Stars
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100 free Stars trivia questions with answers — science & nature quiz, new questions added Oct 2026.
A star is a ball of plasma held together by its own gravity and lit by nuclear fusion in its core. The Sun is one; the observable universe holds something like a million billion billion more, though only about 4,000 can be seen with the naked eye. Almost every element heavier than lithium, including the iron in your blood, was forged inside one. These 100 questions cover the life cycle and the science: molecular clouds and protostars, the main sequence, red giants, planetary nebulae, white dwarfs, supernovae, neutron stars and black holes. You will meet the spectral classes from O to M, the magnitude scale, the Hertzsprung–Russell diagram, the proton–proton chain and the triple-alpha process. The history questions run from Babylonian catalogues and the Chinese supernova of 185 AD to Bessel's first parallax, Annie Jump Cannon's classification and Cecilia Payne's discovery that stars are mostly hydrogen. There are record-holders too: the nearest star, the oldest, the biggest in the sky, the fastest spinner and the smallest that still fuses. Easy questions stick to the Sun and the basics; the expert tier asks about Bok globules, the Hayashi track and who first measured a star's diameter. Every answer is cited and explained.
30 of 100 questions with answers and explanations. Play the quiz
Q 01The few thousand stars visible to the naked eye all lie within which galaxy?
The Milky Way
The Milky Way. Stars in other galaxies are far too distant to pick out one by one, so even on the darkest night the eye catches only a few thousand of our own galaxy's nearest and brightest.
Q 02The Big Bang made hydrogen, helium and a trace of which element, leaving stars to forge nearly all the rest?
Lithium
Lithium. The Big Bang's burst of fusion was over within minutes as the universe cooled, long enough to build only the very lightest nuclei, so heavier elements had to wait for stars.
Q 03Which English word for a catastrophe comes from the Italian for "ill-starred"?
Disaster
Disaster. It joins dis- to astro, "star", because astrologers once blamed a sudden misfortune on an unfavourable position of the planets.
Q 04Ancient Egyptians watched for the dawn return of which star because it heralded the Nile's annual flood?
Sirius
Sirius. Its first dawn appearance came like clockwork just before the flood each summer, so Egyptians worshipped the star as Sopdet, the goddess who brought the new year and the flood.
Q 05Which astronomers were the first to record a supernova, in 185 AD?
Chinese
Chinese. Their astronomers logged a "guest star" that lingered for about eight months, and four space telescopes have since matched it to RCW 86, a glowing shell of debris in the southern sky.
Q 06The supernova of 1054 gave birth to which famous object?
The Crab Nebula
The Crab Nebula. Skywatchers in 1054 saw the blast as a new star bright enough to show in daytime for about three weeks, and the cloud it flung out is still expanding.
Q 07Which galaxy did the Persian astronomer al-Sufi record as a "little cloud" in his Book of Fixed Stars?
The Andromeda Galaxy
The Andromeda Galaxy. Al-Sufi's note of 964 is its first known record, yet nobody knew the smudge was a separate galaxy until Edwin Hubble measured its distance in the 1920s.
Q 08Who suggested in 1584 that stars were suns that might have their own planets?
Giordano Bruno
Giordano Bruno. He pictured an infinite universe of countless worlds, and the Roman Inquisition, which tried him for heresy, had him burned at the stake in 1600.
Q 09Who discovered that some paired stars are true physical companions, or binaries?
William Herschel
William Herschel. He tracked double stars hoping their shifts would reveal their distances, but after 25 years of watching he found that some pairs were instead circling each other.
Q 10Who made the first direct measurement of a star's distance, in 1838?
Friedrich Bessel
Friedrich Bessel. He chose the dim star 61 Cygni because it drifted across the sky faster than any other he had charted, guessing rightly that it must be close, then caught its tiny yearly shift.
Q 11Which star in the Big Dipper's handle was the first known spectroscopic binary?
Mizar
Mizar. Harvard astronomers saw a dark line in its spectrum split in two and merge again, betraying a pair of stars too close together for telescopes of the day to separate.
Q 12Who made the first measurement of a star's diameter, in 1921?
Albert Michelson
He used an interferometer on the Hooker telescope at Mount Wilson.
Q 13The Hertzsprung–Russell diagram plots a star's luminosity against which other property?
Temperature
Temperature. Ejnar Hertzsprung and Henry Norris Russell drew the plot independently around 1911–13, and the patterns stars made on it became astronomers' main tool for working out how stars age.
Q 21Which stars burn their fuel so slowly that they could shine for trillions of years?
Red dwarfs
Red dwarfs. They are so thrifty that not one has ever died of old age: at 13.8 billion years, the universe is still far too young for even the earliest of them to have run dry.
Q 22Astronomers call all elements heavier than helium what?
Metals
Metals. To an astronomer even oxygen and carbon count as metals, and because stars are what forge them, the very first stars are thought to have held virtually none.
Q 23When its core hydrogen runs out in about five billion years, the Sun will swell into what kind of star?
A red giant
Q 14Whose 1925 PhD thesis first proposed that stars are mostly hydrogen and helium?
Cecilia Payne-Gaposchkin
Cecilia Payne-Gaposchkin. The eminent Henry Norris Russell told her the result was "clearly impossible", so she played it down in print; four years later he reached the same conclusion himself.
Q 15Which astronomer labelled stars in each constellation with Greek letters around 1600?
Johann Bayer
Johann Bayer. He was a lawyer rather than a working astronomer, yet the lettering scheme in his 1603 atlas Uranometria caught on so well that astronomers still use it four centuries later.
Q 16Which well-known nebula is a stellar nursery where new stars are forming?
The Orion Nebula
The Orion Nebula. It is the closest large star-forming region to Earth, which is why it can be spotted without a telescope as the fuzzy middle "star" of the hunter's sword.
Q 17The Pillars of Creation, towering columns of star-forming gas photographed by Hubble, lie in which nebula?
The Eagle Nebula
The Eagle Nebula. Its columns stand several light-years tall, yet the fierce light and winds of young stars nearby are slowly wearing them away even as new stars form inside.
Q 18A star spends about 90% of its life in which stage, steadily fusing hydrogen in its core?
The main sequence
The main sequence. It ends when the core runs out of hydrogen: with nothing left to hold it up, the core starts to collapse and heat, and the star's outer layers slowly puff up.
Q 19Stars twinkle because their light is distorted on its way through what?
Earth's atmosphere
Earth's atmosphere. Layers of air at different temperatures bend a star's pinpoint of light this way and that, while planets, which show tiny discs, usually shine steadily.
Q 20How long is the Sun expected to live in total?
10 billion years
10 billion years. That long life comes from modest size: heavier stars hold more fuel but burn it so fiercely that the biggest are gone within a few million years.
A red giant. Estimates of how far it will swell run from about 100 to 250 times its present width, enough to engulf Mercury and Venus and possibly Earth as well.
Q 24What is the explosive onset of core fusion in an ageing low-mass star called?
Helium flash
Helium flash. In heavier stars helium fusion starts gently, but a Sun-like star's core is packed so tightly that it cannot expand to cool itself, so the burning runs away.
Q 25A dying low-mass star ejects its outer layers to form what?
A planetary nebula
A planetary nebula. The name is a mistake that stuck: through early telescopes these glowing shells looked like the round discs of planets, though they have nothing to do with them.
Q 26Very massive stars that shed their outer layers become what kind of star?
Wolf–Rayet
Wolf–Rayet. The type is named after Charles Wolf and Georges Rayet, who found the first ones from Paris in 1867; it is a brief phase that only some massive stars pass through before they explode as supernovae.
Q 27Fusion stops releasing energy once a massive star's core starts producing which element?
Iron
Iron. Fusing it soaks up energy instead of releasing it, so the core abruptly loses the pressure holding it up, collapses in on itself and sets off a supernova.
Q 28Which star's 19th-century "Great Eruption" was a supernova impostor event?
Eta Carinae
Eta Carinae. In the 1840s it briefly became the second-brightest star in the sky while hurling off some ten Suns' worth of gas, a blast that should have torn it apart, yet it survived.
Q 29A stellar remnant below about 1.4 solar masses becomes what?
A white dwarf
A white dwarf. It crams roughly a Sun's worth of matter into a ball the size of Earth, and with no fusion left to heat it, it simply cools and fades over billions of years.
Q 30What is the nearest star to Earth after the Sun?
Proxima Centauri
Proxima Centauri. Despite being our closest neighbour it is far too faint to see without a telescope, so it went unnoticed until 1915; a planet found in 2016 orbits in its habitable zone.