APOD Shuffle

Random thoughts inspired by NASA's Astronomy Picture of the Day (APOD):

• Orion Nebula: This picture shows how the Orion Nebula looked 1500 years ago. Or, well, at least how it would look if we could see in infrared. But, really, it's only 1500 years on average. Stuff in the front of the picture sent that light out more recently than stuff in the back. The whole sky works that way. We see Proxima Centauri as it was a mere 4 years ago, while we see the Andromeda Galaxy as it was about 2.5 million years ago. If we somehow constructed a map of where the stars are right now and how bright they are, it would look different than the sky we're used to. Not only would some stars be missing and some new stars be added, but everything is also moving relative to one another. Those things that we see as they were 2.5 million years ago likely are quite a ways away from where we see them, for example.


• Horsehead-shaped nebula: This beautiful image of a horse's head (not to be confused with the Horsehead Nebula) is also a great example of the strange and interesting phenomenon called pareidolia. Humans are pattern-seeking creatures, so when we look at things, we try to assign them to categories. We look at this nebula, and we see a horse's head. We look at a hill on Mars,and we see a face (and some continue to do so even when a second photo shows that the resemblance in the first photo was coincidental). And, of course, some people look at a grilled cheese sandwich, see a shape that looks vaguely like a human female, and assume it's the Virgin Mary.


• Lagoon Nebula: Why couldn't whoever runs the APOD at NASA take the 5 minutes to make those two pictures line up (mouse over the picture to see what I mean)? Sigh. Still beautiful.


• 3D galaxy: It's amazing to me that that's a photo; strangely, it looks too real to me for me to immediately accept that it's really a photo. It's the kind of shot you might create for Star Trek credits or something. That galaxy is about 50 million light years away, but remember: the front edge isn't quite as far away (and therefore not as far in the past) as the back edge. However, compared to the total distance, the 30 thousand light year diameter of the galaxy is almost nothing.