Astronomers first detected X-rays from Uranus using NASA’s Chandra Observatory. The new data will help scientists learn more about this giant planet of ice.
Uranus is the seventh planet from the Sun with two sets of rings around the equator. The planet, which is four times the diameter of the Earth, rotates on its side. This distinguishes it from all other planets in the solar system. Since Voyager 2 was the only spacecraft to ever fly past Uranus, astronomers today rely on telescopes much closer to Earth. For example, they are using data from the Chandra X-ray Observatory and the Hubble Space Telescope to learn about this distant and cold planet, which is made up almost entirely of hydrogen and helium.
In the new study, the researchers used Chandra’s observations made in 2002 and then again in 2017. The data has only recently been analyzed. In 2002 data, astronomers found X-rays and their possible flare 15 years later.
The image below shows an X-ray image of Uranus from the 2002 Chandra Observatory (in pink), superimposed on an optical image taken by the Keck telescope during a separate survey in 2004. The planet is approximately in the same orientation as during the 2002 Chandra observations.
What could have caused Uranus to emit X-rays? Mostly the Sun. Astronomers have noticed that both Jupiter and Saturn scatter X-ray light emitted from the Sun, similar to the Earth’s atmosphere. While the authors of the new study initially expected most of the detected X-rays to be due to scattering, it is hoped that at least one other source of X-rays is present. If further observation confirms this, the concept of Uranus will change.
One possibility is that the rings of Uranus produce X-rays themselves, as is the case with the rings of Saturn. Uranus is surrounded by charged particles – electrons and protons – in nearby outer space. If these energetic particles collide with the rings, they can make them glow in X-rays. Another possibility is that at least some of the X-rays come from the auroras on Uranus. Previously, this phenomenon was observed at other wavelengths.