New fifth planet present in system of remarkably numerous worlds

• L 98-59 is a crimson dwarf star with a number of small planets orbiting it. It is just 35 light-years from Earth. Previously, astronomers knew of 4 planets within the system.
• Now, astronomers have found a fifth planet, within the liveable zone of the star. They discovered it by re-analyzing older knowledge from each floor and space-based telescopes.
• The planets of L 98-59 are remarkably numerous. The two closest to the star is perhaps extremely volcanic, like Jupiter’s moon Io. Meanwhile, the third and least dense planet is perhaps a water world.

A fifth planet for L 98-59

L 98-59 is an enchanting planetary system solely 35 light-years from Earth. Astronomers beforehand discovered 4 small exoplanets orbiting the crimson dwarf star. And now a analysis staff led by the Trottier Institute for Research on Exoplanets (IREx) on the University of Montreal in Canada has confirmed a fifth planet. The researchers said on July 22, 2025, that the planet – L 98-59 f – is orbiting within the star’s habitable zone, the place water might probably exist. In addition, the analysis staff has decided the sizes and much of all of the planets with unprecedented precision.

They used an archive of information from NASA’s TESS house telescope, the European Southern Observatory’s HARPS and ESPRESSO spectrographs in Chile, and NASA’s James Webb Space Telescope (JWST).

Previously, NASA’s TESS house telescope found the primary three planets in 2019, and the fourth planet was present in 2021. This is now the fifth identified planet orbiting L 98-59.

The researchers have submitted their new peer-reviewed paper to The Astronomical Journal. Meanwhile, a preprint version is at present accessible on arXiv, submitted on July 12, 2025.

fifth planet is within the liveable zone

The astronomers discovered the fifth planet – known as L 98-59 f – utilizing the radial velocity method. Basically, it’s when the gravity of a planet barely tugs on its host star because it orbits. Consequently, astronomers can then detect these very slight variations within the movement of the star. The staff used knowledge from the HARPS (High Accuracy Radial velocity Planet Searcher) spectrograph on the ESO 3.6-meter telescope and the ESPRESSO spectrograph on the Very Large Telescope (VLT), each in Chile.

Although this planet, just like the others, orbits near its star, it’s throughout the star’s liveable zone. This is the area the place temperatures might enable liquid water. This is feasible as a result of the star is smaller and cooler than our solar. Its liveable zone, due to this fact, is nearer to the star than our solar’s liveable zone. In truth, L 98-59 f receives about the identical quantity of stellar power as Earth does from the solar. Lead writer Charles Cadieux on the University of Montreal said:

Finding a temperate planet in such a compact system makes this discovery notably thrilling. It highlights the outstanding range of exoplanetary programs and strengthens the case for finding out probably liveable worlds round low-mass stars.

A various system of rocky worlds

The new discovery provides to the intrigue of this planetary system. Indeed, astronomers already knew the primary 4 planets had been a various and interesting assortment of worlds. Now, the brand new observations have helped the researchers decide their sizes and much with even better accuracy. Cadieux said:

These new outcomes paint essentially the most full image we’ve ever had of the fascinating L 98-59 system. It’s a strong demonstration of what we will obtain by combining knowledge from house telescopes and high-precision devices on Earth, and it offers us key targets for future atmospheric research with the James Webb Space Telescope.

At least 4 of the planets are rocky, like Earth. Scientists name these terrestrial planets. The third planet from the star, L 98-59 d, has a decrease density than the others, nevertheless. It is perhaps a water world, a rocky planet fully coated in water, or perhaps a planet composed principally of water with no strong floor. Previously, one other examine in 2024 prompt it is perhaps a volcanic world with a sulfur-rich environment.

In addition, the 2 closest planets to the star would possibly expertise vital volcanic exercise, attributable to tidal heating from the star. This is much like how Jupiter’s gravity heats the inside of its moon Io. Io is essentially the most volcanically energetic physique in our photo voltaic system. The closest planet to the star, L 98-59 b, is 84% the scale of Earth and solely half of Earth’s mass.

A novel pure laboratory

Co-author René Doyon, the director of the Trottier Institute for Research on Exoplanets on the University of Montreal, added:

With its range of rocky worlds and vary of planetary compositions, L 98-59 gives a novel laboratory to deal with among the subject’s most urgent questions: What are super-Earths and sub-Neptunes made from? Do planets type in another way round small stars? Can rocky planets round crimson dwarfs retain atmospheres over time?

Confirmation Of A Non-transiting Planet In The Habitable Zone Of The Nearby M dwarf L 98-59astrobiology.com/2025/07/conf… #astrobiology #exoplanet

— Astrobiology (@astrobiology.bsky.social) 2025-07-11T15:57:49.542Z

Improving outdated knowledge

Notably, the researchers didn’t discover the brand new planet by conducting new observations of L 98-59. Instead, they searched in older knowledge from NASA’s TESS house telescope, NASA’s James Webb Space Telescope and the HARPS spectrograph on the ESO 3.6-meter telescope and ESPRESSO spectrograph on the Very Large Telescope (VLT), each in Chile. They used an improved model of the radial velocity approach known as line-by-line (LBL). IREx researchers first developed the improved approach again in 2022.

The staff mixed LBL with an improved approach to measure a star’s temperature. This allowed them to take away extra stellar “noise” from the star to disclose the planet.

Also, the brand new evaluation of the info doubled the precision of the measurements of the sizes and much of all of the planets.

Co-author Étienne Artigau on the University of Montreal said:

We developed these strategies to unlock this sort of hidden potential in archival knowledge. It additionally highlights how enhancing evaluation instruments enable us to enhance upon earlier discoveries with knowledge which are simply ready to be revisited.

An thrilling planetary system

The researchers have additionally now began further observations of L 98-59 with the Webb house telescope. And really, it’s a fascinating planetary system of nice curiosity to astronomers. Co-author Alexandrine L’Heureux on the University of Montreal said:

With these new outcomes, L 98-59 joins the choose group of close by, compact planetary programs that we hope to know in better element over the approaching years. It’s thrilling to see it stand alongside programs like TRAPPIST-1 in our quest to unlock the character and formation of small planets orbiting crimson dwarf stars.

Bottom line: Astronomers have found a fifth planet within the L 98-59 planetary system, within the star’s liveable zone. The system incorporates a numerous vary of worlds.

Source (preprint): Detailed Architecture of the L 98-59 System and Confirmation of a Fifth Planet in the Habitable Zone

Via University of Montreal

Read extra: Is this a volcanic exoplanet? Hints are in its environment

Read extra: An interior photo voltaic system very like ours, 35 light-years away