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It’s hard to believe that just four decades ago, we had no idea whether planets existed outside our solar system. Scientists discovered the first exoplanet in 1992, and since then our understanding of the universe has changed irrevocably. Now, scientists estimate that there are as many planets around us as there are stars. The cosmos are littered with icy, gaseous, and rocky bodies that may one day reveal life on another world.
As of October 24, 2023, scientists have confirmed the existence of 5,535 planets outside of our solar system. In some ways that discovery belongs to all of us because we are part of this universe. The hunt for exoplanets allows all of us to be scientists.
That’s certainly a nice sentiment, but when it comes to exoplanets, it’s actually true: Citizen scientists are working every day alongside those with PhDs to find the next exoplanet. One of the many people we have to thank for that is Dr. Jessie Christiansen, an astronomer at the California Institute of Technology.
In 2017 Dr. Christiansen, along with Dr. Ian Crossfield, was instrumental in ensuring that the planet-hunting data from Kepler’s K2 mission extension was made public. This ensured citizen scientists could become planet hunters.
As a project scientist on NASA’s Exoplanet Archive, she passionately continues this work, sharing science with the world and working tirelessly to ensure public access to scientific data. “We’re really having a cultural moment in science about data access,” says Dr. Christiansen. “One of the things the internet has done is make everybody realize there are data that should be available and accessible.”
How the NASA Exoplanet Archive Works
“This is how NASA keeps track of all the planets we’ve found around other stars,” Dr. Christiansen says. The Exoplanet Archive offers cataloging information and gives scientists (and anyone else with an interest) tools and data they can use to further study exoplanets. But it doesn’t happen all by itself. Dr. Christiansen is one member of a team of three scientists (along with two data analysts, a handful of software engineers, a system administrator, and a technical writer) at NASA’s Jet Propulsion Laboratory (which is managed by Caltech) who identify confirmed exoplanets for inclusion in NASA’s database.
So, how does one get a planet into the archive?
“You can’t just stand up at a conference and be like ‘We’ve found an exoplanet!’” she jokes. In order for an exoplanet to be admitted, it has to be included in an accepted, peer-reviewed paper. Once that happens, a team member will track down the paper (sometimes it’s emailed to them, but more often than not one of the three scientists will use online databases to find them—they rotate monthlong shifts).
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The work—combing through papers on arXiv.org and other services—can be mind numbing, but it’s worth it. “I get to have that moment where I'm looking at the data and I realize I’m the only person who knows right now that this star has a planet around it,” she says excitedly. That thrill of discovery excites her, but the thing that fuels her? It’s talking to people about science.
“I’m going to spend the next two hours looking at papers,” she says. “Science communication has never been part of my official duties, but it gives me life. I need this.”
Science Communication and Giving Back
Science communication has always been important to Dr. Christiansen. When she was at university in Australia, she knew she wanted to study science, but because she was the first in her family to go to college, she had no idea what the possibilities were. “Once I was at university in a science school and looking around, I realized, ‘Wait, there are people who are paid to just hang out and answer science questions?’” That’s when she decided to become an astronomer—because she wanted to talk to people about science. “I’m so lucky, I get to hunt for planets as my job,” Dr. Christiansen exclaims. “I want to know if there’s other life out there. I want to know if we’re alone. It’s one of the oldest questions we have—are we alone?”
It’s no secret that there are many people who think NASA is a waste of money.
Part of why Dr. Christiansen prioritizes science communication is that it’s a way she can give back. “I want to explain to people that we are good stewards of their money, and here’s the exciting things we’re doing with it.” Another motivation is to be a role model for young girls who want to become scientists.
That’s why she’s heavily involved in mentorship and is a TED fellow. And it’s why she advocates for public data—so anyone can become a scientist.
The Importance of Publicly Accessible Data
NASA’s Exoplanet Archive is incredibly important work that’s crucial for the exoplanet community, whether it’s astronomers working to find new exoplanets or citizen scientists combing through data sets. It’s the public accessibility of data (in a good format, with useful documentation) that’s crucial. “One of the main reasons I’m passionate about making sure data are accessible and open is it really democratizes science.” Getting science into the hands of ordinary people is very important to Dr. Christiansen.
“There’s a lot of science done by people in their ivory towers with their access to their great telescopes, and there’s no reason that data would ever become public,” she explains. “One of the reasons I love working for NASA is that’s not how NASA operates. It’s taxpayer funded. It’s your data, you pay for it.”
Citizen science has played a large role in the confirmation of exoplanets for a very good reason: the sheer breadth of data. It’s more than any single human can analyze. Of course scientists can write computer programs to analyze the data, but software doesn’t have a gut instinct, as Dr. Christiansen points out. It can’t look at a set of data and tell you where something is off, the way a human can.
Want to find your own exoplanet? You can do it easily with TESS data. TESS, or the Transiting Exoplanet Survey Satellite, is a spacecraft that monitors over 200,000 stars for dips in brightness. This is one of the simplest ways to find exoplanets–when a planet travels in front of its host star as seen from Earth, there’s a measurable dip in that star’s brightness. But TESS only identifies exoplanet candidates. These candidates have to be independently confirmed by humans.
PlanetHunters.org makes light curves from TESS available to the public. After a short tutorial, anyone with internet access can dive in and start looking for their own exoplanet.
“Almost all of the really unique planetary systems have been found by citizen scientists because they were able to look at the data,” says Dr. Christiansen. “Anyone can go on PlanetHunters.org and find their own planet. It’s just delightful. The number of citizen scientists I’ve been able to publish papers with who have found their own planet—it’s really cool.”
“And I get to enable that,” she says.
