Proxima b exoplanet might appear green

Auroras caused by powerful stellar flares could potentially be seen from Earth.
By Laurel Kornfeld | Oct 10, 2017
The planet orbiting Proxima Centauri, the star closest to our Sun, might appear greenish to observers if it has an Earth-like atmosphere.

That color would be the product of interaction between oxygen in its atmosphere and particles released by stellar activity.

Located 4.2 light years away, Proxima Centauri is an active star that undergoes more frequent stellar flares than our Sun.

It is also significantly smaller than the Sun, meaning its habitable zone is a region much closer to the star than the habitable zone of our solar system.

Approximately 20 times closer to Proxima Centauri than Earth is to our Sun, the planet, which has 1.3 Earth masses and is believed to be rocky, takes just 11.2 Earth days to complete a single orbit.

Exposed to more powerful and more frequent flares than Earth experiences, Proxima b could be subject to radiation levels that render it unable to support life.

The flares would also cause brilliant auroras on Proxima b if the planet has a magnetic field that can catch their charged particles and send them toward the planet's poles.

If Proxima b's atmosphere contains oxygen, these auroras, which would be 100 times more powerful than those on Earth, would appear green, according to a study led by Rodrigo Luger of the University of Washington and published in the journal Earth and Planetary Astrophysics.

These auroras would be so bright that observers on Earth using powerful telescopes would be capable of seeing them.

If scientists can successfully observe the auroras, they will be able to identify the components of the planet's atmosphere.

One of the auroras' effects would be that the planet would look like a "pale green dot" as opposed to the "pale blue dot," a term Carl Sagan used to describe Earth from a great distance.

The various colors of Earth's northern and southern auroras are produced by collisions between charged particles released in solar flares and various molecules in its atmosphere.

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