Auroras Grace Stellar Skies
Stunning auroras play in Earth’s upper atmosphere, and similar cascading curtains grace the skies of giant planets, brown dwarfs — and even small stars.
Aurorae hover in ovals around Jupiter’s north and south poles. Jupiter serves as an analogy in a recent study by Jonathan Nichols and his colleagues as they study auroral displays on brown dwarfs and dwarf stars. NASA / ESA / J. Clarke
When Earth’s magnetic field tangles with that of the Sun, beautiful auroras ignite our night skies. Electrons and charged particles, driven by the solar wind, rain down on the Earth’s upper atmosphere, lighting up the polar regions in a dazzling, ethereal display. But auroral displays aren’t unique to Earth. They’ve also been observed on Jupiter and Saturn. And now, an international team of astronomers have announced their findings on auroras on other stars.
The group, led by Jonathan Nichols (University of Leicester), showed that ultra-cool dwarfs, objects much smaller and colder than the Sun, demonstrate auroral behavior similar to Jupiter and Saturn. Ultra-cool dwarf is a catch-all term for the runts of the star formation litter: low-mass stars and failed stars known as brown dwarfs are all roughly Jupiter-sized and emit just a few percent of the Sun’s luminosity.