Uranus

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The following questions were answered by astronomer Dr. Cathy Imhoff of the Space Telescope Science Institute.

How far is Uranus from the sun?
Uranus is 19 times farther from the sun than Earth is. That is almost 2,000,000,000 (two billion) miles!

Why is Uranus so cold and why is it blue?
Uranus is so cold because it is so far from the sun. It is 19 times farther from the sun than Earth is. It's like standing by a fire on a cold day — only the people who are close to the fire stay warm!

Uranus looks blue because of its clouds. The methane in the clouds absorbs red light so only blue light is reflected back to us.

Why is Uranus turned on its side?
That's a very good question! It isn't easy to turn a planet onto its side. Our best guess is that early on, when the sun and planets were forming, there was a big collision between Uranus and another body that caused the planet to rotate on its side.

What is the weather like on Uranus?
First of all, it is COLD. The surface temperature is about –300° Fahrenheit degrees! There are strong winds, and sometimes cirrus clouds made up of methane ice crystals are seen in the atmosphere. Since Uranus is tipped on its side, it has strange seasons. For part of its "year," the north pole is pointed at the sun, and for another part, the south pole is pointed at the sun. The planet rotates pretty fast — once every 17 hours — faster than Earth even though it is much smaller.

What is the temperature on the surface of Uranus?
The surface temperature of Uranus is very cold, about –300° Fahrenheit. It's pretty cold out there in the outer solar system!

How close could you get to Uranus before you'd sink in?
I don't know the exact answer to this one! Gravity would pull you in, but at some point the thick clouds would act like an ocean and give you some buoyancy (meaning that you would float).

Mercury
Why does Mercury have such extreme temperature differences and Earth does not? Astronomer Cathy Imhoff answers students' questions about the planet Mercury

The Moon
How far is the moon from the Earth? Why does the moon change its shape (as in full, half, and quarter moon)? Astronomer Cathy Imhoff answers students' questions about the moon.

Moon Shadow
Learn what happens when the moon passes directly between the Earth and the Sun: a total solar eclipse.

LESSON PLAN	Lesson 2: Phases of the Moon In this lesson and worksheet, students learn about basic moon phases, and then color in sections of moon according to its pattern.
ONLINE ACTIVITY	The View from Hubble See what the Hubble Space Telescopes sees in this slide show.