UranusNeptune

And their moons

Uranus StatisticsRadius: 3.98 times Earth’s (25,559 km)Mass: 14.54 times Earth’s (8.68 x 10^25 kg )Density: 1.32 g/cm³ ( 23 % of Earth’s)Surface Gravity: 8.69 m/s² (88.6 % Earth’s)

Orbit and RotationRadius (average.): 19 AU (2,749,000,000 km )Year: 84 Earth Years Sidereal Day: 17.24 Hours Axial Tilt: 97.86º (Earth’s: 23.45°)

Neptune’s StatisticsRadius: 3.81 times Earth’s (24,764 km )Mass: 17.13 times Earth’s (1.02 x 10^26 kg )Density: 1.64 g/cm³ ( 30 % of Earth’s)Surface Gravity: 11.15 m/s² ( 114% Earth’s)

Orbit and RotationRadius (average.): 30.06 AU (4,496,000,000

km )Year: 164.8 Earth Years Sidereal Day: 16.11 hours Axial Tilt: 29.56º (Earth’s: 23.45°)

Uranus and Neptune True Twins

They are gas giants like Jupiter made mostly of Hydrogen and its compounds, chiefly H2O.

About the same size color and structure, Uranus and Neptune are true twins.

But both have large amounts of methane in their atmosphere that absorb red making them appear blue

Their interiors have a large layer of compressed water around their cores.

Effects of Uranus’ Tilton the path of the Sun

For a person at a Pole the “daytime” (or summer) lasts 42 years

When summer begins the Sun rises circles just above the horizon, then for 21 years it gradually circles higher and higher.

Finally it follows a circle about 8° from Zenith. Then it spirals out, in larger and larger circles for 21

more yearsIt only sets because of the change of seasons, and

night (or winter) lasts another 42 years!

Why Uranus is Monochrome and Tilted

As a result of the extreme tilt at its “midsummer” a Pole points nearly directly at the Sun.

The resulting unusual solar heating of the atmosphere may explain the lack of cloud bands found on the other gas giants.

Uranus’s extreme tilt is thought to be due to either:• a collision with a large planetismal or • the Gravity of nearby planets, mostly Saturn.

Uranus Discovery and RingsUranus was unknown to the ancients. It was

discovered by Sir William Herschel in 1781 though at first he thought it was a comet

Uranus has a complex ring system like Saturn

But thinner.In 1789 Herschel first saw

a ring but was unsure.In 1977 the rings were

confirmed to exist

Uranus’ MoonsIt has at least 27 Moons,Including five larger onesThe two largest Titania and

Oberon were discovered by Herschel

The Fifth largest, Miranda seems to have been shattered and then been reassembled

Only 472 km in radius it has a giant cliff 15 km high!That’s like one about 203 km (122 miles) high on

Earth!

The Discovery of NeptuneNeptune was unknown to ancients.Galileo saw it in 1613 while looking at Jupiter’s

moons but didn’t know what it wasIn the 1840’s two astronomers noticed a perturbation, that is a slight change in Uranus’ orbit due to the

gravity of an undiscovered planet.One was English …one French.A German using the French calculations spotted it in

1846. For decades both France and England claimed credit

for the discovery

NeptuneNeptune is a denser version of

Uranus. It has thin ringsIt has more methane in its

atmosphere making it a deep blue.

As it has a normal axial tilt it has faint cloud bands

Winds on Neptune are particularly fast 2200 km/h!

…powered by an internal heat source.

That also makes it emit more heat than it gets.

Like Jupiter it has a large long lasting storm

The Great Dark Spot.

Triton and other MoonsNeptune has at least

six small moons.The largest, Triton

orbits “backward”And is probably a

captured Dwarf planet from the Kuiper belt.

It has a “wrinkled” cantaloupe-like terrain. Geysers of nitrogen, water ice and carbon driven by

the Sun’s heat leave dark streaks like soot. Voyager detected such an eruption