What Makes A Star Starry? Is It Me?

Notice what Tyler Nordgren does in these posters. He's an artist, an astronomer (from Cornell, Carl Sagan's department); he's worked for NASA. He's an expert in dark matter, and a full professor at the University of Redlands. He knows much, much more than I do about astrophysics and stars, and yet, look at these night skies — a series he created to promote America's national parks at night ...

The stars aren't right. They're supposed to be pointy, with little beams coming off them.

That's how we usually see stars. But not here ...

Courtesy of Tyler Nordgen

Or here ...

Courtesy of Tyler Nordgren

Nordgren makes his stars round. Like planets. His recent poster series, "Half the Park is After Dark," was an enormous popular and artistic success. The posters, with their 1930s graphic style, are gorgeous. But, why the roundness? Or maybe I should upend the question and ask, How come we always draw our stars pointy? Is it because we actually see them that way? When I look up at night, stars do look different from planets. They have a "starry" (that is, diffracted, or spiky) shape. Maybe that's because they are far away. The one exception is the only star that's very close, our sun. We know it is round. But we also know, if we think about it, that all the other stars are round, too. They're giant balls of plasma, "balls" being the key word. So where does the pointedness come from?

Well, here, gloriously, is the answer. It comes from Henry (sometimes Radiolab, mostly Minute Physics) Reich, who discovers that if 7 billion of us were to look up at a single star, that star would have 7 billion slightly different shapes. Each one of us has his or her own sky: