Snapshot: Chandra discovers X-rays from Uranus

In a first, scientists have seen X-ray light coming from one of our solar system’s most mysterious planets. The question is: Why?
By | Published: April 8, 2021 | Last updated on May 18, 2023
X-ray and optical image of Uranus
X-ray: NASA/CXO/University College London/W. Dunn et al; Optical: W.M. Keck Observatory

Located in the outer reaches of the solar system, Uranus is a strange planet. Only one spacecraft — Voyager 2 — has ever visited, so astronomers know relatively little about the distant world. Already the odd one out by spinning on its side, now Uranus has revealed another strange feature: It’s emitting X-rays, and astronomers aren’t sure why.

Astronomers recently took a new look at observations of Uranus made by the Chandra X-ray Observatory in 2002 and 2017. Both showed X-rays coming from the seventh planet from the Sun. The image above shows X-rays detected in 2002 in pink on a visible-light image (blue and white) of the planet.

Researchers believe what’s happening at Uranus is something that happens at Jupiter and Saturn as well. Uranus’ atmosphere may simply be scattering X-rays from the Sun, rather than producing the light itself. But another possibility is that the rings are producing the X-rays, much like the rings of Saturn. Still other scientists speculate the X-rays could come from aurorae on Uranus.

But even aurorae would be a mystery, as scientists aren’t sure what could cause them on the ice giant. Because Uranus rotates on its side, its magnetic field is also tilted. This could create some complex aurorae — if they occur. For now, astronomers are hoping that Chandra may shed more light on one of the strangest planets in our solar system.