Venus and Earth provide astonishingly different views of the evolution of a rocky planet, raising the question of why these two rocky worlds evolved so differently. The recently discovered transiting super-Earth LP 890-9c is a key to the question. This exoplanet circles the nearby red dwarf star LP 890-9 in 8.46 days and receives a similar amount of energy as modern Earth receives from the Sun, which puts LP 890-9c very close to the inner edge of the habitable zone.
LP 890-9 is located approximately 104 light-years away from Earth in the constellation of Eridanus.
Otherwise known as TOI-4306 and SPECULOOS-2, the star has a mass of only 0.16 solar masses, a radius of 0.12 solar radii, and a temperature of 2,850 K (2,577 degrees Celsius, or 4,671 degrees Fahrenheit).
LP 890-9, which is orbited by at least two exoplanets, is the second-coolest star found to host planets after TRAPPIST-1.
The inner planet, LP 890-9b, is about 30% larger than Earth and completes an orbit around the star in just 2.73 days.
The outer planet, LP 890-9c, is similar in size to the first (about 37% larger than Earth) but has a longer orbital period of about 8.5 days.
“LP 890-9c is part of a two-planet system with the inner planet, LP 890-9b, first detected by TESS in a 2.73-day orbit, inward of the habitable zone,” said Cornell University astronomer Lisa Kaltenegger and her colleagues.
“However, LP 890-9c, receives 91% as much solar radiation as Earth, placing it within both the conservative and empirical habitable zone.”
“This makes LP 890-9c a key to understanding how Venus and Earth evolved.”
To explore the range of possible atmospheres and assess whether transmission spectra can illuminate that difference, the astronomers created seven models for LP890-9c.
“Looking at this planet will tell us what’s happening on this inner edge of the habitable zone — how long a rocky planet can maintain habitability when it starts to get hot,” Dr. Kaltenegger said.
“It will…
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