March 7 2014 7:45 AM

The Big Dipper Like You’ve Never Seen It Before

By Phil Plait
 

Rogelio Bernal Andreo is an astrophotographer. But calling him that seriously underplays what he does: He’s an artist. His photos of the sky, especially the wide-angle ones covering entire constellations, are incredible. He made a portrait of Orion so magnificent that words fail me, but I did my best when I chose it as the top astronomy photograph of 2010.

Of course, Orion is an amazing target; it’s loaded with stars, gas clouds, dark clouds, and other beasties of the night. But it turns out that Andreo is just as talented when it comes to what you might think is a more boring section of the sky: the Big Dipper.

The Big Dipper, a familiar sight to star gazers. But there are jewels hidden there ... click to hugely embiggen.

Photo by Rogelio Bernal Andreo, used by permission

Sure, when you see it here you can pick out the stars of the dipper and not much else. But that’s because I had to shrink it a lot to fit the blog. The original full-resolution image is a staggering 7000 x 3074 pixels and is amazing. It’s a 24-frame mosaic Andreo took in early summer 2011 in central California, where skies can get very dark.

I’d like to note first that, technically, the dipper isn’t a constellation; it’s an asterism, a close collection of stars that form a pattern. Constellations are bigger and are official, like the borders of states. The Big Dipper is actually part of Ursa Major, the big bear—the bowl of the dipper is the bear’s haunches, and the handle is the tail (which is itself funny: Bears don’t have tails). The asterism is near the north pole of the sky, so it’s easily seen by anyone north of the Equator.

Interestingly, while the stars in the dipper don’t form a proper constellation by themselves, most of them are actually physically associated! Except for Dubhe (at the far end of the bowl) and Alkaid (the tip of the handle), all the stars are part of the same cluster, called the Ursa Major cluster, and are moving through space together. The stars are all about 80 light years away, and are spread out over a trail some 30-light-years long. How about that?

Andreo’s photo shows remarkable detail. Of course there are thousands of stars, but I was able to see dozens of galaxies as well. A few of them are quite famous, like the huge and beautiful M101, the Pinwheel Galaxy:

The spiral galaxy M101 and the nearby nebula M97.

Photo by Rogelio Bernal Andreo

M101 hosted a bright supernova back in 2011, incidentally. Near the galaxy in the sky (though not in reality) is the planetary nebula M97, the Owl Nebula, which you can see to the galaxy’s lower left. M101 is 25 million light years away, while the Owl is about 2500. The galaxy 10,000 times farther away!

As an avid sky watcher myself, I knew about those objects (and a few others, like the spiral galaxy M109). What surprised me was on the right, in the bowl of the dipper:

Feathery dust glows near the bowl of the dipper.

Photo by Rogelio Bernal Andreo

See that glow? That’s very faint dust, called galactic cirrus (or less fancifully, an Integrated Flux nebula, which is pretty cool too). It’s very common around the north celestial pole, but so dim it’s unusual to see. Andreo’s mosaic captured it beautifully. I knew the cirrus existed, but it had slipped my mind, so seeing it in the picture was a pleasant and interesting surprise.

And that, I suppose, is my point. I’ve seen the Big Dipper thousands of times, perused it by eye, with binoculars, and through a telescope. And yet, even in a wide-field picture like this, there are still treasures to be found there. Just because something is familiar doesn’t necessarily mean you truly know it.

Tip o' the lens cap to another great astrophotographer, Brad Goldpaint.