HD 42618 b
HD 42618 b is a Neptune-like planet orbiting the G4 V star HD 42618 in the constellation Orion. It lies about 79 light-years from Earth and was discovered in 2016 using the radial velocity method.
Is HD 42618 b in the Habitable Zone?
HD 42618 b orbits inside the inner edge of the habitable zone of HD 42618. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of HD 42618: 0.745–1.758 AU (conservative: 0.944–1.667 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on HD 42618 b
The equilibrium temperature of HD 42618 b is about 337 K (64 °C) — hotter than anywhere on Earth. This estimate ignores any atmosphere, which could change surface temperatures dramatically — Earth's greenhouse effect adds about 33 °C. It receives 3.16 times the stellar energy that Earth gets from the Sun.
Orbit and Year Length
A year on HD 42618 b — one full orbit around HD 42618 — lasts 149.6 Earth days, between the years of Mercury (88 days) and Earth (365 days). It orbits at an average distance of 0.554 AU — comparable to the inner Solar System. Its orbit is mildly elliptical (eccentricity 0.19).
How Was HD 42618 b Discovered?
HD 42618 b was discovered in 2016 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 42618 b?
HD 42618 b is 79.4 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 1,397,440 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 42618 b scores 0.44, ranking #362 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HD 42618
HD 42618
- Spectral type
- G4 V
- Surface temperature
- 5,727 K (Sun: 5,772 K)
- Mass
- 1.01 M☉
- Radius
- 1.00 R☉
- Luminosity
- 0.9800 L☉
Planetary System
HD 42618 b is the only planet known to orbit HD 42618 so far.
HD 42618 b — Complete Data
| Mass (best estimate) | 14.40 Earth masses |
|---|---|
| Orbital period | 149.61 days |
| Orbital distance | 0.554 AU |
| Eccentricity | 0.190 |
| Equilibrium temperature | 337 K (64 °C) |
| Stellar irradiation | 3.16× Earth |
| Earth Similarity Index | 0.44 |
| Distance from Earth | 79.4 light-years (24.3 parsecs) |
| Constellation | Orion |
| Discovery method | Radial Velocity |
| Discovery facility | Multiple Observatories |
| Discovery year | 2016 |
Data: NASA Exoplanet Archive, last updated 2016-10-26. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HD 42618 b
Is HD 42618 b habitable?
No — HD 42618 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is HD 42618 b?
HD 42618 b is about 79 light-years from Earth in the constellation Orion. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 1,397,440 years to get there.
How long is a year on HD 42618 b?
One orbit around HD 42618 takes 149.6 Earth days.
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