KELT-4 A b
KELT-4 A b is a hot Jupiter orbiting the F star KELT-4 A in the constellation Leo. It lies about 711 light-years from Earth and was discovered in 2016 using the transit method.
How Big Is KELT-4 A b?
KELT-4 A b has a radius of 19.04 times that of Earth, or 1.70 times the radius of Jupiter. Its mass is 287 times that of Earth, giving it a density of 0.23 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is KELT-4 A b in the Habitable Zone?
KELT-4 A b orbits inside the inner edge of the habitable zone of KELT-4 A. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of KELT-4 A: 1.354–3.159 AU (conservative: 1.715–2.995 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
See the full interactive habitable-zone view in the Exoplanet Explorer app ›
Temperature on KELT-4 A b
The equilibrium temperature of KELT-4 A b is about 1,823 K (1,550 °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 1,840 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on KELT-4 A b — one full orbit around KELT-4 A — lasts 2.99 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.043 AU — closer to its star than Mercury is to the Sun.
How Was KELT-4 A b Discovered?
KELT-4 A b was discovered in 2016 using the transit method, with observations from KELT.
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-4 A b?
KELT-4 A b is 711.2 light-years (218.1 parsecs) from Earth. Light arriving here tonight left the planet around the year 1315. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 12,517,120 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-4 A b scores 0.05, ranking #5,289 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: KELT-4 A
KELT-4 A b belongs to a system of 3 stars; it orbits KELT-4 A.
KELT-4 A
- Spectral type
- F
- Surface temperature
- 6,206 K (Sun: 5,772 K)
- Mass
- 1.20 M☉
- Radius
- 1.60 R☉
- Luminosity
- 3.4300 L☉
- Age
- 4.4 billion years (Sun: 4.6)
Planetary System
KELT-4 A b is the only planet known to orbit KELT-4 A so far.
KELT-4 A b — Complete Data
| Radius | 19.044 Earth radii (1.699 Jupiter radii) |
|---|---|
| Mass | 286.68 Earth masses (0.902 Jupiter masses) |
| Density | 0.23 g/cm³ (Earth: 5.51) |
| Orbital period | 2.99 days |
| Orbital distance | 0.043 AU |
| Equilibrium temperature | 1,823 K (1,550 °C) |
| Stellar irradiation | 1,840.00× Earth |
| Earth Similarity Index | 0.05 |
| Distance from Earth | 711.2 light-years (218.1 parsecs) |
| Constellation | Leo |
| Discovery method | Transit |
| Discovery facility | KELT |
| Discovery year | 2016 |
Data: NASA Exoplanet Archive, last updated 2021-05-17. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About KELT-4 A b
Is KELT-4 A b habitable?
No — KELT-4 A b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is KELT-4 A b?
KELT-4 A b is about 711 light-years from Earth in the constellation Leo. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 12,517,120 years to get there.
How big is KELT-4 A b compared to Earth?
KELT-4 A b has 19.04 times the radius of Earth and about 287 times its mass.
How long is a year on KELT-4 A b?
One orbit around KELT-4 A takes 3.0 Earth days — short enough that 122 of its years would fit into one Earth year.
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