Host star — Kepler-991
- Spectral type
- —
- Temperature
- 4,392 K
- Radius
- 0.61 R☉
- Mass
- 0.64 M☉
- Luminosity
- 0.148 L☉
- Distance
- 389.6 pc (1,271 ly)
Cooler than the Sun. Orange or red dwarf.
Kepler-991 b
Orbits Kepler-991 · 1,271 light-years from Earth
Neptune-likeTransit2016ESI 83 · Very Earth-like
Radius
2.54×
Earth
Mass
7.0×
Earth
Year
83d
Temp
260 K
-13°C
Gravity
1.1×
Earth
Distance
1,271
ly
What it would be like
Kepler-991 b is a Neptune-like world — probably wrapped in thick layers of hydrogen, helium, and ices. There may be no solid surface at all, just clouds all the way down.
Surface gravity is about 1.1g — noticeably heavier what you're used to on Earth.
With an equilibrium temperature around -13°C, this planet sits in the temperature range where liquid water could potentially exist on the surface — a key ingredient for life as we know it.
An orbital period of 83 days makes the year 4.4× shorter than Earth's. You'd celebrate your birthday more often here.
Earth comparison
Logarithmic bars so Jupiter-class planets fit the same scale as Earth-size worlds.
Radius2.54R⊕
1/25×Earth = 125×
Mass6.99M⊕
1/10000×Earth = 110000×
Surface gravity1.08g
1/100×Earth = 1100×
Equilibrium temp260 K(-13°C)
0 KEarth 255 K2500 K
Side-by-side with Earth
Temperature in context
Liquid N₂Mars avgEarth eq.Earth sfc.Boiling H₂OVenus
Discovery & orbit
- Method
- Transit
- Year
- 2016
- Facility
- Kepler
- Semi-major axis
- 0.3104 AU
- Period
- 82.53 days
- Eccentricity
- 0.0000
- Density
- 2.34 g/cm³
Detected by measuring the tiny dip in starlight as the planet crosses in front of its star.
Nearly circular orbit.
Low density — probably icy or gas-rich.
Discovered via · Transit
Tiny dip in starlight as the planet crosses in front of its star
A transit photometer watches a star nonstop and measures its brightness to ~0.01%. When a planet passes between us and the star, the star dims briefly — the deeper the dip, the bigger the planet. This is how Kepler and TESS found most known exoplanets.
- Overall share
- ~75% of all confirmed worlds
- Best for
- Earth-to-Neptune-sized planets on short orbits
Orbital Animation
Kepler-991Kepler-991 bOrbitEarth orbitHabitable zone
Drag to rotate · scroll to zoomSemi-major axis: 0.310 AUEccentricity: 0.0000Period: 82.5 days
Hertzsprung–Russell Diagram
Where this host star sits among … exoplanet host stars. The main sequence band runs diagonally — giants and supergiants sit above, white dwarfs below.
OBAFGKMCurrent star
How far is 1,271 light-years?
- A light beam leaving Earth right now would arrive in 1,271 years.
- At Voyager 1's speed (17 km/s), the trip would take approximately 22.4 million years.
- A radio signal sent today would arrive in 1270.6 years — and the reply wouldn't come back for twice that.
Earth Similarity Index
83/1000 — Nothing like Earth100 — Identical to Earth
ESI combines radius similarity and equilibrium temperature similarity. Earth = 100. Mars ≈ 73. Venus ≈ 44. This score reflects two physical parameters only — not atmosphere, water, or magnetic field.