Quiz, myth or fact, and the approach meter
Test yourself. Every answer comes with its source.
How to play. Pick an answer and the fact behind it appears, with a link to where it comes from. Without JavaScript, open “Show the answer” under each question.
The Andromeda quiz
1 What is Andromeda’s catalogue number in Messier’s list?
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M31. The Andromeda Galaxy, also called M31, is the nearest major galaxy to our own Milky Way. NASA, M31
2 About how far away is Andromeda, says NASA?
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2.5 million light-years. NASA gives its distance as 2.5 million light-years. NASA, M31
3 Who mentioned Andromeda as early as 965 CE?
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al-Ṣūfī. It was mentioned as early as 965 CE in the Book of the Fixed Stars by the Islamic astronomer al-Ṣūfī. Britannica
4 What did Simon Marius say it looked like?
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A candle seen through a horn. Marius said it looked like the light of a candle seen through a horn. Britannica
5 What did Hubble write on his plate in October 1923?
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VAR!. He crossed out the ‘N’ and wrote ‘VAR!’, for variable, with an exclamation mark. NASA, V1
6 What kind of star is V1?
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A Cepheid variable. The star, Hubble variable number one or V1, is a Cepheid variable in Andromeda’s outer regions. NASA, V1
7 How long does V1 take to brighten and fade once?
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A little over 31 days. V1 takes a little over 31 days to brighten and fade once. NASA, V1
8 About how many stars are in Hubble’s 2025 Andromeda panorama?
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200 million. In January 2025 Hubble released an even bigger panorama: about 2.5 billion pixels and 200 million stars. NASA, M31
9 How massive is the black hole at Andromeda’s heart, from 2005 Hubble measurements?
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140 million Suns. In 2005 Hubble measurements put its mass at 140 million Suns, three times more than once thought. NASA, black hole
10 How many small satellite galaxies orbiting Andromeda did Hubble study?
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36. Hubble has studied the whole known population of 36 small satellite galaxies orbiting Andromeda. NASA, 2025
11 What did the 2025 study say about a collision in the next 10 billion years?
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About a 50-50 chance. In 2025 a new study using Hubble and Gaia data found only about a 50-50 chance of the two galaxies colliding in the next 10 billion years. NASA, 2025
12 Which constellation’s W shape points towards Andromeda?
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Cassiopeia. The W-shaped constellation Cassiopeia points towards Andromeda. EarthSky
Myth or fact?
Eight statements. Some are true, some are myths.
1 Andromeda is getting closer to us.
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Fact. Andromeda is getting about 110 km (70 miles) closer to us every second. Royal Observatory
2 When the galaxies meet, stars will smash into each other.
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Myth. Stars are so far apart that they would not hit each other. NASA, 2012
3 You can see Andromeda with your eyes alone from a dark site.
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Fact. It is one of the few galaxies you can see with your eyes alone, as a milky blur. Britannica
4 Andromeda has always been known to be a separate galaxy.
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Myth. For centuries astronomers thought it was part of the Milky Way, a ‘spiral nebula’, hence the old name Andromeda Nebula. Britannica Britannica: only in the 1920s did Hubble show conclusively that Andromeda is a separate galaxy. Britannica
5 In the sky Andromeda looks bigger than the full Moon.
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Fact. It is so close that it looks six times as wide as the full Moon in the sky. NASA, M31
6 Andromeda is a quiet galaxy that has never swallowed another.
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Myth. Andromeda has a past of collisions, swallowing smaller galaxies. Britannica
7 Hubble’s 2025 panorama shows every star in Andromeda.
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Myth. Even 200 million stars is only a fraction of Andromeda’s population. NASA, M31
8 The Andromeda constellation is named after a character in Greek myth.
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Fact. The constellation is named after Andromeda, daughter of Queen Cassiopeia and King Cepheus in Greek myth. EarthSky
The approach meter
Andromeda is coming. Here is how much closer it has got since you opened this page, and over your lifetime.
Andromeda is getting about 110 km (70 miles) closer to us every second. Royal Observatory
Since you opened this page: 0 km closer
Pick an example or type an age.
Our own rough arithmetic: the Royal Observatory’s 110 km a second multiplied by the seconds in your age, compared with NASA’s 2.5 million light-years at 9.46 trillion km per light-year. The meter assumes a straight-line approach, which is a simplification.