The Outer Planets

THE OUTER PLANETS

1.WHAT ARE THE OUTER PLANETS?

Ans: The outer planets are Uranus, Neptune and Pluto, and Pluto’s companion Charon. Unlike the other planets,these were completely unknown to ancient astronomers. They are so far away, and so faint, that Uranus was discovered only in 1781, Neptune in 1846,Pluto in 1930 and Charon as recently as 1978. Uranus and Neptune are gas giants like Jupiter and Saturn.

2. WHAT’S STRANGE ABOUT URANUS?

Ans: Unlike any of the other planets, Uranus does not spin on a slight tilt. Instead it is tilted right over and rolls around the Sun on its side, like a giant bowling ball.

3. WHAT’S AN ASTEROID?

Ans: Asteroids are the thousands of rocky lumps that circle round the Sun in a big band between Mars and Jupiter. The biggest,Ceres, is 640 km across.Most are much smaller,Over 5000 asteroid shave been identified so far.

4. WHAT IS A COMET?

Ans: Comets are really just dirty ice balls. Normally, they circle the outer reaches of the solar system. But occasionally, one of them is drawn in towards the Sun. As it hurtles towards the Sun, it melts and a vast tail of gas is blown behind it by the solar wind. We may see this spectacular tail in the night sky shining in the sunlight for a few weeks until it swings round the Sun and out of sight. The Hale-Bopp comet gave a spectacular display in 1997.

5. WHO FOUND NEPTUNE?

Ans: Two mathematicians, John Couch Adams in England and Urbain le Verrier in France, predicted where Neptune should be from the way its gravity disturbed Uranus’s orbit. Johann Galle in Berlin spotted it on September 23, 1846.

6. HOW LONG IS A YEAR ON NEPTUNE?

Ans: Neptune is so far from the Sun- over 4,500 million km that its orbit takes about 165 Earth years. So one year on
Neptune lasts 165 Earth years.

7. WHY IS NEPTUNE GREEN?

Ans: Neptune appears greeny-blue because of the methane gas (a component of natural gas) in its atmosphere.

8. HOW BIG IS PLUTO?

Ans: Pluto is very small, which is why it was so hard to spot. It is five times smaller than the Earth just 2,390 km across and 500 times lighter.

9. WHAT IS A METEORITE?

Ans: Meteorites are lumps of rock from space big enough to penetrate the Earth’s atmosphere and reach the ground without burning up.