The universe is photoshopped
Our astronomer points out that that pictures of outer space don’t actually show what you’d see if you went there.
Our astronomer writes:
You’re all familiar with pictures from the Hubble Space Telescope and other great devices: unearthly beauty, glowing clouds of gas in brilliant colors; a recent example comes from the Astronomy Picture of the Day website (well worth visiting every morning). Probably you realize that these are highly magnified pictures of the sky; in fact, as you stand out under the stars at night you could cover the whole view of the HST with your little finger held at arm’s length. So, obviously, you’d have to travel many light-years and get really close before you’d be able to look out your starship porthole and see the same view. But you wouldn’t even then.
One big reason is that surface brightness stays the same, regardless of distance. That is, a white wall seems exactly as bright no matter how far you stand away from it: each little piece gets fainter as you go away, but you see more of them, and the effects exactly cancel out. So these faint nebulae that you can’t perceive with your naked eye from Earth, well, standing right next to them you couldn’t see them either. Telescopes not only magnify the view, but collect more light than your eyes can, making everything brighter.
Because of this, they also make things more colorful. In very low light, your eyes see only black-and-white. (That’s why moonlight seems silvery: it’s the same as sunlight, really, but much fainter, so you don’t see the green of the grass and trees.) In practice, though, it takes a very big telescope to make nebulae bright enough to see colors in.
The HST pictures also make colors more brilliant through electronic manipulation, a basic sort of Photoshop (though it appeared before that program was put together). Astronomers have long taken black-and-white pictures thorugh color filters for various scientific reasons. With separate red, blue and green images you can recombine them to make a standard color picture. But especially if you use very narrow filters, passing only a small range of color, you get brilliant and saturated colors in the final result. And some nebulae have “line emission,” in which an element (hydrogen or oxygen, say) shines only in a very, very narrow range of color, providing a natural sort of filter. The result is beautiful. But it’s not what you’d see with your eye. For instance, you won’t see the blue and pink of this picture of the Milky Way no matter where you view the Galaxy from yourself.
It’s not that NASA, or other astronomers, are deliberately trying to fool you. Although anyone who relies on public funding is well aware of the utility of pretty pictures, the origin of the “photoshopped universe” lies in actual science. An astronomer is really interested in how the (green) oxygen in a nebulae is distributed compared to the (red) hydrogen, so a brilliantly colored picture is useful. Sometimes a bright idea about how you choose to visualize your data is more useful than gathering it in the first place!
So you shouldn’t expect your view through a small telescope (such as I set up on my lawn some nights), or even the night sky as you see it far from city lights, to look like the pictures. It’s different. Smaller, less colorful. But far more real.
