The birch tree down the road where I live is riddled with holes from the peckings of a yellow-bellied sapsucker, a type of woodpecker. Photo: Bob King
I don’t know what it is about patterns but they sure can make our eyes smile. We’re drawn to them, especially ones that repeat or contrast strongly against a backdrop. All those holes in the birch tree, no doubt the handiwork of a yellow-bellied sapsucker, form a visually arresting pattern. The sapsucker pecks out distinctive holes through the bark in search of sap. When it finds some, the bird gathers it in its beak and tips its head back to drink. Though I’ve never seen a sapsucker there, the distinctive rows leave a record of its presence.
Even where there are no obvious patterns, we imagine them anyway, like the human faces and animal forms among the clouds of a summer afternoon. Our brains are built to seek out patterns because they help us make sense of where we live.
Striking patterns exist among the stars that make our brains hum for explanations. Galactic spiral arms, Saturn’s nested rings, the bulleyes of multiple-ring craters all excite our curiosity and tease us to explain how they got there. Einstein’s Cross is one of those. You’ll find it inside a faint galaxy in the constellation of Pegasus the Winged Horse. Buried inside the core of this galaxy is a gravitationally-lensed quasar. Whoa! What is that?
Einstein’s Cross, the group of four star-like points in the center of the galaxy, is a distant quasar whose light has been split into four images by the "lens" of the galaxy’s core or nucleus. Photo: J. Rhoads, S. Malhotra, I. Dell’Antonio /NOAO/WIYN/NOAO/NSF
Quasars are extremely distant galaxies that look just like stars. The "star" we see is really the last gasp of light and energy given off as real stars and gas get sucked down the throat of a huge black hole in the galaxy’s center.
Einstein’s Theory of Relativity predicted that gravity bends light very much like a lens bends light to create an image. While the sun can bend starlight a wee bit, an entire galaxy has considerable drawing power. For a primer on this, see last week’s blog.
The photo shows four separate, nearly equal points in the galaxy’s core gathered around a small spot that marks the galaxy’s center. Although the center is just a bit of fuzz, it’s composed of millions of stars, and by good fortune happens to lie precisely in front of the much more distant quasar. The gravity of all those stars acts like a powerful lens. When light from the quasar, located 8 billion light years away, encounters the core’s gravity field, it not only gets bent but split into four separate images all symmetrically arrayed around the galaxy’s nucleus. The separate images even flicker in brightness from day to day as particular stars in the galaxy briefly pass in and out of the line of sight.
Repeating patterns are found everywhere in nature. Tiny water droplets just a few millimeters across cling to the tips of each serration along a leaf’s edge after Monday night’s rain. Photo: Bob King
The chance of an alignment like this is exceedingly rare but we live in a big universe where just about anything is possible. Patterns near and far. As we seek to understand them, we’re taken on a journey to places we never could have imagined.