Here’s another amazing photo from APOD, Astronomy Picture of the Day, that illustrates how enormous some of the famous nebulae in the sky are, compared to constellations.
As I said in an earlier post not quite a month ago, here, I’d always been under the impression that the amazing galaxies and nebulae we see from telescopic photography were greatly magnified, that to the naked eye they exited in tiny patches of the sky.
But again, this isn’t true: some of these nebulae are enormous, and we don’t see them only because our eyes are optimized (via evolution) for the high and low ends of light we experience here on planet Earth. Other creatures, perhaps, living in darker environments with more sensitive eyes, might look up into the sky and see the photo above.
This photo is a compilation of 40 hours of of deep sky photography, with various photographs aligned into a panorama in the sky above this house. And it helpfully adds lines for the familiar constellations: Orion in the middle, Gemini in upper left, Perseus in upper right. The bright spot in the lower end of Orion is the familiar Orion nebula, barely visible with our human naked eyes; in the upper right, outside a constellation boundary, is the familiar Pleiades cluster. Those are the only two patches of this area of the night sky that are visible to the naked human eye.