Mysterious X-rays Seen Coming From Uranus

There are some stories you tell because they describe amazing discoveries. There are others you tell because you love the double-entendre headline. Some are both. This is one of them. Is there intelligent life on Uranus – the cold planet whose name everyone except astronomers love to mispronounce? That’s just one of the possible explanations for the first X-rays ever seen emanating from Uranus. Get your giggles out of your system now because this is a baffling astronomy mystery from an already strange planet.

“In the new study, researchers used Chandra observations taken in Uranus in 2002 and then again in 2017. They saw a clear detection of X-rays from the first observation, just analyzed recently, and a possible flare of X-rays in those obtained fifteen years later. The main graphic shows a Chandra X-ray image of Uranus from 2002 (in pink) superimposed on an optical image from the Keck-I Telescope obtained in a separate study in 2004. The latter shows the planet at approximately the same orientation as it was during the 2002 Chandra observations.”

Of the planets in the solar system, only Uranus and Neptune have not shown X-rays. A team of astronomers decided to take a closer look at the closer one using archived data from NASA’s Chandra X-ray Observatory and previously unpublished data from NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR). A press release on their study and analysis, published in the Journal of Geophysical Research, shows the earlier image in a composite photo.

Uranus (credit: NASA)

The pink spot is the glow of X-rays from Uranus. For planets closer to the Sun, the main cause of X-rays like these are simple reflections of X-rays from the Sun with particles being scattered by the planet’s atmosphere. Saturn has this phenomena as well as rings, which are suspected of creating X-rays when electrons and protons in its nearby space environment collide with the rings. You can miss the rings in the above picture of Uranus. However, scientists also say X-ray glows can be caused by auroras which form when charged particles travel down magnetic field lines, like on Earth, or they fall on polar regions, as on Jupiter. Uranus has also show auroras, but their cause has not been determined. So, which is causing the X-rays emitting from Uranus? It could be because of its strange angle.

“Uranus is an especially interesting target for X-ray observations because of the unusual orientations of its spin axis and its magnetic field. While the rotation and magnetic field axes of the other planets of the solar system are almost perpendicular to the plane of their orbit, the rotation axis of Uranus is nearly parallel to its path around the Sun. Furthermore, while Uranus is tilted on its side, its magnetic field is tilted by a different amount, and offset from the planet’s center. This may cause its auroras to be unusually complex and variable.”

Animated GIF showing Uranus’ magnetic field. The yellow arrow points to the Sun, the light blue arrow marks Uranus’ magnetic axis, and the dark blue arrow marks Uranus’ rotation axis.
Credits: NASA/Scientific Visualization Studio/Tom Bridgman

Is the orientation of Uranus the cause of its X-rays? If that’s not it, is it intelligent life sending a message to stop staring at Uranus? And to cool it with the jokes because that’s not what they call themselves?

The only way to find out is to continue to probe Uranus – the study points out that there’s more Chandra data to analyze — and a couple of future telescopes, the European Space Agency’s Advanced Telescope for High Energy Astrophysics (ATHENA) due to launch in 2031 and NASA’s Lynx X-ray Observatory mission still under consideration, will be better able to zoom in on Uranus.

Neptune doesn’t emit X-rays either but no one seems to be rushing to probe it or just stare at it for long periods. Perhaps a name change would help. Belly-Button?

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