Q 01/05

On which planet does a single rotation take longer than a full trip around the Sun?

A) Venus

B) Mercury

C) Mars

D) Uranus

Answer · why

A) Venus

A Venusian sidereal day lasts 243 Earth days, while its year is only about 225.

Q 02/05

Which planet is the only one in the Solar System less dense than water?

A) Jupiter

B) Saturn

C) Neptune

D) Uranus

Answer · why

B) Saturn

It is about 30 percent less dense than water despite being 95 times Earth's mass.

Q 03/05

Because of its 3:2 spin-orbit resonance, one sunrise-to-sunrise day on the innermost planet lasts how long?

A) Half of its year

B) One of its years

C) Two of its years

D) Four of its years

Answer · why

C) Two of its years

That works out to roughly 176 Earth days from one sunrise to the next.

Q 04/05

A matchbox full of neutron-star material would weigh roughly how much?

A) 3 million tonnes

B) 30,000 tonnes

C) 3 trillion tonnes

D) 3 billion tonnes

Answer · why

D) 3 billion tonnes

That is about the mass of a half-cubic-kilometre chunk of the Earth's crust.

Q 05/05

The molecular cloud Sagittarius B2 near the Milky Way's centre contains large amounts of what?

A) Alcohol

B) Gold

C) Diamonds

D) Liquid water

Answer · why

A) Alcohol

It holds ethanol, methanol and vinyl alcohol, plus ethyl formate, the ester that gives raspberries their flavour.