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Uranus is the seventh planet in our solar system - counting from the center.

Like the two giant planets Jupiter and Saturn, icy Uranus is surrounded by rings.

The diameter of Uranus, which consists mainly of hydrogen and helium, is about four times larger than that of our earth.

One property distinguishes Uranus from all other planets in our solar system: it lies on its side.

This means that its axis of rotation is not roughly perpendicular to the plane of the orbit, but tilted by almost 90 degrees.

Because its two ring systems are above the equator, they too are tilted at approximately a right angle relative to the rings of Saturn.

The Uranus rings could play a role in the observation that NASA researchers made with the "Chandra" space telescope.

This research satellite was the first to detect X-rays on Uranus.

"Chandra" and the diffuse splash of color

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Since the Nasa space probe "Voyager 2" flew by in 1986, the planet has not received a visit from Earth.

At that time, ten moons of Uranus were discovered.

Since then, astronomers have been exploring the distant planet exclusively with telescopes on Earth and those that are in orbit - including "Chandra" and the "Hubble" space telescope.

The X-rays registered by “Chandra” appear on the images as a diffuse splash of color.

An international research team led by William Dunn from University College London presents in the "Journal of Geophysical Research" the superimposition of these X-ray hotspots with an optical image of Uranus obtained with the W. M. Keck Observatory in Hawaii.

This made it possible to locate the position of the X-ray source near the equator of Uranus.

But how does this X-ray radiation come about?

The researchers suspect that the rings of Uranus and their unusual location play a role in this.

Finally, a tilted axis of rotation also means a tilted magnetic field.

They assume that the Uranus radiation cannot be explained solely by the X-ray light emitted by the sun, which is reflected or scattered at Uranus.

This effect occurs on every planet in our solar system, also on Earth and certainly also on Uranus.

But that can't be all.

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The researchers have two possible explanations in mind.

Like other planets, Uranus is surrounded by electrically charged particles such as protons and electrons.

When these high-speed particles collide with particles in the two Uranus rings, high-energy X-rays should be generated.

Another possibility would be that effects such as those that lead to the formation of polar lights on other planets also enable X-rays to be emitted from Uranus.

In the end, all three effects could have their share in the X-ray glow of Uranus.

In fact, the terrestrial northern lights also produce a little X-ray radiation.

This is also known from the giant planet Jupiter.

In both Earth and Jupiter, electrons circle along the magnetic field lines and also emit X-ray light.

Another mechanism is added to Jupiter.

In its polar regions, positively charged atoms and molecules “rain” down, generating X-ray light.

The authors of the current study are still unsure which of the possible processes and to what extent are responsible for the X-ray glimmer.

And if scientists do not understand something exactly, then they want to continue research, clarify the open questions and understand Uranus better.

For the time being, they still describe the observations of "Chandra" as a mystery.