Uranus was
identified as a planet in 1781 by astronomer
William Herschel, the first planet to be discovered in modern times. Herschel proposed naming the planet in honor of King George III, the "
mad king", and many other names were propsed for the planet, but the suggestion of
Uranus (the Greek god of the sky) by astronomer
Johann Bode was eventually adopted (ensuring the planet's place as the butt of mischievous schoolboy humor for centuries). Uranus is an unusual planet, a ringed
ice giant whose rotational axis lies nearly in the plane of the planet's orbit, making it appear as if the planet is rotating on its side. This weird orientation produces
extreme seasons and storms as the planet revolves in its 84 earth year orbit. Though poorly understood, ice giants like Uranus (and its cousin
Neptune) are fairly common in identified planetary systems outside the solar system. Now the
Chandra X-ray Observatory has shown, for the first time, that Uranus is a source of X-ray emission. The image above shows an X-ray image obtained by Chandra's
High Resolution Camera of the planet (in purple) superimposed on an optical image of Uranus from the
Keck observatory. The origin of this X-ray emission is not yet known. Likely much of the emission is produced by X-rays from the Sun being reflected by the planet's atmosphere, but emission from polar
aurorae or X-rays from the interaction of charged particles with ice in the rings of Uranus (a process that produces
X-ray emission from comets) might also contribute.
HEAPOW: Uranus X-rayed (2021 Apr 12)
