Astronomers discovered gigantic planet hidden in plain sight

The gas giant is much closer to Earth than others like it.


UC Riverside astronomer and a group of eagle-eyed citizen scientists have recently discovered a giant gas planet, TOI-2180 b. They found the planet is a bright, slightly evolved G5 star, hidden in plain sight.

The planet is relatively close to Earth (379 lightyears) and has a several-hundred-day orbit. It has the same diameter as Jupiter but is three times more massive. According to scientists, it contains 105 times the mass of Earth in elements heavier than helium and hydrogen. Nothing quite like it exists in our solar system.

TOI-2180 b orbits its star in 261 days.

UCR astronomer Paul Dalba, who helped confirm the planet’s existence, said, “It journey around its star is a long time compared to many known gas giants outside our solar system. Its relative proximity to Earth and the brightness of the star it orbits also make it likely astronomers will be able to learn more about it.”

“The rule of thumb is that we need to see three ‘dips’ or transits before we believe we’ve found a planet. A telescope could cause a single transit event with a jitter or a star masquerading as a planet. For these reasons, TESS isn’t focused on these single transit events. However, a small group of citizen scientists is.”

While analyzing the TESS data, the scientists observed light from the TOI-2180 star just once. They then alerted Dalba, who specializes in studying planets that take long to orbit their stars.

Dalba and his colleagues used the Lick Observatory’s Automated Planet Finder Telescope to look for the planet’s gravitational tug on the star. This allowed them to estimate the mass of TOI-2180 b and a range of possibilities for its orbit.

Dalba said, “The effort they put in is significant and impressive because it’s hard to write code that can identify single transit events reliably. This is one area where humans are still beating code.”

Journal Reference:

  1. Paul A. Dalba et al. The TESS-Keck Survey. VIII. Confirmation of a Transiting Giant Planet on an Eccentric 261 Day Orbit with the Automated Planet Finder Telescope*. DOI: 10.3847/1538-3881/ac415b


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