Deep view of Andromeda galaxy beautifully shows the vastness of space

I have been doing astronomy stuff my whole life, and it has been years since I last got a genuine spine-shiver from contemplating the vastness. I am pretty jaded. But this did it, the zoomable version of this photo:

That is the most detailed image ever taken of the Andromeda galaxy, by Hubble of course. The original is a 70,000-pixel-wide photo. The lo-res version here is 800 pixels wide, so the original contains approximately 7500 times more information, 7500 times more detail than what you can see at this size.

So you can really zoom in. For that experience, visit the “zoomable” version of the image.

Andromeda is a galactic neighbour to the Milky Way. If galaxies were the size of houses, these two would be a few blocks apart. So it’s “close” in astronomical terms (but still stupidly far of course, 2.5 million light-years).

When we see the glow of a galaxy, it’s mostly the combined light of an insane number of stars we’re seeing, not individual stars. In fact, many of the “individual” points of light visible in this photo not stars, but vast symmetrical “globular” clusters of hundreds of thousands of stars. This is true of most pictures of near-ish galaxies: their globular clusters look like individual stars. But in this image, you can actually zoom in and watch a “point” of light turn into an uncountable swarm of stars.

Dizzying. In a good way.

In the zoomable version of the photo, start zooming in on “stars” until you find one that resolves into lots of stars. Here’s one example:

That’s a little bit hard to believe, so here’s a little more visual information to confirm it:

Many other bright points of light here are actually stars, but they are in the foreground, in the Milky Way… and some are stars in Andromeda that are extremely bright. Weirdly, there’s no easy way to tell the difference. From our vantage point, there is effectively no difference between an insanely bright star at a great distance, a much dimmer one that’s nearby, or a medium-brightness star at a medium distance! Astronomers have ways of distinguishing them in most cases, but it’s basically impossible just from the photo.