Astronomers Detect X-Rays From Uranus for First Time

April 7, 2021 Updated: April 7, 2021

NASA’s Chandra X-ray Observatory recently spotted X-rays from Uranus, the seventh planet in our solar system, for the first time.

According to a statement from NASA, the new discovery can help scientists learn more about Uranus.

Uranus has a diameter four times that of Earth, and it has two sets of rings around its equator. The planet is mostly made up of hydrogen and helium.

An unusual feature of this planet is that unlike all other planets in our solar system, Uranus rotates on its side.

Voyager 2 was the only spacecraft that ever flew by Uranus. To study this distant planet, astronomers currently rely on ground and space-borne telescopes, including the Chandra X-ray Observatory and the Hubble Space Telescope.

In the new study, researchers used two Chandra observations taken in 2002 and in 2017. They found a clear detection of X-rays from both observations. The second one was more significant, as it might indicate a flare of X-rays.

Why would Uranus emit X-rays? The researchers believe that the reason may be related to the sun, according to the NASA statement.

Previously, astronomers saw that both Jupiter and Saturn scattered X-ray light given off by the sun, just as the Earth’s atmosphere scatters sunlight. A similar mechanism could apply to Uranus.

However, the researchers found hints that another source of X-rays may be present. If confirmed by future observations, this phenomenon could have intriguing implications, according to the statement.

The research team has come up with two possible scenarios for the additional X-ray sources. One is that the rings of Uranus are producing X-rays. If energetic charged particles like electrons and protons collide with the rings, they might cause the rings to glow with X-rays.

Another possibility is that some of the X-rays may come from auroras on Uranus. Such a phenomenon has previously been detected on this planet at other wavelengths.

Auroras on Earth happen when high-energy particles interact with the atmosphere. X-rays are detected in Earth’s auroras as well as Jupiter’s.

However, scientists are less certain about what causes Uranus’s auroras.

The statement explains that Uranus is particularly interesting for X-ray observations because of the unusual orientations of its magnetic field and spin axis. The rotation and magnetic field axes of other planets in our solar system are almost perpendicular to the plane of their orbits around the sun. However, the rotation axis of Uranus is nearly parallel to its orbit.

Moreover, while Uranus is tilted, its magnetic field is tilted to a different degree and is offset from the center of the planet, which may make its auroras unusually complex and variable, the statement explains.

The new findings are reported in a paper in the Journal of Geophysical Research.