Strange, hidden Jupiter-sized exoplanet spotted by astronomers and citizen scientists

A group of astronomers and citizen scientists have discovered a hidden planet the size of Jupiter in a distant solar system, and they should be lucky enough to see it again soon.

The planet, designated TOI-2180 b, is relatively close to us here on Earth, just 379 light-years away. But what makes this world special among the sample of known giant exoplanets is that it takes 261 days to orbit its host star, far longer than most gas giants discovered outside our solar neighborhood. .

The team spotted the world using data collected by NASA’s Transiting Exoplanet Survey Satellite, or TESS. TESS spots exoplanets by finding very small, repeatable dips in a star’s brightness that are caused by a planet blocking some of the star’s light as it transits or passes between the spacecraft and the star. While the orbital period of TOI-2180 b is not entirely confirmed, scientists predict that TESS will see the planet again in February.

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“Transit events … are the best way to discover cooler exoplanets,” study lead author Paul Dalba, a postdoctoral researcher at the University of California Riverside, told a news conference on the planet. discovered at the 239th meeting of the American Astronomical Society on Thursday (January 13).

Dalba described it as “cool” not only because of the uniqueness of the exoplanet, but also because of its lower temperature caused by its longer-period orbit around its parent star. (The presentation is available in the video below, starting at around 34 minutes.)

“There is a lot of scientific motivation,” added Dalba. “We can ask questions like ‘Do short and long orbiting exoplanets form or evolve differently? How do they change over time? “”

TOI-2180 is about the same size as Jupiter. But it’s almost three times as massive; the planet contains about 105 Earth masses of elements heavier than hydrogen and helium, according to a statement from the University of New Mexico, the home institution of discovery team member Diana Dragomir . This difference in density could indicate that the planet formed differently from Jupiter.

Another oddity is the planet’s temperature, which averages a surprisingly mild 170 degrees Fahrenheit (77 degrees Celsius). Although TOI-2180 b is hotter than Jupiter and Saturn, it is still quite cold compared to many other huge exoplanets. (Many of the gas giant exoplanets discovered to date are near-orbiting “hot Jupiters,” which are easier to find because they transit more often and exert a greater gravitational pull on their host stars than planets orbiting further out. )

“It’s a good stepping stone between most of the giant exoplanets we’ve found and then really cold Jupiter and Saturn,” Dalba said in a NASA press release. This temperature difference is not yet understood, but could be explored further with observations from other observatories, such as NASA’s just-launched James Webb Space Telescope, the investigators said.

This discovery was made by a unique team of astronomers and citizen scientists, including former US Navy officer Tom Jacobs. Jacobs participates in Planet Hunters, a NASA-funded citizen science project run through the online platform Zooniverse that focused on data from NASA’s now-retired Kepler planet-hunting spacecraft.

“The discovery and publication of TOI-2180 b was a great group effort demonstrating that professional astronomers and seasoned citizen scientists can work together successfully,” Jacobs said in the same NASA statement.

Together, the team of citizen scientists and astronomers examined the TESS data in a collaboration called the Visual Survey Group. Jacobs spotted a dip in brightness in the new planet’s parent star on February 1, 2020. Since fluctuations in stellar brightness may be due to other factors such as sunspots, Jacobs needed confirmation and alerted astronomers Dalba and Dragomir.

TESS saw only one fading of the star, but the team received more information through observations from the automated planet-finding telescope at Lick Observatory in California, as well as the observatory WM Keck in Hawaii. Both of these observatories saw the planet’s gravitational “tug” on its parent star, allowing the team to focus on its mass.

The orbit of the planet, however, remains uncertain. The team tried to figure it out by looking for a transit again using telescopes at 14 sites, on three continents, in August 2020.

While the collaboration produced 55 datasets in 11 days, no telescope captured the transit. But this lack of information still allowed astronomers to “put a limit” on its orbital time, which they estimate at 261 days, NASA said.

Scientists also hope to further study TOI-2180 b to search for rings or moons, which are common among gas giants in our own solar system. Most of the large exoplanets discovered have been found very close to their parent stars, where intense gravity can tear things like rings away from the planet. Since TOI-2810b is farther from its star, it may be a “fun system” in which to search for moons or rings, Dalba said in the NASA statement.

A study based on the research was published Thursday, January 13 in the Astronomical Journal.

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