Q 01/05

Which is the largest planet in the Solar System?

A) Jupiter

B) Saturn

C) Earth

D) Neptune

Answer · why

A) Jupiter

Its radius is about 71,000 km, and it sits 5.2 astronomical units from the Sun.

Q 02/05

Which is the smallest planet in the Solar System, and the closest to the Sun?

A) Mars

B) Mercury

C) Pluto

D) Venus

Answer · why

B) Mercury

It orbits between 0.31 and 0.59 astronomical units from the Sun, so its year lasts only 88 Earth days.

Q 03/05

Roughly what share of the Solar System's total mass is the Sun?

A) About 75%

B) About 90%

C) About 99.9%

D) About 50%

Answer · why

C) About 99.9%

Everything else, including all the planets, adds up to well under one percent.

Q 04/05

The asteroid belt lies between the orbits of which two planets?

A) Earth and Mars

B) Venus and Earth

C) Mars and Jupiter

D) Jupiter and Saturn

Answer · why

C) Mars and Jupiter

The dwarf planet Ceres, the largest object in the belt, lives there too.

Q 05/05

Earth's atmosphere is made up mostly of oxygen and which other gas?

A) Carbon dioxide

B) Hydrogen

C) Argon

D) Nitrogen

Answer · why

D) Nitrogen

That gas makes up about four-fifths of the air, with oxygen just under 21%.