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60 free Andromeda Galaxy trivia questions with answers — science & nature quiz, new questions added Aug 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.
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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
Four independent methods, averaged, give about 2.54 million light-years.
Q 03The Andromeda Galaxy is described as which type of galaxy?
Barred spiral
Visible-light images suggested an ordinary spiral, but infrared surveys revealed a bar, just like the Milky Way's.
Q 04Andromeda is the largest member, by extent, of which galaxy grouping that also includes the Milky Way?
The Local Group
The group is dumbbell-shaped, with the Milky Way and its satellites in one lobe and Andromeda and its satellites in the other.
Q 05With an apparent magnitude of about 3.4, how can the Andromeda Galaxy be seen from Earth?
With the naked eye on moonless nights
It can be spotted even from areas with moderate light pollution and is one of the most distant naked-eye objects.
Q 06The galaxy's virial mass is estimated at roughly how many solar masses?
1 trillion
It was long thought a quarter to a half heavier than the Milky Way, but recent studies suggest the two are closer to equal, or the Milky Way heavier.
Q 07Which Persian astronomer described the Andromeda Galaxy as a "small cloud" in his Book of Fixed Stars around 964 CE?
Abd al-Rahman al-Sufi
It is the earliest known reference to any galaxy beyond the Milky Way; star charts of the era called it the Little Cloud.
Q 08Which German astronomer gave an early telescopic description of Andromeda in 1612?
Simon Marius
Messier later mistakenly credited him as its discoverer.
Q 09Which philosopher argued in 1755 that elliptical nebulae like Andromeda were island universes similar to the Milky Way?
Immanuel Kant
His book was Universal Natural History and Theory of the Heavens; Maupertuis had made a similar conjecture in 1745.
Q 10William Herschel guessed in 1785 that Andromeda was no more than 2,000 times the distance of which star?
Sirius
That put it at roughly 18,000 light-years, wildly short; he had noted a faint reddish hue in the core.
Q 11Who made a drawing of Andromeda's spiral structure in 1850?
The 3rd Earl of Rosse
His giant reflector, the Leviathan of Parsonstown, had revealed spiral structure in nebulae five years earlier.
Q 12In 1864 William Huggins found that Andromeda's spectrum resembled that of what, rather than a gaseous nebula?
Individual stars
The continuum with dark absorption lines showed the object was made of stars.
Q 13The only supernova ever observed in the Andromeda Galaxy, S Andromedae, appeared in which year?
1885
It was called "Nova 1885" at the time, since the difference between novae and supernovae was not yet understood.
Q 21In 1943 Walter Baade resolved stars in Andromeda's core and divided stars into two populations. What did he name them?
Type I and Type II
His later discovery of two kinds of Cepheids doubled the estimated distance to Andromeda, and to the rest of the universe.
Q 22The estimated distance to Andromeda was doubled in 1953 following what discovery?
A second, dimmer type of Cepheid
Baade found the two Cepheid types while working at Mount Wilson.
Q 23Radio emissions from Andromeda were first detected in 1950 by Hanbury Brown and Hazard at which observatory?
Jodrell Bank
Q 14Which Welsh amateur astronomer took one of the first photographs of Andromeda in 1888?
Isaac Roberts
He mistook Andromeda and similar spiral nebulae for star systems in the process of forming.
Q 15In 1912 Vesto Slipher measured Andromeda's radial velocity at about 300 km/s, the largest yet recorded. Which technique did he use?
Spectroscopy
He went on to discover that most spiral nebulae are redshifted, laying the groundwork for the expanding universe.
Q 16In 1917 Heber Curtis used novae in Andromeda to estimate its distance, in light-years, at about how far?
500,000
About five times too small, but the first estimate correct to within an order of magnitude.
Q 17The 1920 Great Debate over whether spiral nebulae were separate galaxies pitted Heber Curtis against which astronomer?
Harlow Shapley
Curtis argued for island universes and was ultimately proven right on that main point.
Q 18Edwin Hubble settled the debate in 1925 by identifying which kind of star in photographs of Andromeda?
Cepheid variables
Their period-luminosity relation, discovered by Henrietta Leavitt, made them standard candles for measuring distance.
Q 19Hubble's Andromeda photographs were taken with which instrument, then the largest in the world?
The 100-inch Hooker reflector
It sat on Mount Wilson above Los Angeles.
Q 20Which Estonian astronomer estimated Andromeda's distance in 1922 from the velocities of its stars, placing it far outside the Milky Way?
Ernst Öpik
His figure of about 450 kiloparsecs was closer to the truth than Hubble's first result.
The galaxy's core is listed as 2C 56 in the second Cambridge radio catalogue.
Q 24Andromeda's most massive globular cluster, nicknamed Globular One, is catalogued under what name?
Mayall II
It is about twice as luminous as Omega Centauri and may be the stripped core of a swallowed dwarf galaxy.
Q 25Approximately how many globular clusters are associated with the Andromeda Galaxy?
460
Unlike the Milky Way's, they span a wide range of ages, from as old as the galaxy to a few hundred million years.
Q 26What is the designation of the supermassive black hole at Andromeda's centre?
M31*
It is a low-luminosity active nucleus, detected only in radio and X-rays, with a 2005 mass estimate of 110-230 million suns.
Q 27Hubble Space Telescope images in 1991 revealed Andromeda's nucleus to consist of how many concentrations of stars?
Two
Two concentrations, P1 and P2, sit 1.5 parsecs apart; the brighter one is offset from the true centre.
Q 28A 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 29Andromeda's two best-known satellite galaxies are M32 and which other?
M110
M32 seems to have punched through Andromeda's disk more than 200 million years ago, creating its inner dust ring.
Q 30Andromeda's satellite M32 was discovered in 1749 by which French astronomer?
Guillaume Le Gentil
It is a compact dwarf about 2.49 million light-years away.