cracks in the ice

•

Gannymede and Callisto are both highly cratered

• Jupiter is about 90% hydrogen and 10% helium (by numbers of atoms, 75/25% by mass) with traces of methane, water, ammonia and "rock"

• Very close to the composition of the primordial Solar Nebula from which the entire solar system was formed

• Saturn has a similar composition, but Uranus and Neptune have much less hydrogen and helium 

 

9.54 AU from SunGalileo was the first to observe

it with a telescope in 1610In Roman mythology, Saturn is

the god of agricultureSaturn is the root of the English

word "Saturday" Earth passes through the plane

of Saturn's rings every few years as Saturn moves in its orbit.

Saturn

Saturn is the least dense of the planets

• specific gravity (0.7) is less than that of water

–It could Float!!!

• Saturn's interior is hot • Saturn radiates more energy into

space than it receives from the Sun.

Uranus

19.218 AU from Sun

•  Careful pronunciation may be necessary to avoid embarrassment; say "YOOR a nus", not "your anus" or "urine us".

97º tilt

• Most of the planets spin on an axis nearly perpendicular to the plane of the ecliptic but Uranus' axis is almost parallel to the ecliptic.

Uranus' blue color is the result of absorption of red light by methane in the upper atmosphere

How’d it get that name?

Uranus is the ancient Greek deity of the Heavens, the earliest supreme god.

The name "Uranus" was first proposed by Bode in conformity with the other planetary names from classical mythology but didn't come into common use until 1850

Composition of Uranus

• composed primarily of rock and various ices • only about 15% hydrogen and a little helium in

contrast to Jupiter and Saturn which are mostly hydrogen

• Uranus (and Neptune) similar to the cores of Jupiter and Saturn – minus the massive liquid metallic hydrogen envelope

• Uranus does not have a rocky core like Jupiter and Saturn but rather that its material is more or less uniformly distributed

Uranus' atmosphere is about 83% hydrogen, 15% helium and 2% methane   

Uranus is sometimes just barely visible with the unaided eye on a very clear night; it is fairly easy to spot with binoculars (if you know exactly where to look)

Neptune

0.06 AU from Sun

• In Roman mythology Neptune

(Greek: Poseidon) was the god of the Sea

• Neptune's winds are the fastest in the solar system, reaching 2000 km/hour   Methane gas atmosphere

Eccentric orbit

Because Pluto's orbit is so eccentric, it sometimes crosses the orbit of Neptune making Neptune the most distant planet from the Sun for a few years

Eccentricity

• How squished the elliptical orbit is

Neptune’s Discovery

• After the discovery of Uranus, it was noticed that its orbit was not as it should be in accordance with Newton's laws. It was therefore predicted that another more distant planet must be perturbing its orbit.

• Perturbation--Variation in an orbit due to the influence of external bodies

– Retrieved from "http://en.wiktionary.org/wiki/perturbation" 

Pluto

• Pluto is the farthest planet from the Sun (usually) by far the smallest.Pluto

•So. . . a day is longer than a year

Pluto and Charon

Pluto and Charon

• Pluto’s moon• Discovered July

1978

• Covered with water ice instead of nitrogen ice

• 1/7 the size of Pluto

Important Terms

• Eccentricity—how squished the elliptical orbit is (how oval the oval is)

• Period—one revolution around the sun

• Heliocentric—the sun is the center of the solar system

• Geocentric—the Earth is the center of the solar system