Join Donate

How Does Finds Exo-Earths Work

When planet hunters train their telescopes on the stars, they usually aren't looking for an actual visual image of any planets. The distances are simply too vast. Rather, they seek evidence of those distant planets based on the behavior of the light from the stars themselves.

The most common method is called the "radial velocity technique," which relies on measuring minute Doppler effect changes in the star's light. The starlight changes because orbiting planets "tug" on their stars; so, as they circle, a minute Doppler effect occurs in the starlight. This tug either pulls the light waves slightly apart, or pushes them slightly together, changing their frequency. (It's the same effect that occurs to sound waves when a train rushes by you, with the sound of its whistle suddenly dropping in pitch.)

You can imagine how small these changes are, and how hard to detect. Modern technologies make it possible, but there are limits. For example, the terrific 3-meter telescope at the Lick Observatory can detect Doppler velocities of about 5 meters per second. That's good enough to spot enormous Jupiter-sized planets.

But to identify smaller worlds -- the ones more likely to have life -- a telescope must be able to detect Doppler velocities of 1 meter per second. To detect a planet the size and density of Earth, the precision would have to be under 0.5 meters per second.

The Marcy-Fischer team has tackled this problem by devising not one, but two optical systems to be used in tandem. The first is a fiber optics array that makes the cone of light entering the telescope's spectrometer "uniform," and therefore resilient to naturally occurring changes that foul up Doppler measurements.

The second part is an adaptive optics system that keeps the maximum amount of light flowing through the system -- that is, providing a better "signal-to-noise ratio."

Altogether, this bundle of new technology is referred to as Fiber-optic Improved Next generation Doppler Search for Exo-Earths, or FINDS. At Lick, it improved detection to the 1-meter range, enabling additional discovery of many Neptune-sized planets and larger. Marcy-Fischer were able to do all that with our help, and now it's on to the Keck Telescope, where 0.5 meter precision (and Earth-size planet discoveries) can happen.

And, once our instrument is adapted for the Keck Telescope, FINDS Exo-Earths 2 will provide crucial follow-up for planets found by the Kepler mission. Specifically, the Keck Telescope -- equipped with FINDS 2 -- will rule out false positive detections of Earth-sized worlds.

We're on the brink of discovering Earth-like planets around other stars -- worlds that may support life. You can play a key role in the hunt!

Bill Nye and people
Let's Change the World

Become a member of The Planetary Society and together we will create the future of space exploration.

Join Today

The Planetary Fund

Help advance robotic and human space exploration, defend our planet, and search for life.


You are here: