Discovery of Potentially Habitable Earth-Like Planet

 Astronomers discover a temperate exoplanet which could host life just next 35 Light-Years Away     

In the hunt for life beyond Earth, astronomers have zeroed in on L 98-59, a humble red dwarf just 35 light-years from us. Scientists have confirmed a potentially habitable fifth planet, revealing a diverse collection of rocky worlds which could harbour water or volcanic activity. A research team from the Trottier Institute for Research on Exoplanets (IREx) has completed the most detailed investigation yet of the planetary system surrounding L 98-59, a nearby red dwarf star. Their analysis confirmed a fifth planet located within the star’s habitable zone, an area where conditions may support the presence of liquid water. Once thought to host four rocky planets, new analysis reveals a fifth world sitting squarely in its star’s “sweet spot” for liquid water. This discovery turns L 98-59 into one of the most exciting, diverse and accessible systems for future exploration.

L 98-59 sits just 35 light-years from Earth and is orbited by three small exoplanets first spotted 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. These four planets travel extremely close to their star, each orbiting at a distance much shorter than Mercury’s path around the Sun. Led by Charles Cadieux of Université de Montréal and IREx, the team re-examined extensive data from both ground and space-based telescopes. This effort allowed them to measure the planets’ sizes and masses with a level of accuracy never achieved before. L 98-59, a small red dwarf in the southern sky. Despite its size, it hosts at least five rocky planets, and the latest discovery might be the most thrilling yet. Early surveys by NASA’s TESS and ESO’s ESPRESSO spotted four rocky worlds circling L 98-59. Now, astronomers have dug into existing data, using clever radial-velocity techniques and temperature-tracking methods, to pull out a fifth planet from the noise. Here is a comparison of the estimated sizes of the first three planets orbiting the red dwarf L 98-59. 

Meet Its Siblings:-                      Four Rocky Worlds

Sub-Earth:-                                Only 84 % of Earth’s width and half its mass.

Volcanic Neighbour:-                 About 1.33 R⊕, likely tidally heated, like Jupiter’s moon Io.

Ocean Candidate:-                     At 1.63 R⊕, its low density hints at a deep water layer.

Heavy Hitter:-                            Nearly three Earth masses, rounding out the inner foursome.

All orbit in near-perfect circles, making the system unusually tidy.

“These new results paint the most complete picture we’ve ever had of the fascinating L 98-59 system,” said Cadieux. “It’s a powerful demonstration of what we can achieve by combining data from space telescopes and high-precision instruments on Earth, and it gives us key targets for future atmospheric studies with the James Webb Space Telescope [JWST].” 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 real showstopper orbits in just 23 days, bathing in Earth-like starlight. This places it in L 98-59’s habitable zone, where liquid water could exist. “Finding a temperate planet in such a tight system is thrilling,” says Charles Cadieux of the Université de Montréal. “It shows how diverse exoplanet systems can be, and why low-mass stars deserve our focus.” They employed the novel line-by-line radial velocity analysis technique introduced by IREx researchers in 2022 to improve the precision of the data significantly. 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. 

The refined measurements reveal nearly perfectly circular orbits for the inner planets, a favourable configuration for future atmospheric detections. “With its diversity of rocky worlds and range of planetary compositions, L 98-59 offers a unique laboratory to address some of the field’s most pressing questions: What are super-Earths and sub-Neptunes made of? Do planets form differently around small stars? Can rocky planets around red dwarfs retain atmospheres over time?” adds René Doyon, co-author of the study, who is a professor at UdeM and the Director of IREx. One of the key breakthroughs of this study is the confirmation of a fifth planet in the L 98-59 system. This planet, designated L 98-59 f, does not transit its host star, meaning it doesn’t pass directly between us and the star, but its presence was revealed through subtle variations in the star’s motion. L 98-59 f receives about the same amount of stellar energy as Earth does from the Sun, placing it firmly within the temperate, or habitable zone, a region where water could remain in liquid form. L 98-59 is now a top target for the James Webb Space Telescope. These nearby, rocky planets let us probe atmospheres and, one day, maybe even signs of alien life. With its rich line up of worlds, this star system is a perfect laboratory for studying how planets, and potentially life, form around cool, dim stars. Rather than requesting new telescope time, 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.

These results confirm L 98-59 as one of the most compelling nearby systems for exploring the diversity of rocky planets, and, eventually, searching for signs of life. Its proximity, the small size of its star and the range of planetary compositions and orbits make it an ideal candidate for atmospheric follow-up with the JWST, which the IREx team has already started. “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.”