HIP 9618 b
HIP 9618 b is a puffy low-density planet orbiting HIP 9618 in the constellation Aries. It lies about 220 light-years from Earth and was discovered in 2023 using the transit method.
How Big Is HIP 9618 b?
HIP 9618 b has a radius of 3.83 times that of Earth. Its mass is 8.3 times that of Earth, giving it a density of 0.81 g/cm³ — closer to gas planets like Jupiter (1.33 g/cm³).
Is HIP 9618 b in the Habitable Zone?
HIP 9618 b orbits inside the inner edge of the habitable zone of HIP 9618. So close to its star, surface conditions are far too hot for liquid water.
Habitable zone of HIP 9618: 0.696–1.647 AU (conservative: 0.882–1.561 AU), per Kopparapu et al. (2014). Earth orbits the Sun at 1 AU.
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Temperature on HIP 9618 b
The equilibrium temperature of HIP 9618 b is about 641 K (368 °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.
Orbit and Year Length
A year on HIP 9618 b — one full orbit around HIP 9618 — lasts 20.8 Earth days, shorter than Mercury's 88-day year. It orbits at an average distance of 0.145 AU — closer to its star than Mercury is to the Sun.
How Was HIP 9618 b Discovered?
HIP 9618 b was discovered in 2023 using the transit method, with observations from Transiting Exoplanet Survey Satellite (TESS).
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 HIP 9618 b?
HIP 9618 b is 220.3 light-years (67.5 parsecs) from Earth. Light arriving here tonight left the planet around the year 1806. A probe traveling at the speed of Voyager 1 — about 17 km/s, the fastest outbound spacecraft ever launched — would need roughly 3,877,280 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. HIP 9618 b scores 0.21, ranking #3,817 of 5,568 planets with a known ESI. For reference, Mars scores about 0.70.
The Host Star: HIP 9618
HIP 9618
- Surface temperature
- 5,649 K (Sun: 5,772 K)
- Mass
- 0.94 M☉
- Radius
- 0.96 R☉
- Luminosity
- 0.8480 L☉
- Age
- 5.6 billion years (Sun: 4.6)
The HIP 9618 Planetary System
HIP 9618 b is one of 2 known planets in the HIP 9618 system. Its siblings:
- HIP 9618 c (Puffy Planet)
HIP 9618 b — Complete Data
| Radius | 3.828 Earth radii (0.342 Jupiter radii) |
|---|---|
| Mass | 8.30 Earth masses (0.026 Jupiter masses) |
| Density | 0.81 g/cm³ (Earth: 5.51) |
| Orbital period | 20.77 days |
| Orbital distance | 0.145 AU |
| Equilibrium temperature | 641 K (368 °C) |
| Earth Similarity Index | 0.21 |
| Distance from Earth | 220.3 light-years (67.5 parsecs) |
| Constellation | Aries |
| Discovery method | Transit |
| Discovery facility | Transiting Exoplanet Survey Satellite (TESS) |
| Discovery year | 2023 |
Data: NASA Exoplanet Archive, last updated 2024-07-22. Earth Similarity Index: PHL @ UPR Arecibo.
Frequently Asked Questions About HIP 9618 b
Is HIP 9618 b habitable?
No — HIP 9618 b orbits too close to its star and is too hot for liquid water to exist on its surface.
How far away is HIP 9618 b?
HIP 9618 b is about 220 light-years from Earth in the constellation Aries. A spacecraft traveling as fast as Voyager 1 (about 17 km/s) would need roughly 3,877,280 years to get there.
How big is HIP 9618 b compared to Earth?
HIP 9618 b has 3.83 times the radius of Earth and about 8.3 times its mass.
How long is a year on HIP 9618 b?
One orbit around HIP 9618 takes 20.8 Earth days — short enough that 18 of its years would fit into one Earth year.
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