By Pat Brennan
A new project invites amateur astronomers and citizen scientists to help NASA track, and perhaps even discover, planets orbiting distant stars.
Scientists have discovered more than 4,400 exoplanets – planets that orbit other stars – over the past quarter century. A new project, called Exoplanet Watch, allows observers with a modest backyard telescope and camera to trace the tiny, faint shadows cast by these planets as they cross the faces of their stars.
In fact, they can take part even without a telescope. Using data-processing software provided by the program, they can use a home computer to help analyze observations from others.
Successful participants even will earn an author's credit on a published scientific paper.
"It's an opportunity to allow amateur astronomers, or students, to examine exoplanets in real time," said Tamim Fatahi, a junior and computer science major at the California Polytechnic State University in San Luis Obispo, hired for an internship on the Exoplanet Watch project. "You do not have to have [an advanced] degree."
Headed by the Universe of Learning team under NASA's Science Activation Program, the new program has a solid scientific purpose: to provide backup to professional exoplanet observing campaigns that use large telescopes on the ground and in space.
Searching for the shadows of exoplanets is known as the "transit" method: capturing the tiny dip in starlight as a planet passes in front of its star. Of the thousands of exoplanets confirmed in our galaxy so far, most have been found by watching for planetary "transits."
To confirm a planet’s existence, scientists typically want to observe such a transit more than once. Doing so can reveal properties of the planet – its diameter, for instance, or the length of its year (the time it takes to make one orbit around its star). It's these repeated transits that Exoplanet Watch seeks to nail down firmly.
But predicting the next transit of any given planet can be a difficult proposition. The timing of transits is poorly known for many potentially interesting targets.
"If there's a 15-minute under-estimate of when a transit will occur, that's an extra 15 minutes I have to build into my observing scenario," said Rob Zellem, an exoplanet astronomer at NASA's Jet Propulsion Laboratory and the project lead for Exoplanet Watch.
Fifteen minutes doesn't sound so bad – until you consider the outsized demand for observing time on instruments like the Hubble Space Telescope.
"Time on big telescopes, especially space telescopes, is very, very precious," Zellem said. "If you're observing a lot of planets, [15 minutes] could add up to a substantial amount of time. Any time wasted means less science will be done with that telescope."
Enter the citizen scientists.
Armed with a nothing more than a six-inch telescope and a digital camera attachment, you can join their ranks, hunting for planets and turning your own home into an observatory. The project will offer participants regular updates on stars for which more observations are needed, as well as likely transit times, which they can help refine. They’ll also receive user-friendly instructions on how to upload their data to its processing software.
These observations will save professional astronomers time and resources as they eventually turn their powerful instruments to those same planets.
"I really love the project, and I really love working with citizen scientists," said Marlee Smith, a senior at Columbia University and a double major in computer science and astronomy.
She also worked as an intern on the project, and her help, along with that of other interns, was essential to making Exoplanet Watch ready for prime time.
"We're extending science to people who wouldn't necessarily think to do science at first – science for everybody, anytime," she said.
Looking for light curves
Smith and the others spent much of their time improving the computer code, called EXOTIC (for Exoplanet Transit Interpretation Code), that allows homegrown observers to input their data; EXOTIC then converts it into "light curves," the bread and butter of exoplanet hunters.
As a planet begins to move across the face of a distant star, the corresponding light curve begins as a flat line. Then it takes a sharp dip as the planet moves toward the star's center and blocks a tiny percentage of the star's light.
As the planet moves past the star's face, the line rises again to its formerly flat position; the resulting wavy line is the planet's "light curve."
If the star's diameter is known, the depth of the dip reveals the diameter of the planet. The larger the planet, the more starlight it blocks. Wait for a second dip, as the planet comes back around, and you know the length of the planet's year – one trip around the star.
Another intern with the project, Aaron Tran, spent his summer working on the software that will process the data from amateur telescopes. A computer science major with an interest in astronomy, Tran says he was taken with one of the project's main goals: to make exoplanet astronomy accessible to everyone.
"Observing exoplanets with telescopes you buy off (the internet), instead of using one on a mountaintop, was one of the biggest draws for me," Tran said.
Making Exoplanet Watch accessible was a big draw as well for Tiana James, a sophomore at Howard University in Washington, D.C. Also hired as an intern, James, who studies computer information systems and graphic design, is helping to make the site "very beginner friendly."
And in the spirit of opening the site to everyone, she's developing a feature that would "sonify" the light-curve data.
"When you put in the data for a light curve, instead of being able to see it, it would emit a sound wave," she said. "You would be able to hear it. Then you would be able to say, 'Ok, this is where the light curve was.' For people with interest who are blind, this is a really great feature."
The Exoplanet Watch team is committed to making its science accessible to all, says Rachel Zimmerman-Brachman, a public engagement specialist at the Jet Propulsion Laboratory who is lending her expertise to the project.
“I’m raising awareness about the opportunity for people to participate in exoplanet studies as citizen scientists,” she said. That includes “making hands-on science – particularly exoplanet science – accessible to as many people as possible.”
Searching for planets with an ever-growing pool of budding astronomers, students, or anyone who might be curious: Exoplanet Watch is an invitation to explore the universe.
Want to explore other citizen science opportunities? Visit NASA's Citizen Science portal.
NASA’s Universe of Learning materials are based upon work supported by NASA under cooperative agreement award number NNX16AC65A to the Space Telescope Science Institute, working in partnership with Caltech/IPAC, Jet Propulsion Laboratory, Center for Astrophysics | Harvard & Smithsonian, and Sonoma State University. The award is part of NASA’s Science Activation program, which strives to further enable NASA science experts and content into the learning environment more effectively and efficiently with learners of all ages.