Professional astronomers and citizen scientists from the NASA-funded Planet Hunters TESS project have discovered a two-planet system around a bright star such as the Sun HD 152843.
HD 152843 is a G dwarf star located about 352 light-years away in the northern constellation Hercules.
Otherwise known as TOI-2319 or SAO 84691, this star has almost the same mass as the Sun, but is almost 1.5 times bigger and slightly brighter.
The inner planet in the HD 152843 system is about 3.4 times larger than Earth and 11.6 times larger. Named HD 152843b, it completes an orbit around its star in about 12 days.
This outer planet is about 5.8 times larger than Earth and 27.5 times more massive, making it sub-Saturn. Named HD 152843c, it has an orbital period of between 19 and 35 days.
“Studying them together, both at the same time, is very interesting for limiting theories about how planets form and evolve over time,” said Nora Eisner, a doctoral student at Oxford University.
Three transit events of HD 152843b and c were detected by citizen scientists in 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 with their model, they estimated that two of the transits came from the inner planet and the other from the second outer planet.
To make sure the transit signal came from the planet and not from another source, the researchers needed to look at the star using a different method.
They used the HARPS-N instrument at the Telescopio Nazionale Galileo and the EXPRES instrument at the Lowell Observatory to confirm the planetary nature of the transit signal.
“The HD 152843 planets are too hot and gassy 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,” said Eisner.
“We are taking small steps toward finding Earth-like planets and studying their atmospheres, and continue to push the boundaries of what we can see.”
Team paper published in Monthly Notices of the Royal Astronomical Society.
NL Eisner et al. 2021. Planet Hunter TESS III: two planets transiting around the bright G dwarf HD 152843. MNRA 505(2): 1827-1840; doi:10.1093/mnras/stab1253