Kepler-1999 b
Kepler-1999 b is a sub-Neptune orbiting Kepler-1999 in the constellation Draco. It lies about 2,287 light-years from Earth and was discovered in 2023 using the transit method.
How Big Is Kepler-1999 b?
Kepler-1999 b has a radius of 3.29 times that of Earth.
Is Kepler-1999 b in the Habitable Zone?
Kepler-1999 b orbits inside the inner edge of the habitable zone of Kepler-1999. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of Kepler-1999: 0.293–0.727 AU (conservative: 0.371–0.689 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on Kepler-1999 b
The equilibrium temperature of Kepler-1999 b is about 577 K (304 °C) — hotter than anywhere on Earth. This estimate ignores any atmosphere, which could change surface temperatures dramatically — Earth's greenhouse effect adds about 33 °C. It receives 26.17 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on Kepler-1999 b — one full orbit around Kepler-1999 — lasts 8.74 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.071 AU — closer to its star than Mercury is to the Sun.
How Was Kepler-1999 b Discovered?
Kepler-1999 b was discovered in 2023 using the transit method, with observations from Kepler.
The transit method watches a star for the tiny, regular dip in brightness that occurs when a planet crosses in front of it. The depth and timing of these dips reveal the planet's size and orbital period.
How Far Away Is Kepler-1999 b?
Kepler-1999 b is 2,287.2 light-years (701.3 parsecs) from Earth. Light arriving here tonight left the planet about 2,287 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 40,254,720 years to make the journey.
Earth Similarity Index
The Earth Similarity Index (ESI) scores how physically similar a planet is to Earth, from 0 to 1, based on radius, density, escape velocity and surface temperature. Kepler-1999 b scores 0.23, ranking #3,427 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: Kepler-1999
Kepler-1999
- Surface temperature
- 4,406 K (Sun: 5,772 K)
- Mass
- 0.63 M☉
- Radius
- 0.63 R☉
Planetary System
Kepler-1999 b is the only planet known to orbit Kepler-1999 so far.
Kepler-1999 b — Complete Data
| Radius | 3.290 Earth radii (0.294 Jupiter radii) |
|---|---|
| Orbital period | 8.74 days |
| Orbital distance | 0.071 AU |
| Equilibrium temperature | 577 K (304 °C) |
| Stellar irradiation | 26.17× Earth |
| Earth Similarity Index | 0.23 |
| Distance from Earth | 2,287.2 light-years (701.3 parsecs) |
| Constellation | Draco |
| Discovery method | Transit |
| Discovery facility | Kepler |
| Discovery year | 2023 |
Data: NASA Exoplanet Archive, last updated 2017-05-08. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About Kepler-1999 b
Is Kepler-1999 b habitable?
No — Kepler-1999 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is Kepler-1999 b?
Kepler-1999 b is about 2,287 light-years from Earth in the constellation Draco. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 40,254,720 years to get there.
How big is Kepler-1999 b compared to Earth?
Kepler-1999 b has 3.29 times the radius of Earth.
How long is a year on Kepler-1999 b?
One orbit around Kepler-1999 takes 8.7 Earth days — short enough that 42 of its years would fit into one Earth year.
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