Teegarden's Star d
Astrophysical Synthesis & Habitability Characterization
Teegarden's Star d is a confirmed terrestrial exoplanet orbiting the star Teegarden's Star, located approximately 12.5 light-years (3.83 parsecs) from the Solar System. First announced in 2024 by Multiple Observatories using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 0.954 Earth radii and has a measured mass of 0.82 Earth masses. Combining its mass and radius yields a mean bulk density of 5.21 g/cm³ (a terrestrial silicate-iron composition comparable to Earth (5.51 g/cm³)), a surface gravity of 0.9 g⊕ (8.83 m/s²), and an escape velocity of 10.4 km/s.
In its orbital architecture around Teegarden's Star, Teegarden's Star d completes one full revolution every 26.13 Earth days at a semi-major axis of 0.0791 AU (orbiting interior to Mercury's 0.387 AU benchmark in the Solar System). Its mean orbital velocity is approximately 32.9 km/s (compared to Earth's 29.8 km/s). Its moderate orbital eccentricity of e = 0.07 carries the world between 0.0736 AU at periapsis and 0.0846 AU at apoapsis, driving measurable seasonal insolation cycles.
❄️ Thermal Regime (Cryogenic Zone): With an equilibrium temperature of 159 K (-114°C / -173°F) and an incident flux of 0.12 S⊕ (~163 W/m²), surface water and volatile species on Teegarden's Star d would remain locked in cryogenic ice phases unless warmed by subsurface tidal or radiogenic heating.
The host star Teegarden's Star is classified as a low-mass red dwarf of spectral type M7.0 V with an effective photospheric temperature of 3,034 K, a radius of 0.12 R☉, a mass of 0.097 M☉, an estimated bolometric luminosity of 0.00109 L☉. Stellar evolution modeling indicates an estimated stellar age of 8 Gyr and a metallicity of [Fe/H] = -0.11 dex (metal-poor relative to the Sun). From Earth, Teegarden's Star shines at apparent V-band magnitude 15.13 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The Teegarden's Star system is a multi-planet architecture hosting 3 confirmed worlds, with Teegarden's Star d sharing its stellar neighborhood alongside Teegarden's Star b, Teegarden's Star 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 | Teegarden's Star |
| Spectral Type | M7.0 V |
| Effective Temp (Teff) | 3,034 K |
| Stellar Radius | 0.1200 R☉ |
| Stellar Mass | 0.0970 M☉ |
| Bolometric Luminosity | 0.00109 L☉ |
| Metallicity [Fe/H] | -0.110 dex |
| Stellar Age | 8.000 Gyr |
| Apparent Magnitude | V: 15.130 · G: 12.275 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 0.079100 AU |
| Orbital Period | 26.13 days |
| Mean Orbital Velocity | 32.9 km/s |
| Orbital Eccentricity (e) | 0.07000 |
| Orbital Inclination (i) | — |
| Mean Bulk Density | 5.21 g/cm³ (10.4 km/s vesc) |
| Insolation Flux | 0.1200 S⊕ (~163 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 12.500 LY (3.831 pc) |