The human eye is tuned to a narrow band of wavelengths: visible light. But the electromagnetic spectrum extends far beyond our ability to see – from radio waves to gamma rays. Each slice of the spectrum tells us different things about the universe.

Consider X-rays. We’re most familiar with them in medical settings. But many astronomical objects produce their own X-rays, allowing astronomers to diagnose their details.

The list includes many types of stars. Many stars have hot, X-ray-producing outer atmospheres. Stars also generate big eruptions, known as flares. Studying these events tells us more about how stars age, and how they interact with the universe around them.

X-rays are especially common in some of the most violent objects and events in the universe. Exploding stars heat their environment to millions of degrees – producing X-rays galore. And disks of hot gas around black holes are also X-ray sources. The X-rays can reveal the amount of gas, the size of the disk, and how fast the gas is moving.

There’s one problem, though: Earth’s atmosphere absorbs X-rays. So astronomers loft their telescopes as high as possible. They’ve used rockets, balloons, and a rocket-balloon combination called a rockoon. But most of what we know about the X-ray sky came from space telescopes. The largest and most powerful X-ray telescope to date was launched 25 years ago next week, and we’ll talk about that on Monday.

Script by Damond Benningfield