NGTS-8 b
NGTS-8 b is a hot Jupiter orbiting the K0 V star NGTS-8 in the constellation Capricornus. It lies about 1,399 light-years from Earth and was discovered in 2019 using the transit method.
How Big Is NGTS-8 b?
NGTS-8 b has a radius of 12.22 times that of Earth, or 1.09 times the radius of Jupiter. Its mass is 296 times that of Earth, giving it a density of 0.89 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is NGTS-8 b in the Habitable Zone?
NGTS-8 b orbits inside the inner edge of the habitable zone of NGTS-8. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of NGTS-8: 0.624–1.495 AU (conservative: 0.790–1.417 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on NGTS-8 b
The equilibrium temperature of NGTS-8 b is about 1,345 K (1,072 °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 503 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on NGTS-8 b — one full orbit around NGTS-8 — lasts 2.50 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.035 AU — closer to its star than Mercury is to the Sun. Its orbit is nearly circular (eccentricity 0.010).
How Was NGTS-8 b Discovered?
NGTS-8 b was discovered in 2019 using the transit method, with observations from Next-Generation Transit Survey (NGTS).
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 NGTS-8 b?
NGTS-8 b is 1,399.1 light-years (429.0 parsecs) from Earth. Light arriving here tonight left the planet about 1,399 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 24,624,160 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. NGTS-8 b scores 0.07, ranking #4,801 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: NGTS-8
NGTS-8
- Spectral type
- K0 V
- Surface temperature
- 5,241 K (Sun: 5,772 K)
- Mass
- 0.89 M☉
- Radius
- 0.98 R☉
- Age
- 12.5 billion years (Sun: 4.6)
Planetary System
NGTS-8 b is the only planet known to orbit NGTS-8 so far.
NGTS-8 b — Complete Data
| Radius | 12.218 Earth radii (1.090 Jupiter radii) |
|---|---|
| Mass | 295.58 Earth masses (0.930 Jupiter masses) |
| Density | 0.89 g/cm³ (Earth: 5.51) |
| Orbital period | 2.50 days |
| Orbital distance | 0.035 AU |
| Eccentricity | 0.010 |
| Equilibrium temperature | 1,345 K (1,072 °C) |
| Stellar irradiation | 503.00× Earth |
| Earth Similarity Index | 0.07 |
| Distance from Earth | 1,399.1 light-years (429.0 parsecs) |
| Constellation | Capricornus |
| Discovery method | Transit |
| Discovery facility | Next-Generation Transit Survey (NGTS) |
| Discovery year | 2019 |
Data: NASA Exoplanet Archive, last updated 2019-11-18. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About NGTS-8 b
Is NGTS-8 b habitable?
No — NGTS-8 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is NGTS-8 b?
NGTS-8 b is about 1,399 light-years from Earth in the constellation Capricornus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 24,624,160 years to get there.
How big is NGTS-8 b compared to Earth?
NGTS-8 b has 12.22 times the radius of Earth and about 296 times its mass.
How long is a year on NGTS-8 b?
One orbit around NGTS-8 takes 2.5 Earth days — short enough that 146 of its years would fit into one Earth year.
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