About 34.6 light-years from Earth — a light-year is the distance light travels in one whole year — sits a small, cool star with a busy family of planets around it. That family has at least five members, and one of them, L 98-59 d, has been measured well enough to give scientists some useful clues. This system is close enough to study carefully, and far enough out to remind us how wide the universe really is.
The Star at the Center
The star is called L 98-59. It belongs to a group called red dwarfs. A red dwarf is a star that is smaller and cooler than our Sun. L 98-59 has a surface temperature of 3,415 K (scientists use the Kelvin scale, where 0 K is the coldest anything can be — 3,415 K works out to roughly 3,140 degrees Celsius). Our own Sun’s surface sits closer to 5,778 K, so L 98-59 is noticeably cooler and redder.
Because red dwarfs put out less energy and light than our Sun, planets have to orbit much closer to them to receive any warmth at all. That is exactly what we see in this system. All five known planets crowd in tight around their star, completing their orbits in just a few Earth days each.
Red dwarfs are very common in our galaxy. Scientists think they make up the majority of all stars in the Milky Way. So studying a system like L 98-59 may teach us things that apply across a huge number of worlds.
How the Five Planets Were Found
The planets of L 98-59 were discovered using the transit method. A transit happens when a planet passes in front of its star, as seen from our direction. When that occurs, the star’s light dims slightly — just a tiny flicker. Sensitive telescopes can detect that flicker and use it to figure out that a planet is there, and even how big it is.
The first planets in this system were found in 2019. Astronomers — scientists who study space — spotted the dips in starlight and worked backward to understand what was causing them. Since then, further study has added more planets to the count, bringing the total to five as far as we know today.
The transit method is very good at measuring a planet’s size, because a bigger planet blocks more light. If scientists also have other data, such as tiny wobbles in the star caused by a planet’s gravity, they can sometimes figure out a planet’s mass too. Together, size and mass let researchers estimate what a planet might be made of.
Meet L 98-59 d
L 98-59 d is one of the best-studied members of this family. Its radius — the distance from its center to its surface — is 1.63 times Earth’s radius. Its mass is 1.64 times Earth’s mass. Those two numbers are very close to each other, which is an interesting clue. When a planet’s size and mass are roughly in the same proportion as Earth’s, scientists think it might have a rocky composition, though they are careful about drawing firm conclusions from that alone.
One orbit around L 98-59 takes just 7.45 Earth days for planet d. That means its year is less than two weeks long. It zips around its star at a pace that would feel dizzying to us, though of course no one is there to feel it.
You can explore this planet and others in the system explorer to see how d fits among its neighbors.
Temperature and What It Means for Planet d
Scientists estimate that L 98-59 d has a likely temperature of around 416 K, which is about 143 degrees Celsius. That is hotter than boiling water. At those temperatures, liquid water on the surface seems very unlikely, and the planet almost certainly does not sit in what scientists call the habitable zone — the range of distances from a star where liquid water could exist on a world’s surface.
It is important to say that this temperature estimate comes with uncertainty. The real surface temperature depends on things we do not know yet, like whether the planet has an atmosphere — a layer of gases — and what that atmosphere is made of. An atmosphere can trap heat or reflect it, pushing the actual temperature up or down. Scientists have not confirmed whether L 98-59 d has an atmosphere at all.
So while 416 K gives us a starting point, the true conditions on this world remain an open question. That is honest science: using the best estimate available while keeping the door open for new data.
The Other Four Worlds in the Family
L 98-59 d is not alone. Four other planets orbit L 98-59. Scientists have measured some of these worlds, but detailed data for all of them is not yet fully pinned down, so we will stay with what is well established.
What is clear is that the system holds a range of worlds. Some of the inner planets are quite small — scientists have described at least one as among the smallest exoplanets (planets outside our Solar System) that telescopes have been able to measure by mass. The outer planets are somewhat larger. Together, the five form a compact family, all tucked in close to their cool star.
The variety within this one system is part of what makes it interesting to researchers. Having multiple planets around the same star means scientists can compare them directly — same star, same starting materials, but possibly very different outcomes.
How This System Compares to Our Solar System
Our Solar System has eight planets spread across a vast range of distances. The zone where L 98-59’s five planets all orbit would fit comfortably inside Mercury’s orbit around our Sun. In other words, the whole L 98-59 system is squeezed into a space much smaller than the inner part of our own neighborhood.
Our planets also have a wide range of sizes, from small rocky worlds like Earth and Mars to gas giants like Jupiter and Saturn. The L 98-59 family, as far as we know, stays in a smaller size range — no giant planets have been confirmed there yet, though scientists continue to look.
These differences remind us that planetary systems come in many arrangements. Ours is not the template. The universe seems happy to build families of worlds in all kinds of ways.
What Scientists Hope to Learn Next
L 98-59 is close enough to Earth that modern telescopes can take a careful look. One of the biggest questions is whether any of these planets have atmospheres. Detecting an atmosphere around a small planet is very hard, but it is not impossible with the most powerful instruments available today.
If an atmosphere is found around one of the L 98-59 planets, scientists could begin to study what gases are in it. That would help them understand whether the planet formed rocky or icy, and how it has changed over time. It would also add to a growing picture of how common or rare certain kinds of worlds are across our galaxy.
For now, L 98-59 and its five planets stand as a good example of what careful, patient science can reveal — a whole family of worlds, 34.6 light-years away, slowly coming into focus.