Sharpest ever view of the Andromeda Galaxy (2015)
Two things are amazing (to me) about this picture.<p>1) When you look up in the sky at the Andromeda Galaxy, your retina is absorbing photons that have been screaming through space for 2.5 million years. If you were on the Earth then, you'd be hanging out with Smilodon, the saber-toothed cat. For 2.5 million years, those photons were freely zooming through space and time, and when you see them, those photons are gone forever, their energy powering a chemical reaction in the rods and cones lining your retina that enables you to see them. <i>Those ancient photons</i> were seen by <i>nobody else</i> but you, and they literally become <i>a part of you</i>.<p>2) In about 3.75 billion years, the Andromeda Galaxy, currently zipping through space toward the Milky Way Galaxy at 110 km/s (nearly 70 miles per second, or about 250,000 MPH), will collide with and merge with our galactic home. It's unlikely anything would happen to the majority of planetary systems in either galaxy (there's a lot of empty space in there) -- but the night sky (not from Earth, we'd probably be cooked by the Sun by then) sure would be beautiful. And bright.<p>Scientists even proposed the name for the new galaxy: Milkomeda.