Wednesday

There is no shortage of X-ray emitters in our Solar System. Out of all of them, one of the brightest sources is Jupiter thanks to its intense X-ray aurorae. Studies show that Jupiter’s powerful magnetic field accelerates ions primarily from the local environment into the planet’s atmosphere above the polar regions. The ions undergo charge stripping before they charge exchange with atmospheric neutrals and produce soft X-rays (photon energy 2 keV) arising from electron bremsstrahlung usually surrounds the soft X-ray emissions.

The Jovian system produces X-rays in a few other ways. For example, interactions between plasma in Jupiter’s magnetosphere and the Galilean Moons cause these satellites to fluoresce in X-rays. Jupiter’s atmosphere also scatters solar X-rays, something that is observed at Saturn as well. In addition to this, X-ray emissions from Saturn’s rings have been detected and are due to fluorescent scattering of solar X-rays from oxygen atoms in the icy rings. Several attempts to detect X-ray auroral emissions from Saturn have so far yielded no positive results.

Uranus has recently been added to the list of known X-ray emitters in the Solar System. Observations taken by the Chandra X-ray Observatory in 2002 and 2017 revealed a low signal detection of X-rays from the Ice Giant planet. The measured X-ray fluxes from these observations surpassed what was expected if the emissions were only from scattered solar X-rays. This suggests that Uranus may have a higher X-ray albedo than the Gas Giant planets, or that Uranus has at least one other process of producing X-rays.