Kepler-1593 b is a world far beyond our solar system, sitting roughly 2,082 light-years away from Earth. Scientists spotted it in 2016, and it quickly caught attention for one simple reason: it sits in the region around its star where liquid water could exist. That does not mean it has water or life — but it does make it worth a closer look.
What We Know About Kepler-1593 b
Kepler-1593 b orbits a star called Kepler-1593. One full trip around that star takes 175 Earth days, which means its year is a little shorter than an Earth year. So far, it is the only planet scientists have found in this system.
The planet’s estimated temperature is about 260 K, which works out to roughly -13 degrees Celsius. That is colder than a freezing winter day, somewhere close to the kind of temperatures you might find near Earth’s polar regions. Scientists use the word “equilibrium temperature” — that is, the temperature a planet would be if it absorbed and released starlight perfectly evenly. The real surface temperature could be warmer or colder depending on whether the planet has an atmosphere (a layer of gas around it) and what that atmosphere is made of. Scientists haven’t measured those things for Kepler-1593 b yet.
As far as we know from the data collected so far, Kepler-1593 b is the only confirmed planet in its system. There could be others too small or too far away to have shown up in the observations.
A Star That Runs a Little Cooler
Every planet tells part of its story through its star. Kepler-1593 has a surface temperature of about 4,995 K. To give that some context, our own Sun runs at roughly 5,778 K. So Kepler-1593 is noticeably cooler than the Sun, though not by a huge amount.
Stars like this are sometimes called K-type stars — orange-yellow stars that are smaller and dimmer than our Sun but still fairly stable. They burn through their fuel more slowly than Sun-like stars, which means they tend to last a very long time. Some scientists think this kind of long-lived, steady star could actually be a good host for a planet that might one day support life, because it gives more time for interesting chemistry to develop. That said, this idea is still debated, and we should not jump to conclusions.
Because Kepler-1593 is cooler and puts out less energy than the Sun, its habitable zone — the band where water could be liquid — sits closer in than our Sun’s does. That is one reason Kepler-1593 b can orbit in just 175 days and still be in a promising position.
Inside the Habitable Zone
The habitable zone is the range of distances from a star where a rocky planet with the right atmosphere could, in theory, have liquid water on its surface. It is sometimes called the “Goldilocks zone” — not too hot, not too cold. Kepler-1593 b appears to sit inside this zone around its star, based on its orbit and the star’s energy output.
It helps to understand what the habitable zone is not. It is not a guarantee of life. It is not even a guarantee of water. It is simply the region where the conditions are not obviously ruled out. A planet too close to its star would boil away any oceans. A planet too far away would freeze everything solid. Being in the zone means a world avoids those two extremes — nothing more.
If you want to explore how the zone works for different types of stars, the habitable zone explorer on this site is a good place to start. You can also browse the most Earth-like worlds list to see how Kepler-1593 b compares with other candidates scientists are studying.
A Planet Much Bigger Than Earth
Kepler-1593 b is noticeably larger than our home planet. Its radius — that is, the distance from its center to its surface — is about 3.17 times Earth’s radius. Its mass is about 10.2 times Earth’s mass. Both of those numbers matter when scientists try to figure out what kind of world it is.
A planet with roughly these proportions often falls into a category scientists call a sub-Neptune or a super-Earth, depending on how you draw the lines. With a radius over three times Earth’s, many researchers would lean toward calling it a sub-Neptune. That word means a planet smaller than Neptune in our solar system but larger than Earth — a type of world we simply don’t have in our own neighborhood, which makes it harder to study.
Planets in this size range often have thick envelopes of gas or steam surrounding a rocky or icy core. If Kepler-1593 b does have a deep, dense atmosphere, that atmosphere could trap heat and raise the surface temperature well above the equilibrium estimate of -13°C. Or it might not have much of an atmosphere at all. Scientists haven’t been able to measure its atmosphere yet, so we genuinely don’t know.
What “Possible Water” Really Means
It is worth being honest about what science can and cannot say about Kepler-1593 b right now. The phrase “water might be possible” carries a lot of careful hedging. Here is what scientists actually know, and what they don’t.
- Known: The planet sits at a distance from its star where liquid water is not ruled out by temperature alone.
- Not yet known: Whether it has an atmosphere, and what that atmosphere contains.
- Not yet known: Whether its surface is rocky, icy, or covered in deep layers of gas.
- Not yet known: Whether any water exists there at all, in any form.
- Not known: Anything about signs of life.
Being in the habitable zone is a starting point, not a conclusion. It tells scientists that Kepler-1593 b is worth studying more closely. Future telescopes with the ability to analyze the chemistry of distant atmospheres might one day give us clearer answers.
How Scientists Found It
Kepler-1593 b was discovered in 2016 using the transit method. Here is how that works: when a planet passes in front of its star from our point of view, it blocks a tiny amount of the star’s light. Sensitive instruments can detect that small dip. By watching how often the dip repeats and how deep it is, scientists can work out how big the planet is and how long its orbit takes.
The transit method is very good at measuring a planet’s size. Mass is harder to pin down from transits alone, and requires additional techniques. The mass estimate of 10.2 times Earth’s comes with some uncertainty, as is normal for planets this far away.
At 2,082 light-years, Kepler-1593 b is far beyond anything humanity could ever visit with current technology. But distance does not stop science. Every careful measurement of a world like this one adds a small piece to a much larger picture — one that scientists are slowly building about what kinds of places, in all the universe, might one day turn out to be friendly to life.