Sat. May 28th, 2022

Illustration of a gas giant exoplanet orbiting a G-type star

A gas giant exoplanet orbiting a G-type star similar to TOI-2180 b.


Last year, a crew of sharp-eyed civilian scientists discovered an exoplanet the size of Jupiter hidden in common sight. It is slightly warmer than room temperature on Earth, flowing 379 light-years from us and completing every 261st day orbiting a star with about the same mass as our sun.

Until now, the foreign gas giant, dubbed TOI-2180 b, was hidden in data collected by NASA’s Transiting Exoplanet Survey Satellite or TESS. It was so intertwined that even the agency’s best algorithms did not capture it.

“This is an area where humans are still coding,” said Paul Dalba, an astronomer at the University of California at Riverside and lead author of a study on the find, published Jan. 13 in the Astronomical Journal, in a statement. Instead of relying on automation, citizen researchers looked at a more accessible tool: their own eyes combined with hard work.

Tom Jacobs, a member of the civilian team and a former U.S. Navy officer, said he and other amateur astronomers “spend many hours each day examining the data out of sheer joy and interest in advancing science.” So far, they have co-authored over 68 peer-reviewed scientific articles.

“We love contributing to science,” Jacobs said. “And I love this type of survey, knowing that one is in a new, undiscovered territory that no human has seen before.”

Illustration of the exoplanet TOI-2180 b

An illustration of TOI-2180 b.

NASA / JPL-Caltech / R. Hurt

People against code

Typically, professional exoplanet hunters program computers to search TESS ‘piles of information and analyze brightness patterns around nearby stars. When a star is dimmed from Earth’s point of view, the change in brightness indicates that a planet in the star’s system is blocking star rays on its way to us.

Think of it as a kind of cosmic Morse code through which exoplanets – and more recently exomooners – signal their existence to human astronomers.

But while over 4,000 exoplanets owe their recognition to such an analysis, the tried and tested method faces a small obstacle. Remember, TESS scrub code tracks brightness patterns, which means that it requires several data sets to mark a possible exoplanet detection. However, the newly uncovered exoplanet exhibited what is called a “single-transit event.” It only crossed paths with starlight once, and therefore offers a single piece of data.

Using downloadable software called LcTools, Jacobs and other amateur researchers personally review TESS data to examine star brightness in the form of light curves or brightness adjustments over time. This level of scrutiny helped Jacobs first notice the TOI-2180 b signal on February 1, 2020. Appropriately, the group calls itself the Visual Survey Group.

“The manual effort they put in is really important and really impressive,” Dalba said. “Because it’s actually difficult to write code that can go through a million light curves and identify single transit events reliably.”

But just as expert algorithms hit obstacles, so does the human eye. TESS codes generally search for multiple instances of star attenuation for a reason. Multiple signals increase the likelihood of true exoplanet detection. Single-transit events, for example, could easily be chalked up to random noise in the data.

Therefore, Dalba later stepped in to strengthen the breakthrough from Jacobs and team.

Using the Automated Planet Finder Telescope at the Lick Observatory in Mt. Hamilton, California, measured Dalba’s “wobble” to determine the size of the exoplanet and spent 500 days and 27 hours observing its orbit.

Lick Observatory's Automated Planet Finder

Lick Observatory’s Automated Planet Finder, is used to help calculate the mass and orbit of the new planet.

Laurie Hatch / Lick Observatory

The entire research team also organized an “observation campaign” inviting both professional and non-professional astronomers to establish themselves in 14 locations across three continents using telescopes to monitor the TOI-2180 b. In total, over 11 days , they captured more than 20,000 separate images of the exoplanet’s star with varying degrees of brightness.

Dalba even camped for five nights in California’s Joshua Tree National Park to explore the massive exoplanet. “Discovering and publishing the TOI-2180b was a major team effort that demonstrated that professional astronomers and experienced civic scientists can work together successfully,” Jacobs said. “It’s synergy at its best.”

Despite the strenuous efforts, Dalba, Jacobs and the rest of the astronomers say they still lack confidence in confirming the status of the TOI-2180 b. Still, they discovered that the planet will transit its host star again in February, providing a new window for further analysis.

In the future, NASA says, the James Webb Space Telescope, which was launched on Christmas morning, could potentially study the new exoplanet candidate in unprecedented detail.

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