International Space Station astronaut Karen Nyberg has tweeted some amazing photos from space over the past few weeks, but this one may be the most remarkable, and she may not have even noticed why when she took it! [UPDATE: She did notice; see below.]
The picture above shows sunrise as seen from 400 kilometers (250 miles) above the Earth, our planet’s silhouette just beneath the overexposed curve of our atmosphere. The Sun is a mix of reddish colors, the blue and green light scattered away from it by particles in the air. What makes this image immediately special, though, is the quiet presence of the Moon, a thin crescent, off to the right. The Moon is a waning crescent, meaning its nearing the end of it's monthly orbital cycle, the lit part we see shrinking every day as the apparent distance between the Moon and the Sun dwindles.
But we’re not done. I wanted to see if I could tell just when this picture was taken, so I fired up some astronomy software to see where the Moon was today—it turns out the photo was taken just a few hours ago as I write this, very probably in the afternoon (UTC) on Sunday, August 4, 2013.
But I noticed that, according to the my software, Mercury was in the sky between the Moon and Sun. Wondering if it would be visible in the photo, I cranked up the brightness and saw not only what I’m pretty sure is Mercury, but also another bright “star” that I strongly suspect is Jupiter!
The positions and brightnesses all match, so I think we have a hit. The two planets should have been visible by eye from the space station, but the glare from the bright Sun may have swamped them, which may be why Nyberg didn’t mention them. Once I post this article I’ll tweet it to her; if she responds I’ll write an update!
UPDATE (18:15 UTC on Aug. 4, 2013): I sent a tweet to Nyberg, and she responded: "@BadAstronomer @NASA I DID see Jupiter & Mercury & was disappointed when I didn't see them in my photo. Thanks! Took this ~11:20 GMT today." Here's the whole conversation:
OK, wow, so today just got a lot cooler.