Imagine we could travel to the Andromeda Galaxy and look back at our own Milky Way Galaxy.
What would the Andromeda Galaxy look like if we could actually travel there now, and how would Earth and our Solar System appear when viewed from that distance?
The issue with predicting what the Andromeda Galaxy would like if we could travel there is that the cosmic limit of the speed of light means we can only know what a body was like at the time the light we see set off from it.
This is why when we look at the night sky, we're actually looking back in time.
The Andromeda Galaxy is 2.5 million lightyears away, so it’s impossible to know what it was like more recently than 2.5 million years ago.
However, imagine that we could see it as it is right now.
The difference of 2.5 million years is only about 1/5,000th the life span of Andromeda, and galaxies barely change on such time scales.
For instance, the Sun only travels about 2% of the way round the Milky Way in this time.
So Andromeda would look the same, except that a few hundred thousand stars that we can see in telescopes will have died, while a similar number will have been born.
What would Earth and the Solar System look like?
So we've travelled to the Andromeda Galaxy and pointed our telescopes back at our own Milky Way Galaxy. What would the Sun and Earth look like?
In general, the stars that make up the constellations visible from Earth (the ones that appear brightest in our skies) are less than a thousand lightyears away.
The stars that make up the pattern of a constellation are often very far away from each other, and only appear close together from Earth’s perspective.
If you could journey to the closest star, Proxima Centauri, the Sun would appear as a bright star in the W-shaped constellation Cassiopeia.
However, if you start going much further, the patterns of stars will shift and the constellations become distorted and then unrecognizable.
If you voyaged all the way to the Andromeda Galaxy and looked back at the Milky Way, our own Galaxy would appear as a small spiral, but the Sun and Earth would be impossible to spot among the billions of other stars that make up one of its spiral arms.
