About the image. Drawn as an icy planet with one open ocean facing its star, the 'eyeball' scenario researchers have proposed. The planet could also be a frozen snowball or a small gas-rich mini-Neptune.
2.3×as wide as our Sun looks from Earth
43%of the light Earth gets
The sky from LHS 1140 b
LHS 1140 would look 2.3× as wide as the Sun does from Earth, and the planet gets 43% of the light Earth gets from the Sun.
Its colour comes from its surface temperature of 3 096 K (2 820 °C); the Sun's is about 5 772 K (5 500 °C).
How fast LHS 1140 b spins is unknown, so the length of its day is too.
Apparent size = star radius ÷ orbit; light = size² × (temperature ÷ 5 772 K)⁴. Both from the values on this page. The landscape is imagined.
LHS 1140 b was announced in April 2017 by Jason Dittmann and the MEarth team: a super-Earth crossing a small red dwarf 49 light-years away, in its habitable zone. The first measurements made it extraordinarily dense, about 12.5 grams per cubic centimetre, one of the densest rocky planets known, perhaps with an iron core three-quarters of its mass.
Too light to be rock
Better data told a different story. In 2024 Charles Cadieux and colleagues measured it at 1.73 times Earth’s width and 5.6 times its mass. That is too light for solid rock. Either it is a water world, with water making up somewhere between 9 and 19 percent of its mass, or it is a small mini-Neptune with a thick gas envelope. LHS 1140 b is one of very few potentially habitable planets whose mass and radius have both been measured, so these numbers matter.
What JWST saw
Also in 2024, a study titled “LHS 1140 b is a Potentially Habitable Water World” used the James Webb Space Telescope to rule out a thick hydrogen-rich atmosphere. That weakens the mini-Neptune idea. Hints of nitrogen were reported but need confirming.
The planet gets about 43 percent of the light Earth receives. Without an atmosphere it would be a snowball, covered in ice. With a greenhouse effect twice as strong as Earth’s, models put the surface near room temperature, about 23 °C. One proposed picture is an “eyeball” world: ice everywhere except a round open ocean on the side facing the star.
The star helps. LHS 1140 is a very quiet red dwarf that has not been seen to flare violently, unlike many of its kind. In 2026 a team reported helium escaping from the planet, which would mean it still holds an atmosphere, but other observations found no helium. The question is open.
Its orbit, to scale
LHS 1140 b goes around once every 25 days, at 0.0946 AU from its star. The whole view is tiny on Solar System scale: Mercury orbits the Sun about 4 times farther out than the outermost orbit shown here.
LHS 1140 b: equilibrium temperature. Logarithmic scale from 100 K to 10 000 K. Reference values: NASA, IAU.
How long to get there?
LHS 1140 b is about 49 light-years away.
Light299 792 km/s49 years
Breakthrough Starshotplanned light sail, 20% of light speed245 years
Parker Solar Probefastest spacecraft so far, 192 km/s76 509 years
Voyager 1leaving the Solar System, 17 km/s864 106 years
At Voyager 1's speed the trip would take about 10 801 human lifetimes of 80 years. Bars are on a logarithmic scale. Speeds: NASA, Breakthrough Initiatives.
Your weight on LHS 1140 b
On LHS 1140 b
Gravity there is about 1.87× Earth's. Calculated from the measured mass and radius.
Gallery
A white, icy planet with one large dark blue patch on its face, lit by a small red star on the left, an impression of LHS 1140 b. AI-generated painting.The edge of a white ice sheet meeting dark open water, with a faint red star on the horizon, an impression of the surface of LHS 1140 b. AI-generated painting.LHS 1140 b, 3D artist's impression, rendered from the interactive model.LHS 1140 b, 3D artist's impression, from another angle, rendered from the interactive model.LHS 1140 b, 3D artist's impression, close-up, rendered from the interactive model.
Timeline
2017Announced as a dense rocky super-Earth in its star's habitable zone.
2020Possible water vapour reported from Hubble data, at low confidence.
2024New mass and radius make it too light for rock: a water world or a mini-Neptune.
2024JWST rules out a thick hydrogen-rich atmosphere.
2026Escaping helium is reported, and disputed by other observations.
Questions people ask
Is LHS 1140 b a water world?
Possibly. Its density fits a planet with 9 to 19% water by mass, but a small gas-rich mini-Neptune is not ruled out.
What is an eyeball planet?
A frozen world with one round area of open ocean on the side that always faces its star, like the iris of an eye.