Buzz Blog

Planet Hunter calls to Crowdsource the Universe.

Tuesday, October 02, 2012
Nothing puts a skip in your brisk autumnal step like the the announcement of the 2012 MacArthur 'genius' Fellows, which provides an inspiring and concise account of twenty-three veritably brilliant individuals working on daring and creative projects from filmmaking to neurobiology to instrument bow-making.

In the excitement of the moment, I'd like to highlight one of this year's MacArthur Fellows, Olivier Guyon, an astronomer and optical physicist who has proposed a cool investment of some of his no-strings-attached MacArthur grant: crowdsourcing the planet hunt.

Olivier Guyon-- Planet Hunter.
Image courtesy of The John D. & Catherine T. MacArthur Foundation.
One of the prime methods of detecting new planets is to lie in wait, watching the stars in the sky. "If we wait long enough," Guyon says, "a planet will pass in front of its star and the light we collect from the star will dim." Since planets are in orbit, this dimming will be a periodic, repeated signal.  The dimming caused by a planet eclipsing its star is a strong enough signal that amateur astronomers can actually detect it without special equipment.  The challenge, Guyon explains, is that there are a huge number of stars to monitor.

Here's Guyon's big idea: encourage everyone with a love of exploration and the night's sky to participate in tracking stars, collecting data, and sharing it in an open-source database. "This is one of the projects I'm looking forward to working on with this fellowship," Guyon says. "By starting a network of astronomers, amateur astronomers, schools, and the broader public to collect and make all this data available, people can participate in science – it's easier than they think.  Curiosity is the driving force behind all of this." He's done his research too. Using just a Cannon DSLR camera and the right software, Guyon says you can take images of the night's sky and recover the brightness of many stars simultaneously.  Using a commercial camera, anyone can be a planet hunter, detecting the eclipse of a planet crossing its star.

If you're interested in getting your astronomer skills up to snuff in the meantime, check out Discovery News's Top iPhone Apps for the Amateur Astronomer.

But the biggest crowdsourcing experiment aside, Guyon's already brought serious advances to astronomy. Olivier Guyon spends his days designing telescopes to hunt terrestrial exoplanets – earth-like planets that orbit around bright stars, like our Sun, but are located outside our solar system.

One of Guyon's major contributions to the study of terrestrial exoplanets was his design of a new telescope sensitive enough to image and characterize features of exoplanets, such as the planet's distance from its star and the size of the planet. The size and location of the planet relative to its star determines whether it could sustain life, says Guyon.  "There is a habitable zone around each star," he says, "where if you put a planet like the earth, you could sustain life similar to that on earth." In our solar system, the Earth is within the habitable zone, while Venus is a little too close and Mars is a little too far away.  Similarly, the size of the planet can determine whether or not it might have a habitable atmosphere. According to Guyon, astronomers are looking for planets they call "rocky planets" that are no smaller than Mars and no larger than twice the diameter of Earth. On planets smaller than Mars, gravity won't be strong enough to retain the atmosphere necessary for life, while on planets much much larger than Earth, the atmosphere becomes much too thick. 

Capturing direct images of exoplanets (rather than studying the change in light from its star) is a feat of optical acrobatics. The trick of the trade is to block the very bright light radiating from star in order to capture images of the smaller, dimmer planets. Guyon's telescope is a big advancement from traditional telescopes because it makes use of all of the light the telescope can collect from the distant light source.

Airy Pattern
Image from arXiv:astro-ph/0412179
When astronomers use a normal telescope to image a star, the incoming light produces a bulls-eye diffraction pattern called an Airy pattern. The bright side rings of the bulls eye obscures the much dimmer light coming from the planets that astronomers are trying to detect. In a telescope, these characteristic Airy diffraction rings come from the interference pattern produced by the light from the edges of the incoming beam.

Guyon's Optics: Guyon, O. Astronomy & Astrophysics 404, 379-387 (2003)



 Guyon reasoned that if he could concentrate the light towards the center of the beam and lower the intensity at the edge of the beam, the side rings would also be dampened.

"We use two lenses and mirrors of very weird shapes to change where the intensity of the light is centered," Guyon explains, "and inside the telescope, this optical set up transforms the intensity of the beam from what we have normally-- a beam with a sharp edge and high contrast – to a smooth-edged beam that doesn't produce diffraction rings."

By utilizing the full intensity and resolution of the incoming light, Guyon's method--Phase-Induced Amplitude Apodization (PIAA)-- enables astronomers to study characteristics of the planet and its potential as a home for life across the universe.


--- --- --- --- --- ---
For more, watch out for tweets by 'Twain
Posted by Quark Twain