The colors of life--in space

On Earth, researchers use fine differences in light and color to identify specific plant species in aerial photos, and even to distinguish diseased or stressed plants from healthy ones.

What if we could use a similar technique to identify life on other planets?

A team of University of Hawai`i scientists is proposing just that, and is targeting our nearest solar neighbor, Alpha Centauri—a binary star that is the third brightest star in the night sky. Its alternative names are Rigil Kent and Toliman.

The team is led by Dr. Svetlana Berdyugina, a visiting scientist at the University of  Hawai`i’s NASA Astrobiology Institute, working with Hawai`i astronomers Jeff Kuhn, David Harrington and John Messersmith.

They propose to use existing telescopes that are outfitted with special polarization equipment, and to compare the light from space with the colors from Earth-based photosynthetic pigments. Reflected polarized light from a planet can be picked up even when a nearby star is overwhelmingly brighter.

In their research, the team “found that each biopigment has its own colored footprint in such polarized light,” they said in a pressrelease.

They seem to admit that chances seem slim. A single planet was discovered last year around one of Alpha Centauri’s three stars, Alpha Centauri B. But this planet is far closer to its sun than even baked Mercury is to our sun, and so hot that water probably can’t exist at the surface. 

But using the powerful polarized photosynthetic signatures might identify other planets in what astronomers call the habitable zone—that area where liquid water can exist on the surface. The team believes that within the star cluster, Alpha Centauri B holds the best chance of having  planets in the habitable zone.

© Jan TenBruggencate 2015