Why Is There a Hole on the Sun?

By Casey Chan on at

To be honest, this image looks a helluva lot more like an eyeball or a marble than the glowing fiery orange orb floating in our sky that we call the Sun. But nope, it's our Sun all right. It looks off because the image was captured through three of NASA's Solar Dynamics Observatory's extreme ultraviolet filters. But what's up with that gaping hole?

The hole is a coronal hole, areas of the Sun that are darker and colder than normal. The ginormous dark hole is the largest coronal hole that's been observed in over a year. We see a hole in the Sun because that's what the SDO sees. NASA explains:

Coronal holes are the source of strong solar wind gusts that carry solar particles out to our magnetosphere and beyond. They appear darker in extreme ultraviolet light images (here, a combination of three wavelengths of UV light) because there is just less matter at the temperatures we are observing in.

It's like changing the look of a picture with an Instagram filter! But something way more advanced than just that. NASA expects the massive coronal hole to generate some aurora down on Earth. [NASA via Discovery]