Q 01/05

Where does Neptune rank in distance from the Sun?

A) Ninth

B) Eighth

C) Seventh

D) Sixth

Answer · why

B) Eighth

Since Pluto's 2006 demotion it has been the outermost planet, about 30 times farther from the Sun than Earth.

Q 02/05

Neptune is unique among the planets in how it was found. How?

A) It was predicted mathematically before being seen

B) It was found by a spacecraft

C) It was spotted by an amateur

D) It was found on an old photograph

Answer · why

A) It was predicted mathematically before being seen

Wobbles in Uranus's orbit told Adams and Le Verrier where to look.

Q 03/05

Who first observed Neptune through a telescope, on 23 September 1846?

A) John Couch Adams

B) Johann Gottfried Galle

C) Urbain Le Verrier

D) William Herschel

Answer · why

B) Johann Gottfried Galle

He found it within a degree of Le Verrier's predicted position on the very night the letter arrived.

Q 04/05

Which two mathematicians independently predicted Neptune's position from Uranus's orbit?

A) Laplace and Lagrange

B) Gauss and Bessel

C) Newton and Halley

D) Adams and Le Verrier

Answer · why

D) Adams and Le Verrier

A Franco-British row over credit followed; the consensus now is that both deserve it.

Q 05/05

Whose 1821 tables of Uranus's orbit first revealed that something unknown was tugging on the planet?

A) Pierre-Simon Laplace

B) Friedrich Bessel

C) Alexis Bouvard

D) George Airy

Answer · why

C) Alexis Bouvard

His hypothesis of an unseen perturbing planet set Adams and Le Verrier to work after his death.