White Dwarfs Trivia
0Loading crowd target
0Loading crowd target
6correct to beat the crowd
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
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 02What makes a white dwarf shine?
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 billions of years.
Q 03Sirius B now weighs less than Sirius A; what about at birth?
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 that outlived it.
Q 04Which astronomer's famous 'new star' of 1572 is now known to have been an exploding white dwarf?
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 blown apart.
Q 05Which NASA space telescope's data revealed, in 2015, a white dwarf tearing apart a small rocky world?
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 of its own worlds apart.
Q 06What holds a white dwarf up against gravitational collapse?
Electron degeneracy pressure
Electron degeneracy pressure is a quantum effect rather than heat: electrons refuse to be squeezed into the same state, so the star stays propped up even after it has gone cold.
Q 07What is the approximate maximum mass of a non-rotating white dwarf, the Chandrasekhar limit?
1.44 solar masses
1.44 solar masses is the ceiling: every white dwarf weighed so far comes in under it, and a dead star left any heavier cannot stay a white dwarf at all.
Q 08The 19-year-old Chandrasekhar did the key calculation behind his mass limit on a 1930 voyage to study at which university?
Cambridge
Cambridge was his destination: on the ship from India he added relativity to the theory of white dwarfs and found that it set a ceiling on their mass.
Q 09Chandrasekhar's 1983 Nobel Prize honoured his studies of what?
The evolution of stars
The evolution of stars and their structure: the citation reached back to work he began as a student, though by 1983 he had long since moved on to the mathematics of black holes.
Q 10Which city, now in Pakistan, was Chandrasekhar's birthplace?
Lahore
Lahore was only a posting: his father was auditing the railways there, and the Tamil family later settled in Madras, where Chandrasekhar went on to study physics.
Q 11R. H. Fowler solved the white dwarf density puzzle in 1926 using the exclusion principle named after which physicist?
Wolfgang Pauli
Wolfgang Pauli's exclusion principle let Fowler explain how so dense a star resists collapse; four years later Fowler took on a research student named Chandrasekhar.
Q 12Which astronomer deduced in 1844, from a wobble in Sirius's path, that it had an unseen companion?
Friedrich Bessel
Friedrich Bessel worked from the bright star's wavering track alone; nearly two decades passed before anyone actually set eyes on the faint companion he had predicted.
Q 13Which American telescope maker first spotted the faint companion of Sirius?
Alvan Graham Clark
Q 21About 97% of our galaxy's stars end as white dwarfs; which are the exception?
The most massive ones
The most massive ones, born with more than about eight to ten Suns of material: their cores grow too heavy to settle as white dwarfs, so they end in collapse and explosion instead.
Q 22What do astronomers call the flare-up when gas stolen from a companion ignites on a white dwarf's surface?
A nova
A nova: the stolen gas piles up until it ignites in a runaway blast on the surface, yet the dead star underneath survives, and some systems have been seen to erupt again and again.
Q 23Which of these objects is even denser than a white dwarf?
A neutron star
Alvan Graham Clark was not hunting for it: he chose Sirius only as a bright point of light for checking a large new lens his family firm had made, and saw a speck beside it.
Q 14Which Dutch-American astronomer discovered the first isolated white dwarf, now named after him, in 1917?
Adriaan van Maanen
Adriaan van Maanen's find at first passed for an ordinary star a little hotter than the Sun; only later was it recognised as a dead star.
Q 15A 1917 spectrum of a nearby white dwarf is now seen as the earliest evidence of what?
A planetary system beyond ours
A planetary system beyond ours: the plate shows calcium, magnesium and iron that should have sunk from view long ago, so rocky debris must still be falling onto the star.
Q 16Gas pulled from a companion star usually gathers into what around a white dwarf before falling in?
An accretion disc
An accretion disc: the stolen gas carries too much sideways motion to fall straight in, so it circles the white dwarf, where friction heats it and lets it spiral down to the surface.
Q 17Sirius is the Dog Star; what nickname do astronomers give its white dwarf companion, Sirius B?
The Pup
The Pup sounds young, but the name misleads: Sirius B is a dead star, a dim ember that takes a telescope to pick out of its brilliant partner's glare.
Q 18In a famous 1927 image, a ton of Sirius B's material would be a nugget that fits in what?
A matchbox
A matchbox: the lecturer who coined the image admitted that when the star's light first carried this message in 1914, most astronomers answered 'Shut up. Don't talk nonsense.'
Q 19What happens to a white dwarf's size as its mass goes up?
It shrinks
It shrinks: the extra gravity crushes the matter tighter, so the heaviest white dwarfs are the smallest, the reverse of how ordinary stars behave.
Q 20Before it becomes a white dwarf, a star like the Sun first swells into what?
A red giant
A red giant: in about five billion years the Sun will balloon until it swallows Mercury and Venus, then puff its outer layers away and leave only its hot core behind.
A neutron star is denser because the squeeze has gone a step further: protons and electrons are crushed together into neutrons, packing a Sun's worth of matter into a ball the width of a city.
Q 24A white dwarf pushed toward the Chandrasekhar limit, by a companion's gas or a merger, can ignite as which event?
A Type Ia supernova
A Type Ia supernova destroys the star outright, and because these blasts peak at nearly the same brightness, astronomers use them to gauge distances to far-off galaxies.
Q 25What name is given to a white dwarf that has cooled until it no longer glows?
A black dwarf
A black dwarf is still only a prediction: cooling that far takes much longer than the 13.8 billion years the universe has existed, so not one is thought to have formed yet.
Q 26BPM 37093, a white dwarf thought to have a crystallised carbon core, has which Beatles-inspired nickname?
Lucy
Lucy, from 'Lucy in the Sky with Diamonds': its discoverers joked that grading this gem would take a jeweller's loupe the size of the Sun, whose own core is expected to crystallise one day.
Q 27What is the ejected shell of gas that surrounds a newly formed white dwarf called?
A planetary nebula
A planetary nebula has nothing to do with planets: the name stuck because the round, glowing shells looked like planets' discs to observers using early telescopes.
Q 28Asteroseismology probes the inside of a white dwarf by measuring what?
Its rhythmic flickering
Its rhythmic flickering: some white dwarfs ring like gongs, and the pattern of beats reveals what lies hidden inside them, much as tremors reveal the interior of our own planet.
Q 29Why are white dwarfs called 'white'?
The first few found were white
The first few found were white, and the name stuck, but they are not all that colour: as the stars cool over billions of years their glow slides from blue-white toward yellow and orange.
Q 30Because white dwarfs cool at a known rate, the faintest ones in a star cluster reveal what about it?
Its age
Its age: the coolest white dwarfs have been fading the longest, so they work as clocks, and even the oldest still glow faintly, which sets a floor under the age of the universe.