How to Detect Watery Worlds Around Other Stars

If you want to know what a watery world might look like orbiting another star, just observe our own planet… from afar. The Blue Marble image of Earth, taken by the Apollo 17 astronauts on December 1972, shows how our planet is 70% water. Another world like ours, orbiting a distant star should be obvious – assuming you have a much more powerful telescope, and use the right techniques to analyze the light bouncing off the watery world.

Researchers from Penn State and the University of Hawaii have developed a technique that they think will help identify these watery worlds; potential homes for life around other stars. This technique is detailed in the most recent edition of the journal Icarus.

“We are looking for Earth-like planets in the habitable zone of their star, a band not too hot nor too cold for life to exist,” says Darren M. Williams, associate professor of physics and astronomy, Penn State Erie. “We also want to know if there is water on these planets.”

Here’s how you might tell the difference between a hellish planet like Venus, and a more comfortable watery world like Earth. A planet like Venus has a very dense atmosphere that scatters sunlight in all directions. From our vantage point, we would see the amount of light coming from the planet change depending on its position to its parent star. Just like Venus, we would see this extrasolar planet go through phases, changing in brightness in a very predictable way.

A watery world, like the Earth, would actually appear much darker when the whole disk is illuminated, since water is darker than dirt. But when the planet is in crescent, sunlight would glance off the surface of the water, and it would actually appear brighter.

The astronomers want to monitor the light curve of a distant planet as it spins on its axis and orbits its star. By watching the brightness of the light coming from the planet, they should be able to determine if it has a dense Venusian atmosphere, or is a better match for a watery world.

The equipment isn’t ready yet, but in the next 10 to 20 years, an observatory will probably be built with enough sensitivity to collect light from Earth-sized planets orbiting other stars. And this method should help determine if they’ll watery worlds, capable of supporting life.

Original Source: Penn State News Release