Q 01/05

A neutron star is the gravitationally collapsed core of what kind of object?

A) A white dwarf

B) A gas giant planet

C) A massive supergiant

D) A globular cluster

Answer · why

C) A massive supergiant

Stars that end up as neutron stars typically start out with 10 to 25 times the mass of the Sun.

Q 02/05

Roughly what is the radius of a typical neutron star?

A) About 1,000 kilometres

B) About 10 kilometres

C) About the radius of the Moon

D) About the radius of the Sun

Answer · why

B) About 10 kilometres

That is roughly the size of a city, yet the star packs in around 1.4 times the mass of the Sun.

Q 03/05

Which class of objects is the only one denser than neutron stars?

A) Black holes

B) Quasars

C) White dwarfs

D) Brown dwarfs

Answer · why

A) Black holes

Neutron stars are the second-smallest and second-densest known class of stellar objects.

Q 04/05

What kind of event compresses a stellar core into a neutron star?

A) A solar flare

B) A planetary nebula

C) A supernova explosion

D) A tidal disruption

Answer · why

C) A supernova explosion

The core is squeezed past white-dwarf density all the way to the density of atomic nuclei.

Q 05/05

About how many neutron stars are thought to exist in the Milky Way?

A) Around ten thousand

B) Around one million

C) Around one trillion

D) Around one billion

Answer · why

D) Around one billion

The estimate comes from counting how many stars have gone supernova, and most of them have long since cooled and gone dark.