KELT-20 b
KELT-20 b is a hot Jupiter orbiting the A2 V star KELT-20 in the constellation Cygnus. It lies about 445 light-years from Earth and was discovered in 2017 using the transit method.
How Big Is KELT-20 b?
KELT-20 b has a radius of 19.51 times that of Earth, or 1.74 times the radius of Jupiter. Its mass is 1,075 times that of Earth, giving it a density of 0.81 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is KELT-20 b in the Habitable Zone?
The position of KELT-20 b relative to the habitable zone of KELT-20 cannot be precisely determined from the available orbital data.
Temperature on KELT-20 b
The equilibrium temperature of KELT-20 b is about 2,262 K (1,989 °C) — hot enough to melt many metals. This estimate ignores any atmosphere, which could change surface temperatures dramatically — Earth's greenhouse effect adds about 33 °C. It receives 4,363 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on KELT-20 b — one full orbit around KELT-20 — lasts 3.47 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.054 AU — closer to its star than Mercury is to the Sun.
How Was KELT-20 b Discovered?
KELT-20 b was discovered in 2017 using the transit method, with observations from KELT-North.
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 KELT-20 b?
KELT-20 b is 445.0 light-years (136.4 parsecs) from Earth. Light arriving here tonight left the planet around the year 1581. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 7,832,000 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. KELT-20 b scores 0.05, ranking #5,296 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: KELT-20
KELT-20
- Spectral type
- A2 V
- Surface temperature
- 8,720 K (Sun: 5,772 K)
- Mass
- 1.76 M☉
- Radius
- 1.57 R☉
- Luminosity
- 12.6999 L☉
- Age
- 0.6 billion years (Sun: 4.6)
Planetary System
KELT-20 b is the only planet known to orbit KELT-20 so far.
KELT-20 b — Complete Data
| Radius | 19.515 Earth radii (1.741 Jupiter radii) |
|---|---|
| Mass | 1,074.90 Earth masses (3.382 Jupiter masses) |
| Density | 0.81 g/cm³ (Earth: 5.51) |
| Orbital period | 3.47 days |
| Orbital distance | 0.054 AU |
| Equilibrium temperature | 2,262 K (1,989 °C) |
| Stellar irradiation | 4,362.50× Earth |
| Earth Similarity Index | 0.05 |
| Distance from Earth | 445.0 light-years (136.4 parsecs) |
| Constellation | Cygnus |
| Discovery method | Transit |
| Discovery facility | KELT-North |
| Discovery year | 2017 |
Data: NASA Exoplanet Archive, last updated 2019-12-02. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About KELT-20 b
Is KELT-20 b habitable?
KELT-20 b is not known to orbit within the habitable zone of KELT-20, and as a hot Jupiter it is an unlikely candidate for life as we know it.
How far away is KELT-20 b?
KELT-20 b is about 445 light-years from Earth in the constellation Cygnus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 7,832,000 years to get there.
How big is KELT-20 b compared to Earth?
KELT-20 b has 19.51 times the radius of Earth and about 1,075 times its mass.
How long is a year on KELT-20 b?
One orbit around KELT-20 takes 3.5 Earth days — short enough that 105 of its years would fit into one Earth year.
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