Last year, a group of keen-eyed citizen scientists discovered a Jupiter-sized exoplanet lurking in plain sight. It’s slightly warmer than room temperature on Earth, floats 379 light-years away from us, and completes an orbit around a star with a mass similar to our sun every 261 days.
The foreign gas giant, called TOI-2180 b, had been hidden in NASA’s Transiting Exoplanet Survey Satellite, or TESS, data until now. Even the agency’s most incredible algorithms couldn’t detect it because it was so deeply interwoven.
In a statement, Paul Dalba, an astronomer at the University of California at Riverside and primary author of a paper on the discovery published January 13 in the Astronomical Journal, stated, “This is one area where humans are still beating code.” Instead of relying on automation, citizen scientists turned to a more accessible tool: their own eyes, along with hard labor.
Tom Jacobs, a retired US military officer and part of the citizen team, said he and his fellow amateur astronomers “dedicate several hours each day scanning the data out of pure delight and enthusiasm in progressing science.” They’ve co-authored 68 peer-reviewed research publications so far.
“We enjoy helping science,” Jacobs remarked. “I also enjoy this form of surveying because it gives me the feeling of being in a new, uncharted country that people have never visited.”
Humans vs. software
Professional exoplanet searchers typically use computers to filter through TESS’ mountains of data and examine brightness trends around neighboring stars. When a star dims from Earth’s perspective, it means that a planet in the star’s system is obstructing stellar rays of light heading our way.
Consider it a kind of cosmic Morse code by which exoplanets — and, more lately, exomoons – communicate with human astronomers.
However, although over 4,000 exoplanets have been discovered thanks to similar research, the tried-and-true method is up against a stumbling block. Remember that the TESS-scouring code tracks brightness trends, taking several datasets to discover an exoplanet. However, the newly discovered exoplanet displayed a “single-transit event.” As a result, it only came into contact with starlight once, providing only a single piece of information.
Jacobs and his fellow amateur scientists use downloadable software called LcTools to evaluate star luminosity in the form of light curves, or brightness adjustments over time, in TESS data. Jacobs first noticed TOI-2180 b’s signal on February 1, 2020, thanks to this level of investigation. The group’s name is aptly named the Visual Survey Group.
“The manual labor they put in is precious and outstanding,” Dalba added. “Because writing code that can run through a million light curves and correctly detect single-transit events is difficult.”
However, just as professional algorithms run against roadblocks, so does the human eye. There’s a reason why TESS codes look for many instances of star dimming. The possibility of detecting an actual exoplanet increase as the number of signals increases. Single-transit events, for example, may easily be dismissed as random data noise.
That’s why Dalba came in later to support Jacobs and his team’s breakthrough.
Dalba measured the star’s “wobble” to establish the exoplanet’s size and spent 500 days and 27 hours observing its orbit using the Automated Planet Finder Telescope at Lick Observatory in Mt. Hamilton, California.
The entire research team also planned an “observing campaign,” encouraging professional and amateur astronomers to set up telescopes at 14 locations across three continents to keep an eye on TOI-2180 b. They took almost 20,000 distinct photographs of the exoplanet’s star with varying degrees of brightness for 11 days.
Dalba spent five nights camping in Joshua Tree National Park in California to study the enormous exoplanet. “Discovering and publishing TOI-2180 b was a fantastic team effort that demonstrated how professional astronomers and seasoned citizen scientists can collaborate successfully,” Jacobs added. “It’s the epitome of synergy.”
Despite their efforts, Dalba, Jacobs, and the other astronomers claim they are still unsure about the condition of TOI-2180 b. Nonetheless, they discovered that the planet will transit its host star once more in February, opening them a new window for additional research.
NASA claims that the James Webb Space Telescope, which launched on Christmas Day, will be able to examine the unique exoplanet candidate in unprecedented detail in the future.