HD 199509 b
HD 199509 b is a Neptune-like planet orbiting HD 199509 in the constellation Octans. It lies about 79 light-years from Earth and was discovered in 2022 using the radial velocity method.
Is HD 199509 b in the Habitable Zone?
The position of HD 199509 b relative to the habitable zone of HD 199509 cannot be precisely determined from the available orbital data.
Orbit and Year Length
A year on HD 199509 b — one full orbit around HD 199509 — lasts 99.6 Earth days, between the years of Mercury (88 days) and Earth (365 days). It orbits at an average distance of 0.426 AU — comparable to the inner Solar System. Its orbit is highly elliptical (eccentricity 0.37), swinging dramatically closer to and farther from its star.
How Was HD 199509 b Discovered?
HD 199509 b was discovered in 2022 using the radial velocity method, with observations from Multiple Observatories.
The radial velocity method measures the subtle wobble of a star caused by the gravitational pull of an orbiting planet, visible as periodic shifts in the star's light spectrum. The size of the wobble reveals the planet's minimum mass.
How Far Away Is HD 199509 b?
HD 199509 b is 79.3 light-years (24.3 parsecs) from Earth. Light arriving here tonight left the planet around the year 1947. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 1,395,680 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. HD 199509 b scores 0.29, ranking #2,015 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HD 199509
HD 199509
- Mass
- 1.04 M☉
Planetary System
HD 199509 b is the only planet known to orbit HD 199509 so far.
HD 199509 b — Complete Data
| Mass (best estimate) | 43.22 Earth masses |
|---|---|
| Orbital period | 99.62 days |
| Orbital distance | 0.426 AU |
| Eccentricity | 0.373 |
| Earth Similarity Index | 0.29 |
| Distance from Earth | 79.3 light-years (24.3 parsecs) |
| Constellation | Octans |
| Discovery method | Radial Velocity |
| Discovery facility | Multiple Observatories |
| Discovery year | 2022 |
Data: NASA Exoplanet Archive, last updated 2023-06-14. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HD 199509 b
Is HD 199509 b habitable?
HD 199509 b is not known to orbit within the habitable zone of HD 199509, and as a Neptune-like planet it is an unlikely candidate for life as we know it.
How far away is HD 199509 b?
HD 199509 b is about 79 light-years from Earth in the constellation Octans. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 1,395,680 years to get there.
How long is a year on HD 199509 b?
One orbit around HD 199509 takes 99.6 Earth days.
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