Q 01/05

A white dwarf packs a mass comparable to the Sun's into a volume roughly the size of what?

A) Earth

B) The Moon

C) Jupiter

D) A city

Answer · why

A) Earth

Earth is the usual yardstick: with a Sun's worth of matter in a planet-sized ball, a white dwarf's surface gravity runs to 100,000 times ours or more.

Q 02/05

What makes a white dwarf shine?

A) Hydrogen fusion in its core

B) Leftover heat from its past

C) Helium fusion in a shell

D) Friction from its rapid spin

Answer · why

B) Leftover heat from its past

Leftover heat from its past is all it has: fusion in its core has stopped, so a white dwarf simply glows like an ember, fading and reddening over bill...

Q 03/05

Sirius B now weighs less than Sirius A; what about at birth?

A) A was heavier

B) Equal twins

C) B was heavier

D) B formed later

Answer · why

C) B was heavier

B was heavier, perhaps five Suns or more, so it burned through its fuel first and then shed most of its bulk, leaving a faint cinder beside the star t...

Q 04/05

Which astronomer's famous 'new star' of 1572 is now known to have been an exploding white dwarf?

A) Galileo Galilei

B) Tycho Brahe

C) Nicolaus Copernicus

D) Edmond Halley

Answer · why

B) Tycho Brahe

Tycho Brahe's star is long gone, but in 2008 astronomers caught its light still echoing off dust clouds and read in it the signature of a white dwarf ...

Q 05/05

Which NASA space telescope's data revealed, in 2015, a white dwarf tearing apart a small rocky world?

A) TESS

B) Kepler

C) Spitzer

D) WISE

Answer · why

B) Kepler

Kepler recorded the star dimming every 4.5 hours as a crumbling mini planet crossed its face, the first time anyone had watched a dead star tear one o...