Myths

Myths and big questions

Ten common ideas about our galaxy, checked against the sources.

How this site works. Every fact is in our own words and linked to its source, beside it. Where good sources disagree, we show each version in a “Sources differ” box.

1. MythThe Milky Way is the whole universe.

   FactBased on the deepest images so far, ours is one of about 2 trillion galaxies in the observable universe. NASA, how big Only in the 1920s was it confirmed that many nebulous ‘stars’ were whole other galaxies far beyond our own. Library of Congress

2. MythWe are at the centre of the galaxy.

   FactNASA: Earth sits along one of the spiral arms, about halfway from the centre. NASA, galaxies In 1917 Harlow Shapley used globular clusters to show the galaxy is immense, about 100,000 light-years across, with the Sun nearer the edge than the centre. Britannica, structure

3. MythWith your eyes you can see the colours from photos.

   FactWith your eyes alone you won’t see the colours in photos: the Milky Way looks like fuzzy, colourless patches of light in a rough strip. Royal Observatory, naked eye

4. MythThose pictures of the whole Milky Way are photos taken from outside.

   FactNo spacecraft has gone far enough to photograph the Milky Way from outside, so every picture of the whole galaxy is an artist’s impression or a data map. Royal Observatory

5. MythSpiral arms are made of the same stars for ever.

   FactArms don’t keep the same stars. ESA’s Jos de Bruijne compares them to traffic jams: stars leave at the front while more pile up at the back. ESA, Gaia

6. MythThe black hole at the centre will swallow Earth.

   FactNASA puts it 26,000 light-years away, and says there is no danger of Earth being pulled in. NASA, 10 questions

7. MythWhen Andromeda arrives, stars will smash into each other.

   FactStars are so far apart that they would not hit each other, but the Sun would probably be thrown much farther from the centre. NASA, 2012

8. MythA collision with Andromeda is certain.

   FactIn 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 It left only about a 2% chance of a head-on collision in just 4 to 5 billion years. NASA, 2025

9. MythYou need a telescope to see the Milky Way.

   FactUK Dark Sky Discovery Sites come in two grades: at “Orion” sites you can see the seven main stars of Orion; at “Milky Way” sites, much darker and found only in rural areas, the Milky Way is visible to the naked eye. Dark Sky Discovery From them you can see the Milky Way, and the Andromeda Galaxy, with your eyes alone. Visit Isle of Man

10. MythThe Milky Way is a smallish galaxy, and we know exactly how big.

    FactIts precise shape, true size and mass are still not known. Britannica, summary Until dark matter is pinned down, the total mass can’t be measured: it is at least several hundred billion, and possibly a trillion, times the Sun’s. Britannica, structure

Big open questions

Its precise shape, true size and mass are still not known. Britannica, summary

Later Gaia star maps gave clear evidence for four arms, an ESA scientist says. ESA, Gaia

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

Until dark matter is pinned down, the total mass can’t be measured: it is at least several hundred billion, and possibly a trillion, times the Sun’s. Britannica, structure