NGTS-9 b
NGTS-9 b is a hot Jupiter orbiting the F8 V star NGTS-9 in the constellation Hydra. It lies about 1,987 light-years from Earth and was discovered in 2019 using the transit method.
How Big Is NGTS-9 b?
NGTS-9 b has a radius of 11.99 times that of Earth, or 1.07 times the radius of Jupiter. Its mass is 922 times that of Earth, giving it a density of 2.93 g/cm³ — between that of rocky and gaseous planets.
Is NGTS-9 b in the Habitable Zone?
NGTS-9 b orbits inside the inner edge of the habitable zone of NGTS-9. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of NGTS-9: 1.202–2.798 AU (conservative: 1.522–2.653 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on NGTS-9 b
The equilibrium temperature of NGTS-9 b is about 1,448 K (1,175 °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 729 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on NGTS-9 b — one full orbit around NGTS-9 — lasts 4.44 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.058 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.06).
How Was NGTS-9 b Discovered?
NGTS-9 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-9 b?
NGTS-9 b is 1,986.7 light-years (609.1 parsecs) from Earth. Light arriving here tonight left the planet about 1,987 years ago. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 34,965,920 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-9 b scores 0.08, ranking #4,780 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: NGTS-9
NGTS-9
- Spectral type
- F8 V
- Surface temperature
- 6,330 K (Sun: 5,772 K)
- Mass
- 1.34 M☉
- Radius
- 1.38 R☉
- Age
- 1.0 billion years (Sun: 4.6)
Planetary System
NGTS-9 b is the only planet known to orbit NGTS-9 so far.
NGTS-9 b — Complete Data
| Radius | 11.994 Earth radii (1.070 Jupiter radii) |
|---|---|
| Mass | 921.71 Earth masses (2.900 Jupiter masses) |
| Density | 2.93 g/cm³ (Earth: 5.51) |
| Orbital period | 4.44 days |
| Orbital distance | 0.058 AU |
| Eccentricity | 0.060 |
| Equilibrium temperature | 1,448 K (1,175 °C) |
| Stellar irradiation | 729.00× Earth |
| Earth Similarity Index | 0.08 |
| Distance from Earth | 1,986.7 light-years (609.1 parsecs) |
| Constellation | Hydra |
| 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-9 b
Is NGTS-9 b habitable?
No — NGTS-9 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is NGTS-9 b?
NGTS-9 b is about 1,987 light-years from Earth in the constellation Hydra. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 34,965,920 years to get there.
How big is NGTS-9 b compared to Earth?
NGTS-9 b has 11.99 times the radius of Earth and about 922 times its mass.
How long is a year on NGTS-9 b?
One orbit around NGTS-9 takes 4.4 Earth days — short enough that 82 of its years would fit into one Earth year.
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