The idea of having a world just like ours in a distant corner of this universe, in itself, feels mind boggling! The scientific community has been making significant strides in deciphering the mysteries of the possibility of life beyond our beloved settlement: the Earth. A recent discovery has fuelled the excitement!
L 98-59, also known as TOI-175, TIC 307210830, is an M dwarf about one-third the mass of the Sun. Located 35 light years from Earth, it is orbited by three small exoplanets and was first discovered in 2019 by NASA’s TESS space telescope. A fourth planet was later identified using radial velocity data collected by the European Southern Observatory’s ESPRESSO spectrograph. Lately, a research team from the Trottier Institute for Research on Exoplanets (IREx) has completed the most detailed investigation on the system. Their analysis has confirmed the existence of a fifth planet in the Goldilock’s zone (habitable zone), an area that is conducive for the presence of liquid water. Their results were an amalgamation of extensive data collected from space telescopes and high-precision instruments on Earth. All planets in the system have masses and sizes compatible with the terrestrial regime. The innermost planet, L 98-59 b, is only 84% of Earth’s size and about half its mass, making it one of the rare sub-Earths known with well-measured parameters.
The two inner planets may experience extreme volcanic activity due to tidal heating, similar to Jupiter’s volcanic Moon, Io, in the Solar System. Meanwhile, the third, unusually low in density, may be a “water world”, a planet enriched in water unlike anything in our Solar System. The team made these discoveries by relying on a rich archive of data from NASA’s TESS space telescope, ESO’s HARPS and ESPRESSO spectrographs in Chile, and the JWST in contrast to the conventional approach of requesting a new telescopic line.
The novel line-by-line radial velocity analysis technique introduced by IREx researchers in 2022 to improve the precision of the data significantly was employed. By combining it with a new differential temperature indicator also developed by the team, they were able to precisely identify and remove the stellar activity signal from the data, revealing the planetary signal in unprecedented detail.
By combining these enhanced measurements with analysis of transits seen by JWST, the team doubled the precision of mass and radius estimates for the known planets.“With these new results, L 98-59 joins the select group of nearby, compact planetary systems that we hope to understand in greater detail over the coming years,” says Alexandrine L’Heureux, co-author of the study and Ph.D. student at UdeM. “It’s exciting to see it stand alongside systems like TRAPPIST-1 in our quest to unlock the nature and formation of small planets orbiting red dwarf stars.”