Q 01/05

How many planets are in our Solar System?

A) Four

B) Eight

C) Sixteen

D) Thirty-two

Answer · why

B) Eight

Eight have made the list since 2006, when astronomers ruled that a planet must have cleared other objects out of its orbit, a test that Pluto fails.

Q 02/05

The Sun is made mostly of which gas?

A) Oxygen

B) Helium

C) Hydrogen

D) Carbon dioxide

Answer · why

C) Hydrogen

Hydrogen is the Sun's fuel: in the core it is fused into helium, releasing the energy that leaves as heat and light.

Q 03/05

Which planet is closest to the Sun?

A) Venus

B) Mars

C) Mercury

D) Earth

Answer · why

C) Mercury

Mercury is so close that it laps the Sun every 88 days, the fastest of any planet. Yet it turns so slowly that one sunrise-to-sunrise day lasts two of...

Q 04/05

Which planet is the largest in the Solar System?

A) Jupiter

B) Neptune

C) Saturn

D) Earth

Answer · why

A) Jupiter

Jupiter is more than twice as massive as all the other planets put together, yet it spins so fast that its day lasts under ten hours, the shortest of ...

Q 05/05

What is the Great Red Spot on Jupiter?

A) A giant storm

B) A volcano

C) A crater

D) A frozen lake

Answer · why

A) A giant storm

A giant storm that has been spinning for well over a century. It lasts so long partly because Jupiter has no solid ground to slow its winds down.