HD 117618 b
HD 117618 b is a cold gas giant orbiting HD 117618 in the constellation Centaurus. It lies about 123 light-years from Earth and was discovered in 2004 using the radial velocity method.
Is HD 117618 b in the Habitable Zone?
The position of HD 117618 b relative to the habitable zone of HD 117618 cannot be precisely determined from the available orbital data.
Orbit and Year Length
A year on HD 117618 b — one full orbit around HD 117618 — lasts 25.8 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.180 AU — closer to its star than Mercury is to the Sun. Its orbit is mildly elliptical (eccentricity 0.15).
How Was HD 117618 b Discovered?
HD 117618 b was discovered in 2004 using the radial velocity method, with observations from Anglo-Australian Telescope.
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 117618 b?
HD 117618 b is 123.2 light-years (37.8 parsecs) from Earth. Light arriving here tonight left the planet around the year 1903. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 2,168,320 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 117618 b scores 0.12, ranking #4,335 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HD 117618
HD 117618
- Surface temperature
- 5,990 K (Sun: 5,772 K)
- Mass
- 1.08 M☉
Planetary System
HD 117618 b is the only planet known to orbit HD 117618 so far.
HD 117618 b — Complete Data
| Mass (best estimate) | 55.30 Earth masses |
|---|---|
| Orbital period | 25.80 days |
| Orbital distance | 0.180 AU |
| Eccentricity | 0.150 |
| Earth Similarity Index | 0.12 |
| Distance from Earth | 123.2 light-years (37.8 parsecs) |
| Constellation | Centaurus |
| Discovery method | Radial Velocity |
| Discovery facility | Anglo-Australian Telescope |
| Discovery year | 2004 |
Data: NASA Exoplanet Archive, last updated 2019-03-11. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HD 117618 b
Is HD 117618 b habitable?
HD 117618 b is not known to orbit within the habitable zone of HD 117618, and as a cold gas giant it is an unlikely candidate for life as we know it.
How far away is HD 117618 b?
HD 117618 b is about 123 light-years from Earth in the constellation Centaurus. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 2,168,320 years to get there.
How long is a year on HD 117618 b?
One orbit around HD 117618 takes 25.8 Earth days — short enough that 14 of its years would fit into one Earth year.
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