Exoplanet Aurorae 1,000 Times Brighter Than on Earth

By Mimi Nguyen Ly
July 22, 2011

Aurorae on planets outside our solar system, or exoplanets, could be 100 to 1,000 times brighter than those on Earth, according to new research, and this could also affect their habitability.

On Earth, these magnificent green and red lights flicker across the North and South polar skies when particles from the sun are attracted to the Earth’s magnetic field, and strike our atmosphere, causing air molecules to glow.

On exoplanets, the display is even more spectacular because the lights travel across the planet’s entire surface due to their closer proximity to the stars they orbit.

"I’d love to get a reservation on a tour to see these aurorae!" said lead author Ofer Cohen at the Harvard-Smithsonian Center for Astrophysics (CfA).

Strong aurorae can occur due to Coronal Mass Ejections (CME) when large amounts of plasma erupt from the sun’s surface into space. CMEs can cause geomagnetic storms on Earth, interfering with power grids and satellite-based systems like telecommunications.

"The impact to the exoplanet would be completely different than what we see in our solar system, and much more violent," said co-author Vinay Kashyap at CfA in the release.

Many exoplanets are gas giants like Jupiter, and hence dubbed "hot-Jupiters." They are orbiting their stars up to one hundred times closer than Earth’s orbit of the sun.

So what would happen to an exoplanet when its host star emits a CME?

In the computer model, a CME hits the "hot-Jupiter," weakening its magnetic shield, and creating aurorae around the equator up to 1,000 times stronger than on Earth. Yet the exoplanet is shielded from the nearby star’s huge forces.

"Our calculations show how well the planet’s protective mechanism works," Cohen said. "Even a planet with a magnetic field much weaker than Jupiter would stay relatively safe."

To be in the habitable zone, exoplanets associated with red dwarf stars, our galaxy’s most common stars, must be in a close orbit for water to be liquid as red dwarfs are cooler than the sun.

However, this means they would be subject to more violent CMEs, making them potentially less habitable.

The new research was published in the Astrophysical Journal on July 7.

Source: The Epoch Times.
Link: http://www.theepochtimes.com/n2/science/exoplanet-aurorae-1000-times-brighter-than-on-earth-59434.html.