HD 153557 d
Astrophysical Synthesis & Habitability Characterization
HD 153557 d is a confirmed gas giant exoplanet orbiting the star HD 153557, located approximately 58.5 light-years (17.94 parsecs) from the Solar System. First announced in 2022 by Multiple Observatories using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 11.9 Earth radii (1.06 Jupiter radii) and has a measured mass of 8725.661 Earth masses (27.45 Jupiter masses). Combining its mass and radius yields a mean bulk density of 28.55 g/cm³ (an iron-enriched, high-compression rocky core), a surface gravity of 61.62 g⊕ (604.29 m/s²), and an escape velocity of 302.9 km/s.
In its orbital architecture around HD 153557, HD 153557 d completes one full revolution every 40654.648 Earth days (111.31Julian years) at a semi-major axis of 21.449 AU (a wide outer-system orbit beyond Jupiter's 5.20 AU distance in our Solar System). Its mean orbital velocity is approximately 5.7 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.152 carries the world between 18.1888 AU at periapsis and 24.7092 AU at apoapsis, driving measurable seasonal insolation cycles.
❄️ Thermal Regime (Cryogenic Zone): With an equilibrium temperature of 43 K (-230°C / -382°F) and an incident flux of 0.00 S⊕ (~1 W/m²), surface water and volatile species on HD 153557 d would remain locked in cryogenic ice phases unless warmed by subsurface tidal or radiogenic heating.
The host star HD 153557 is classified as an orange K-type star of spectral type K0 with an effective photospheric temperature of 4,837 K, a radius of 0.7452 R☉, a mass of 0.79 M☉, an estimated bolometric luminosity of 0.273 L☉. From Earth, HD 153557 shines at apparent V-band magnitude 7.83 (accessible to binoculars and small amateur telescopes) in the Northern celestial hemisphere. The HD 153557 system is a multi-planet architecture hosting 3 confirmed worlds, with HD 153557 d sharing its stellar neighborhood alongside HD 153557 b, HD 153557 c.
Methodology: Computed using the Schulze-Makuch et al. (2011) weighted metric comparing physical interior (radius, estimated density) and surface thermal regime (escape velocity, equilibrium temperature).
Discovery Facility: Multiple Observatories · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | HD 153557 |
| Spectral Type | K0 |
| Effective Temp (Teff) | 4,837 K |
| Stellar Radius | 0.7452 R☉ |
| Stellar Mass | 0.7900 M☉ |
| Bolometric Luminosity | 0.273 L☉ |
| Metallicity [Fe/H] | — |
| Stellar Age | — |
| Apparent Magnitude | V: 7.830 · G: 7.505 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 21.449000 AU |
| Orbital Period | 40654.648 days |
| Mean Orbital Velocity | 5.7 km/s |
| Orbital Eccentricity (e) | 0.15200 |
| Orbital Inclination (i) | 14.3240° |
| Mean Bulk Density | 28.55 g/cm³ (302.9 km/s vesc) |
| Insolation Flux | 0.0006 S⊕ (~1 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 58.500 LY (17.941 pc) |