PhD student team involved in planet discovery

Discovery of planet Gliese 12 b may help unlock some aspects of our own solar system’s evolution.

Using observations by NASA’s TESS (Transiting Exoplanet Survey Satellite) and many other facilities, two teams of astronomers, including one co-led by an Edinburgh PhD student, have discovered a planet between the sizes of Earth and Venus only 40 light-years away.

Planet and host star

TESS stares at a large swath of the sky for about a month at a time, tracking the brightness changes of tens of thousands of stars at intervals ranging from 20 seconds to 30 minutes. Capturing transits — brief, regular dimmings of stars caused by the passage of orbiting worlds — is one of the mission’s primary goals.

The planet’s host star, called Gliese 12, is a cool red dwarf located almost 40 light-years away in the constellation Pisces. The star is only about 27% of the Sun’s size, with about 60% of the Sun’s surface temperature.

The newly discovered world, named Gliese 12 b, orbits every 12.8 days and is Earth’s size or slightly smaller — comparable to Venus. Assuming it has no atmosphere, the planet has a surface temperature estimated at around 107 degrees Fahrenheit (42 degrees Celsius).

International discovery

Two international teams are involved in the study, including one co-led by Larissa Palethorpe, a PhD student at the University of Edinburgh and University College London, and Shishir Dholakia, a PhD student based at the University of Southern Queensland.

Larissa Palethorpe explains:

It is thought that Earth’s and Venus’s first atmospheres were stripped away and then replenished by volcanic outgassing and bombardments from residual material in the solar system. The Earth is habitable, but Venus is not due to its complete loss of water. Because Gliese 12 b is between Earth and Venus in temperature, its atmosphere could teach us a lot about the habitability pathways planets take as they develop.

A paper led by the team which includes Masayuki Kuzuhara, a project assistant professor at the Astrobiology Center in Tokyo and Akihiko Fukui, a project assistant professor at the University of Tokyo, was published 23 May 2024 in The Astrophysical Journal Letters. The findings from Larissa Palethorpe and Shishir Dholakia were published in Monthly Notices of the Royal Astronomical Society on the same day.

Further studies

Both teams suggest that studying Gliese 12 b may help unlock some aspects of our own solar system’s evolution. Follow-up observations with NASA’s James Webb Space Telescope could help determine just how much atmosphere the planet retains as well as its composition.