Getting your questions ready
Getting your questions ready
Beat the crowd
10 questions No timer
50 free White Dwarfs trivia questions with answers — science & nature quiz, new questions added Aug 2026.
A white dwarf is the Sun's mass squeezed into a ball the size of Earth, shining only because it has not yet cooled down. This quiz covers the physics and the history: electron degeneracy pressure and Fowler's 1926 fix, the Chandrasekhar limit and the 1935 row with Eddington, the 'impossible' densities that made astronomers say 'shut up', the matchbox nugget, and the ten billion white dwarfs thought to sit in the Milky Way. It also visits the famous individuals: 40 Eridani B, first to be recognised, Sirius B and Bessel's prediction, van Maanen's lonely star and its 1917 hint of planets, Procyon B, the crystallised 'diamond' star Lucy, the seven-minute spinner ZTF J1901+1458, and WD 1856's giant planet, plus Type Ia supernovae, planetary nebulae, black dwarfs and the coolest, most magnetic and first pulsating examples. Easy questions suit anyone who has read a pop-astronomy book; the expert tier asks for catalogue numbers and spectral types. Every answer was checked against Wikipedia's articles on white dwarfs and the individual stars and scientists, and the supporting sentence is attached to each question. If you like this, try our quizzes on stars and on the Solar System.
30 of 50 questions with answers and explanations. Play the quiz
Q 01A white dwarf packs a mass comparable to the Sun's into a volume roughly the size of what?
Earth
That gives an average density of about a tonne per cubic centimetre.
Q 02What is the source of a white dwarf's light?
Residual heat, not fusion
Once formed, its material no longer undergoes fusion, so it slowly cools and reddens.
Q 03How far away is Sirius B, the nearest known white dwarf?
8.6 ly
It is the smaller partner of the brightest star in the night sky.
Q 04In which year was 40 Eridani B recognised as the first white dwarf?
1910
Russell, Pickering and Fleming found the dim star had a puzzling white A-type spectrum.
Q 05Who coined the name 'white dwarf' in 1922?
Willem Jacob Luyten
Eddington then popularised the term.
Q 06What holds a white dwarf up against gravitational collapse?
Electron degeneracy pressure
It is a quantum effect: the Pauli exclusion principle stops electrons crowding into the same state.
Q 07What is the approximate maximum mass of a non-rotating white dwarf, the Chandrasekhar limit?
1.44 solar masses
Above it, the star can no longer hold itself up and collapses.
Q 08Who published the presently known value of the white dwarf mass limit in 1931?
Subrahmanyan Chandrasekhar
He worked out the degenerate Fermi gas statistics on the ship from India to England in 1930.
Q 09In which year did Chandrasekhar share the Nobel Prize in Physics for his work on stellar structure?
1983
He shared it with William Alfred Fowler.
Q 10Where was Chandrasekhar born?
Lahore
He was born into a Tamil Brahmin family in what is now Pakistan.
Q 11Which physicist resolved the puzzle of white dwarf density in 1926 by applying the new quantum mechanics?
R. H. Fowler
He showed that electrons obeying the Pauli principle would keep the star from collapsing even at zero temperature.
Q 12Which astronomer predicted in 1844 that Sirius and Procyon had unseen companions?
Friedrich Bessel
He guessed the period of Sirius's companion at about half a century.
Q 13Who first observed Sirius B, on 31 January 1862?
Alvan Graham Clark
He was testing a telescope lens when the faint companion appeared.
Q 21What fraction of the Milky Way's stars are expected to end up as white dwarfs?
Over 97%
Everything from about 0.07 to 10 solar masses takes that path.
Q 22A typical white dwarf's radius is what percentage of the Sun's?
0.8 to 2 per cent
That is comparable to our own planet, whose radius is about 0.9 per cent of the Sun's.
Q 23What is the approximate average density of a white dwarf?
One tonne per cubic centimetre
Only neutron stars and hypothetical quark stars are denser.
Q 14Which Dutch-American astronomer discovered the first isolated white dwarf, now named after him, in 1917?
Adriaan van Maanen
With 40 Eridani B and Sirius B it makes up the three 'classical' white dwarfs.
Q 15A 1917 photographic plate of van Maanen's Star gives the earliest known evidence of what?
Planetary material outside the Solar System
Calcium absorption lines showed rocky debris polluting the star's atmosphere.
Q 16How many white dwarfs had been discovered by 1939?
18
By 1999 over 2,000 were known, and a major sky survey has since found over 9,000.
Q 17Who in 1916 calculated 40 Eridani B's density at 25,000 times the Sun's and called it 'impossible'?
Ernst Öpik
Eddington later joked that astronomers' 1914 reply to such densities was 'Shut up. Don't talk nonsense.'
Q 18In Eddington's famous 1927 image, a ton of Sirius B's material would be a nugget that fits in what?
A matchbox
He imagined the star's light carrying the message 'I am composed of material 3000 times denser than anything you have ever come across'.
Q 19Around what mass is the distribution of observed white dwarfs strongly peaked?
0.6 solar masses
Most lie between 0.5 and 0.7 solar masses, though extremes from 0.17 to 1.33 are known.
Q 20Roughly how many white dwarfs are thought to exist in the Milky Way?
Ten billion
Eight sit among the hundred nearest star systems to the Sun.
Q 24A white dwarf accreting matter past the Chandrasekhar limit is the leading model for which event?
A Type Ia supernova
Their uniform brightness makes them standard candles for measuring galaxy distances.
Q 25What is a cooled-down stellar remnant of this kind, no longer radiating, eventually called?
A black dwarf
None are thought to exist yet, since the cooling time exceeds the age of the universe.
Q 26What is the nickname of BPM 37093, a white dwarf whose core is thought to be largely crystallised carbon?
Lucy
The Beatles song 'Lucy in the Sky with Diamonds' inspired it; observations in 2004 suggested about 90 per cent of its mass had crystallised.
Q 27What is the ejected shell of gas that surrounds a newly formed white dwarf called?
A planetary nebula
The name is a misnomer; early telescopes made them look like the disc of Uranus.
Q 28What was the first variable (pulsating) white dwarf found, in 1965–66?
HL Tau 76
It varied with a period of about 12.5 minutes.
Q 29Which white dwarf, identified in 1970, was the first found to have a magnetic field?
GJ 742 (GRW +70 8247)
James Kemp and colleagues detected it from circularly polarised light.
Q 30Roughly what surface temperature has one of the coolest known white dwarfs, WD J2147–4035?
About 3,050 K
Few white dwarfs are seen below 4,000 K.