Gigantic Planet Hides in Plain Sight

USING TYPICAL STARGAZING TOOLS, a UC Riverside astronomer and citizen scientists discovered a giant gas planet hidden from view. TOI-2180 b, with a diameter similar to Jupiter’s, is nearly 3x more massive than Jupiter and 105x the mass of Earth in elements heavier than helium and hydrogen. It is so far unique. The findings are published in the Astronomical Journal.

UCR astronomer Paul Dalba describes the planet as having a several-hundred-day orbit, is relatively close to Earth and is visible in transit in front of its star. It takes 261 days to complete a journey around its star.

Using the Lick Observatory’s Automated Planet Finder Telescope, Dalba and his colleagues observed the planet’s gravitational tug on the star, which allowed them to calculate the mass of TOI-2180 b. Over 11 days in August 2021, researchers gathered 20,000 images of the TOI-2180 star, though none detected the planet confidently.