Two Giant Exoplanets Found around Sun-Like Star


Professional astronomers and citizen scientists from the NASA-funded Planet Hunters TESS project have discovered a two-planet system around the bright Sun-like star HD 152843.

HD 152843 is a G-dwarf star located about 352 light-years away in the northern constellation of Hercules.

Otherwise known as TOI-2319 or SAO 84691, the star is about the same mass as the Sun, but almost 1.5 times bigger and slightly brighter.

The inner planet in the HD 152843 system is about 3.4 times bigger than Earth and 11.6 times as massive. Named HD 152843b, it completes an orbit around its star in about 12 days.

The outer planet is about 5.8 times bigger than Earth and 27.5 times more massive, making it a sub-Saturn. Named HD 152843c, it has an orbital period of between 19 and 35 days.

An artist’s rendering of the HD 152843 planetary system. Image credit: NASA / Scott Wiessinger.

“Studying them together, both of them at the same time, is really interesting to constrain theories of how planets both form and evolve over time,” said Nora Eisner, a doctoral student at the University of Oxford.

Three transit events from HD 152843b and c were detected by citizen scientists in the data from NASA’s Transiting Exoplanet Survey Satellite (TESS), as part of the Planet Hunters TESS project.

Then, professional astronomers took a closer look. By comparing the data to their models, they estimated that two transits came from the inner planet and the other came from a second, outer planet.

To make sure the transit signals came from planets and not other sources, the researchers needed to look at the star with a different method.

They used the HARPS-N instrument at the Telescopio Nazionale Galileo and the EXPRES instrument at Lowell Observatory to confirm the planetary nature of transiting signals.

“The HD 152843 planets are far too hot and gaseous to support life as we know it, but they are valuable to study as scientists learn about the range of possible planets in our Galaxy,” Eisner said.

“We’re taking baby steps towards the direction of finding an Earth-like planet and studying its atmosphere, and continue to push the boundaries of what we can see.”

The team’s paper was published in the Monthly Notices of the Royal Astronomical Society.

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