For the first time, astronomers have spotted an aurora, akin
to our northern and southern lights, shimmering on a world
outside our solar system. The find may bolster the search for
extraterrestrial life, since the magnetic fields that drive auroras likely
keep planets habitable.
Every planet in our solar system (and even some moons) with a
moderate magnetic field boasts these celestial light shows. They
occur when charged space particles, typically from the sun, stream
along a planet’s magnetic field lines and interact with atmospheric
atoms, producing not only optical light but also radio emissions.
Gregg Hallinan of the California Institute of Technology and
colleagues have detected both types of radiation from what appears
to be a brown dwarf, an object that straddles the boundary between
planet and star. The world’s aurora, reported in Nature in July as about
a million times brighter than Earth’s, suggests that brown dwarfs have
magnetic activity more like planets than stars. Hallinan hopes more
observations shed light on the origins of the charged particles that
power the aurora, which are currently unknown.
The brown dwarf in question, called LSR J1835+3259, lies 18
light-years away, suggesting astronomers may soon glimpse auroras
on similarly distant planets, too. That could help narrow the search
for habitable planets, since the auroras reveal the strength of their
planets’ magnetic fields, which can shield against harmful stellar
radiation and help retain life-friendly conditions.
[This article originally appeared in print as "Alien Aurora."]