Brown Dwarf Boasts Brightest Auroras Ever Seen [Slide Show]
Astronomers just spotted auroras on a brown dwarf for the first time, but this is just the latest case of known extraterrestrial auroras
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Brown Dwarf Boasts Brightest Auroras Ever Seen [Slide Show]
- EARTH Earth's magnetic field funnels particles carried in solar wind and huge solar eruptions called coronal mass ejections toward its north and south poles, producing the auroras borealis and australis (the northern and southern Lights, respectively). Charged particle collisions with atmospheric oxygen create red or yellowish-green hues whereas collisions with nitrogen paint the sky with blue illumination. As the International Space Station passed over the eastern North Atlantic Ocean in 2011, the crew snapped this shot of the aurora borealis shimmering above city lights in England and Ireland. Credit: NASA
- MARS The European Space Agency's Mars Express orbiter first detected auroras on the Red Planet in 2005. Unlike Earth, Mars no longer has a global magnetic field. But it did for a brief window of time more than four billion years ago. When molten magnetizable material from that era solidified, it locked up remnant fields. So Mars now has umbrella-shaped magnetic fields blooming out of the ground all over its surface, particularly in its southern hemisphere. Any one of these fields can snag charged particles from the solar wind and produce auroras. Spacecraft have only detected ultraviolet radiation from these auroras but recent lab experiments with an aurora simulator suggest that Martian auroras might also emit visible light. If so, future human colonists on the Red Planet might see something like the artist's rendering of Martian auroras shown above. Credit: NASA/JPL-CALTECH
- SATURN Charged solar wind particles collide with hydrogen atoms and molecules in Saturn's atmosphere, giving off ultraviolet light. We can only observe this auroral light show using telescopes and spacecraft. The picture above shows an ultraviolet image of Saturn's south pole taken with Hubble Space Telescope in 2004 (with ultraviolet radiation shown in blue) overlaid on a photo of Saturn in visible light. Unlike earthly auroras, which last for mere minutes, Saturn's auroras can glow for days. Credit: NASA, ESA, J. Clarke (Boston University), and Z. Levay (STScI)
- JUPITER Jupiter's ever-present auroras, powered by the solar wind, are thousands of times brighter than those on Earth. Additionally, Jupiter's interactions with one of its major moons, Io, occasionally cause the planet to flare with particularly luminous auroral storms. Io's volcanoes belch clouds of charged atoms and electrons into the space around Jupiter where they are caught in the planet's immense magnetic field and produce dazzling auroras that primarily consist of invisible ultraviolet and x-ray radiation. Until the discovery of auroral activity on LSR J1835+3259, Jupiter held the record for most powerful auroras. The Hubble Space Telescope took the above image in 2000. Credit: John Clarke, Denis Grodent, ESA, and NASA
- URANUS Here Hubble observations of Uranus's auroras in visible and ultraviolet light are superimposed on photos of the planetary disk taken by the Voyager 2 spacecraft during its 1986 flyby. Hubble snapped these pictures in November 2011, during a time of heightened solar activity when a torrent of solar wind particles set the planet alight with auroras. The placement of the auroras on the planetary disk might at first seem strange--they do not seem to be located anywhere near the planet's poles. But unlike the magnetic field threaded through Earth, Uranus' field tips almost 60 degrees relative to its spin axis, so its auroras do not align with the planet's north and south poles.
Credit: NASA, ESA, and L. Lamy (Observatory of Paris, CNRS, CNES) - BROWN DWARF A team of astronomers recently spotted aurora activity on a brown dwarf dubbed LSR J1835+3259. They observed the auroras using the Very Large Array of radio telescopes in New Mexico, and the Hale Telescope in California. Charged particles flare with radio emission as they travel along the brown dwarf's magnetic field lines toward its atmosphere, where they collide with hydrogen atoms that subsequently release flashes of red visible light. The auroras on LSR J1835+3259 are the brightest astronomers have ever seen. Because the brown dwarf does not orbit a star that can bombard it with solar wind, some other unidentified object, such as an orbiting planet, must provide the charged particles that power the brown dwarf's auroras. Credit: Chuck Carter and Gregg Hallinan, Caltech
