Andromeda Galaxy Trivia
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56 free Andromeda Galaxy trivia questions with answers — science & nature quiz, new questions added Oct 2026.
This Andromeda Galaxy trivia quiz covers the nearest major galaxy to our own, from the smudge al-Sufi drew in 964 to the 600-field Hubble mosaic of 2025. The easy questions are the ones any stargazer knows: its Messier number, how far away it is, which constellation it sits in, whether you can see it without a telescope, and what is supposed to happen when it meets the Milky Way. From there it moves into the history of working out what it actually was, the Great Debate of 1920, and how Edwin Hubble finally settled the argument with Cepheid variables on the Hooker telescope. The hard end is for people who read the papers: the only supernova ever seen in it, the double nucleus imaged by Hubble in 1991, the supermassive black hole M31*, the ring of fire, Globular One, the possible extragalactic planet, the microquasar, and why the collision odds were revised down to about fifty-fifty in 2025. There is also a short run on the princess the constellation is named after. Every answer was checked against Wikipedia's articles on the galaxy, its satellites, its constellation and the astronomers who studied it, and each question links to the page that establishes it. Fifty questions, free, with an explanation after every answer.
30 of 56 questions with answers and explanations. Play the quiz
Q 01What is the Andromeda Galaxy's number in Charles Messier's catalogue?
M31
Messier logged it in 1764 and wrongly credited a German astronomer with discovering an object visible to the naked eye.
Q 02Roughly how far from Earth is the Andromeda Galaxy?
2.5 million light-years
2.5 million light-years. That means the glow you can see tonight left Andromeda about 2.5 million years ago, long before our own species existed.
Q 03The Andromeda Galaxy is described as which type of galaxy?
Barred spiral
Barred spiral. Dust hid the bar in ordinary photographs, so it took near-infrared surveys in the 2000s, which see through the dust, to pick out the boxy central bulge that gives a bar away.
Q 04Andromeda is the largest member, by extent, of which galaxy grouping that also includes the Milky Way?
The Local Group
The Local Group. Mutual gravity holds its galaxies together, which is why Andromeda is falling toward the Milky Way while far-off galaxies rush away from us.
Q 05At a minimum, how can the Andromeda Galaxy be seen from Earth?
With the naked eye on moonless nights
With the naked eye on moonless nights, no instrument is needed, which is why skywatchers had put it on star charts centuries before the telescope was invented.
Q 06With more than twice the Milky Way's star count, Andromeda holds roughly how many stars?
1 trillion
1 trillion. More stars need not mean more weight, though: several estimates of its total mass put Andromeda level with the Milky Way or lighter.
Q 07In the 10th century, the Persian astronomer al-Sufi made the first known record of Andromeda, describing it as what?
A little cloud
A little cloud. Eight centuries later Charles Messier still credited the discovery to a German astronomer who had merely turned a telescope on it.
Q 08Which rival of Galileo named Jupiter's four big moons and first described Andromeda through a telescope?
Simon Marius
Simon Marius. He and Galileo each claimed to have found the moons first, and Galileo accused him of plagiarism, yet the names Marius chose, Io, Europa, Ganymede and Callisto, are the ones that stuck.
Q 09Which philosopher argued in 1755 that elliptical nebulae like Andromeda were star systems similar to the Milky Way?
Immanuel Kant
Immanuel Kant. He reasoned that the Milky Way itself, seen from far enough away, would look just as small and faint, so the nebulae astronomers kept finding could be other Milky Ways.
Q 10William Herschel guessed in 1785 that Andromeda was no more than 2,000 times the distance of which star?
Sirius
Sirius. Herschel judged the distance from the nebula's colour and brightness, and his guess fell more than a hundred times short of the real figure.
Q 11In 1864 William Huggins found that Andromeda's light, split into colours, resembled that of what, rather than a gaseous nebula?
Individual stars
Individual stars. Glowing gas shines in a few bright lines, but Andromeda's light spread into a continuous band like starlight, an early hint that the 'nebula' was really a vast crowd of suns.
Q 12What was S Andromedae, which blazed up in Andromeda in 1885?
A supernova
A supernova. In 1885 nobody knew such explosions existed, so it was logged as an ordinary nova, and no one grasped that they had watched a star blow up in another galaxy.
Q 13The reddish patches that dot Andromeda's disc in photographs are star-forming regions glowing with which gas?
Hydrogen
Q 21Walter Baade's 1950s discovery that Hubble's yardstick stars were not all alike did what to Andromeda's estimated distance?
Doubled it
Doubled it. Every other galaxy's distance grew along with Andromeda's, so the whole universe turned out twice as big, and older, than astronomers had believed.
Q 22Radio emissions from Andromeda were first detected in 1950 by Hanbury Brown and Hazard at which observatory?
Jodrell Bank
The galaxy's core is listed as 2C 56 in the second Cambridge radio catalogue.
Q 23What did the Hubble Space Telescope find at Andromeda's centre in the early 1990s?
A double nucleus
A double nucleus. It is now thought to be an illusion: the two clumps look like parts of one lopsided disc of old stars circling the central black hole, not two separate clusters.
Hydrogen. Fierce light from newborn stars sets the gas around them glowing, so the red patches work as a map of where Andromeda is still making stars.
Q 14Which technique did Vesto Slipher use in 1912 to clock Andromeda at about 300 km/s, the greatest speed then measured?
Spectroscopy
Spectroscopy. Slipher read the speed from the way the lines in Andromeda's light were displaced, then found most other such nebulae racing away, the first clue that the universe is expanding.
Q 15In 2012 NASA predicted that Andromeda would collide with the Milky Way in about how long?
4 billion years
4 billion years. The first crash would only be the start: the simulations had the pair taking about 2 billion more years to settle into a single galaxy.
Q 16In the 1920 Great Debate, Heber Curtis argued that nebulae like Andromeda were separate galaxies against which rival astronomer?
Harlow Shapley
Harlow Shapley. He had just shown that the Sun lies far from the Milky Way's centre, but he made our galaxy so vast that he thought it held every nebula, Andromeda included.
Q 17Edwin Hubble settled the debate over Andromeda's distance in 1925 by identifying which kind of star in photographs of it?
Cepheid variables
Cepheid variables. These stars pulse at a rate set by their true brightness, so timing one in Andromeda gave Hubble its distance, which was far too great to fit inside the Milky Way.
Q 18Hubble's Andromeda photographs were taken with which instrument, then the largest in the world?
The 100-inch Hooker reflector
The 100-inch Hooker reflector. Having used it to prove Andromeda lies outside our galaxy, Hubble turned the same telescope on fainter galaxies and found that the universe is expanding.
Q 19Vera Rubin's measurements of how fast stars orbit in Andromeda's outskirts became key evidence for what?
Dark matter
Dark matter. Rubin and Kent Ford expected the outer stars to dawdle, as distant planets do around the Sun, but they circled as fast as the inner ones, as if held by unseen mass.
Q 20Which wartime measure helped Walter Baade photograph Andromeda's core in new detail in 1943?
Blackouts in Los Angeles
Blackouts in Los Angeles. With the city dark below his mountaintop observatory, he could at last make out the faint red stars in Andromeda's heart, and saw that galaxies hold two distinct populations of stars.
Q 24A prominent band of gas and dust about 32,000 light-years from Andromeda's core, where most of its star formation happens, is nicknamed what?
The Ring of Fire
Infrared images suggest the whole galaxy may be turning into a ring galaxy.
Q 25Andromeda's two best-known satellite galaxies are M32 and which other?
M110
M110. Charles Messier first saw it beside Andromeda in 1773 and drew it there, yet never listed it, and only in the 1960s did astronomers make it the 110th and last entry in his catalogue.
Q 26Isaac Roberts took one of the first photographs of Andromeda in the 1880s and suggested it showed what being born?
A planetary system
A planetary system. Andromeda was then taken for a nearby nebula, so Roberts read his picture as a sun and its planets condensing, when he had in fact photographed a whole galaxy of stars far beyond our own.
Q 27The 'Andromeda paradox', in which two passers-by disagree on whether an alien fleet has already launched, illustrates which theory?
Special relativity
Special relativity. Roger Penrose's point was that merely strolling toward or away from Andromeda shifts your 'now' there by days, so the two walkers disagree about what has already happened.
Q 28After Andromeda and the Milky Way, which is our neighbourhood's third-largest galaxy?
Triangulum Galaxy
Triangulum Galaxy. It lies close enough to Andromeda that it may be its companion, and some forecasts have it joining any future pile-up between the two giants.
Q 29Andromeda is one of the few galaxies moving toward us, so its light arrives shifted toward which colour?
Blue
Blue. Almost every other galaxy's light is stretched toward red as the universe expands, but Andromeda is falling toward the Milky Way at roughly 110 kilometres a second.
Q 30A 2025 study found the long-forecast collision of Andromeda and the Milky Way to be what?
Only about a coin toss
Only about a coin toss. In 100,000 simulated futures the pair merged in only about half, partly because a smaller neighbour tugs the Milky Way out of Andromeda's path.