eps Ind A b is one of the closest known exoplanets — worlds that orbit stars other than our Sun — to Earth. It sits just 11.9 light-years away, which sounds small on a cosmic scale, yet is still an almost unimaginable distance by any human measure. Getting to know this world means thinking carefully about what that distance actually feels like.
Meet the Star: eps Ind A
Every planet needs a star, and eps Ind A b orbits a star called eps Ind A. This star sits in the southern constellation Indus, and it is one of our closer stellar neighbors. Stars are sorted by their surface temperature, and eps Ind A has a surface temperature of 4,760 K — that stands for Kelvin, which is a temperature scale scientists use. For comparison, our Sun’s surface is about 5,778 K, so eps Ind A runs a little cooler and glows with a slightly more orange tint than our yellow-white Sun. Cooler stars like this are called K-type stars, and they are quite common in our galaxy.
As far as scientists know, eps Ind A b is the only planet found in this system so far. That doesn’t mean the system is empty — it just means no other planets have been detected yet.
How Far Is 11.9 Light-Years, Really?
A light-year is the distance light travels in one full year. Light moves at about 300,000 kilometers every single second, so in a year it covers roughly 9.5 trillion kilometers. Multiply that by 11.9 and you get a number so large it is hard to picture.
Here are a few comparisons that might help:
- The Moon is about 1.3 light-seconds away. A radio signal from Earth reaches it in just over a second.
- The Sun is about 8 light-minutes away. Sunlight takes around 8 minutes to reach us.
- The nearest star to our Sun, Proxima Centauri, is about 4.2 light-years away.
- eps Ind A b is nearly three times farther than Proxima Centauri.
Still, 11.9 light-years places eps Ind A b firmly in our cosmic backyard. Our galaxy, the Milky Way, is about 100,000 light-years across. On that scale, this planet is practically next door. You can explore how our nearest neighbors are arranged by visiting the Cosmic Map, which puts distances like this into a wider picture.
Traveling There — How Long Would It Take?
Knowing the distance in light-years is one thing. Imagining a real journey there is something else entirely.
The fastest spacecraft humans have ever launched is the Voyager 1 probe. It travels at roughly 17 kilometers per second. That sounds quick, but at that speed, reaching eps Ind A b would take well over 200,000 years. No one alive today — or anyone in recorded history — would come close to finishing that trip.
What if we could travel much faster? Even at one percent of the speed of light — far beyond anything we can build today — the journey would still take about 1,190 years. At ten percent of the speed of light, a speed that remains purely theoretical for a crewed ship, it would take roughly 119 years. These numbers show why reaching even our nearest stellar neighbors is one of the greatest unsolved challenges in science and engineering. If you want to play with these numbers yourself, the distance and travel time tool lets you try different speeds and see how long the trip would take.
Light itself, the fastest thing in the universe as far as we know, takes 11.9 years to make the crossing. Any radio message we sent today would arrive there in 11.9 years — and a reply would take another 11.9 years to return. That one-way delay makes even a simple conversation across this distance a multigenerational exercise in patience.
What We Know About eps Ind A b
eps Ind A b is a large world. Its radius — the distance from the center of the planet to its surface — is about 12.6 times Earth’s radius. Its mass is around 2,425 times the mass of Earth. Those numbers put it in a category far above our own planet and well beyond even the giant planets in our solar system like Jupiter and Saturn. Scientists think it may be more similar in nature to those gas giants than to a rocky world like Earth, though exactly what lies beneath its outer layers is not yet well understood.
Scientists have estimated a likely temperature of around 275 K, which works out to about 2 degrees Celsius — just above the freezing point of water. That temperature refers to the planet’s outer atmosphere as scientists understand it so far, not necessarily a surface you could stand on. Whether that figure tells us anything about conditions deeper inside the planet, scientists haven’t yet determined.
One orbit around eps Ind A takes approximately 39,400 Earth days. To put that in perspective, one orbit is roughly 108 Earth years. A year on eps Ind A b lasts longer than a full human lifetime. This very long orbital period means the planet sits far from its star, in a wide, slow path through space.
How Scientists Found It
eps Ind A b was discovered in 2019 using a method called Radial Velocity. This technique works by watching for tiny wobbles in a star’s light. When a planet orbits a star, its gravity gives the star a slight tug. That tug causes the star to rock back and forth just a little. As the star moves toward Earth, its light waves get slightly compressed. As it moves away, they stretch out. Scientists can measure these tiny shifts in the light very carefully, and from those shifts they can work out that a planet must be there — and get a rough sense of its mass.
The Radial Velocity method doesn’t let scientists see the planet directly. It’s more like noticing that a ball is rolling inside a bag by watching the bag move. That’s part of why some details about eps Ind A b — like its exact composition or what its atmosphere might contain — are still unknown. The measurements that have been made, though, are enough to confirm that something large is really there.
A Giant World in a Giant Orbit
eps Ind A b sits in a remarkable position in our sky. It is close enough to study in more detail as telescope technology improves, yet distant enough to remind us how much we still don’t know about the worlds nearest to us. With a year lasting over a century and a size that dwarfs anything in our solar system, it shows that planets come in ranges we are still learning to fully understand. At 11.9 light-years, it is a near neighbor in space terms — and yet, by any human scale, it remains beautifully, wonderfully far away.