HD 153557 c
HD 153557 c is a Neptune-like planet orbiting HD 153557 in the constellation Hercules. It lies about 59 light-years from Earth and was discovered in 2022 using the radial velocity method.
Is HD 153557 c in the Habitable Zone?
The position of HD 153557 c relative to the habitable zone of HD 153557 cannot be precisely determined from the available orbital data.
Orbit and Year Length
A year on HD 153557 c — one full orbit around HD 153557 — lasts 15.3 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.111 AU — closer to its star than Mercury is to the Sun. Its orbit is highly elliptical (eccentricity 0.51), swinging dramatically closer to and farther from its star.
How Was HD 153557 c Discovered?
HD 153557 c 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 153557 c?
HD 153557 c is 58.5 light-years (17.9 parsecs) from Earth. Light arriving here tonight left the planet around the year 1968. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 1,029,600 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 153557 c scores 0.21, ranking #3,782 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HD 153557
HD 153557
- Mass
- 0.79 M☉
The HD 153557 Planetary System
HD 153557 c is one of 3 known planets in the HD 153557 system. Its siblings:
- HD 153557 b (Neptune-like)
- HD 153557 d
HD 153557 c — Complete Data
| Mass (best estimate) | 17.48 Earth masses |
|---|---|
| Orbital period | 15.27 days |
| Orbital distance | 0.111 AU |
| Eccentricity | 0.511 |
| Earth Similarity Index | 0.21 |
| Distance from Earth | 58.5 light-years (17.9 parsecs) |
| Constellation | Hercules |
| 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 153557 c
Is HD 153557 c habitable?
HD 153557 c is not known to orbit within the habitable zone of HD 153557, and as a Neptune-like planet it is an unlikely candidate for life as we know it.
How far away is HD 153557 c?
HD 153557 c is about 59 light-years from Earth in the constellation Hercules. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 1,029,600 years to get there.
How long is a year on HD 153557 c?
One orbit around HD 153557 takes 15.3 Earth days — short enough that 24 of its years would fit into one Earth year.
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