Key parameters at a glance
- A radius of 0.96 Earth radii
- A mass of 0.83 Earth masses
- Surface gravity around 0.90 g
- An orbital period of 4.466 days
- Semi-major axis 0.0460 AU
- Equilibrium temperature 834 K (561 °C)
- Distance from Earth 41.68 light-years
- Earth Similarity Index 0.388
- Travel time at Voyager 1 speed 734,966 years
- Almost certainly tidally locked to its host star given the close orbit
1 sibling around HIP 56998
HD 101581 b shares its host star with 1 other confirmed planet. Side-by-side measurements below.
| Planet | Type | Radius (R⊕) | Mass (M⊕) | Period (d) | Eq. T (K) | Year |
|---|---|---|---|---|---|---|
| HD 101581 b this | Rocky Terrestrial | 0.96 | 0.83 | 4.466 | 834 | 2025 |
| HD 101581 c | Rocky Terrestrial | 0.99 | 0.94 | 6.204 | 747 | 2025 |
HD 101581 b Planet Profile
Physical Specs
Classification
Planet Type
Rocky Terrestrial
Discovery
Size rank in cohort
Rank by radius
#372of 570
top 65.1%
This planet
0.96R⊕
Rocky Terrestrial median
1.01R⊕
Nearest-size peers
| Metric | Earth | HD 101581 b | Jupiter |
|---|---|---|---|
| Radius (R⊕) | 1.00 | 0.96 | 11.21 |
| Mass (M⊕) | 1.00 | 0.83 | 317.83 |
| Density (g/cm³) | 5.51 | 5.20 | 1.33 |
| Surface Gravity (g) | 1.00 | 0.90 | 2.53 |
| Insolation (S⊕) | 1.00 | 80.00 | 0.037 |
Star Catalogue Identifiers
HD
HD 101581
HIP
HIP 56998
TIC
TIC 397362481
Gaia DR2
Gaia DR2 5378886891122066560
Gaia DR3
Gaia DR3 5378886891123024512
System
HIP 56998
Percentile among Rocky Terrestrial cohort
Orbit & Habitability
Orbital Dynamics
Year Length
A year here lasts approximately 4.47 Earth days (1.2% of a terrestrial year) at a mean orbital distance of 0.0460 AU.
Transit Fingerprint
Depth
0.021 %
Duration
1.770 h
Impact parameter b
0.616
Rp / R★
0.013900
Transit midpoint (BJD)
2,460,014.8496
Photometric dip
Transit produces a flux drop of 211 ppm lasting ≈ 1.77 h.
Extended Orbital Architecture
Planet / star radius ratio
0.013900
Impact parameter (b)
0.616
Transit mid-time (BJD)
2,460,014.8496
Angular separation (arcsec)
3.60000
Eq. Temperature
834K
(561 °C)
Insolation (S⊕)
80.00
Earth = 1.00
Earth Similarity (ESI)
0.388
0 = alien, 1 = Earth-identical
Inside the inner HZ boundary (too hot for liquid water) — the surface is too hot to retain surface water. Close-orbiting tidally-locked around a cool host.
Discovery Paper
Primary reference
Kunimoto et al. 2025Instrument
TESS CCD Array
Publication
2025-01
Observation locale
Space
Discovery cohort
Planets confirmed in 2025 at Transiting Exoplanet Survey Satellite (TESS) (12 shown).
Host System: HIP 56998
Spectral Class
K-type orange
Effective Temperature
4,675 K — cooler than the Sun (5,778 K)
Estimated Age
6.88 Gyr — older than the Sun (4.6 Gyr)
Stellar Radius
0.630 R☉
Stellar Mass
0.653 M☉
Metallicity [Fe/H]
-0.34
Extended Stellar Properties
Surface gravity (log g)
4.654 dex
Stellar density
4.158 g/cm³
Systemic radial velocity
12.90 km/s
Rotational v·sin i
2.47 km/s
Metallicity ratio
[Fe/H]
Multi-band Host Photometry — 8 bands
Astrometric Data
Parallax
78.230 mas
Total Proper Motion
703.291 mas/yr
PM Right Ascension
-660.42 mas/yr
PM Declination
241.80 mas/yr
Galactic Cartesian (pc)
x = -0.712 · y = 0.059 · z = -0.700
Equatorial (J2000)
RA 175.25630° · Dec -44.40415°
Galactic ℓ, b
289.897° · 16.678°
Ecliptic λ, β
197.470° · -41.719°
HTM-20 index
-345402495
Similar Worlds
EPIC 206317286 b
Rocky Terrestrial · K-type orange
Radius 0.96 R⊕ · 1,025.3 ly
Kepler-1049 b
Rocky Terrestrial · K-type orange
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Kepler-1957 b
Rocky Terrestrial · K-type orange
Radius 0.94 R⊕ · 1,503.2 ly
Kepler-1053 b
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Radius 0.98 R⊕ · 492.9 ly
Kepler-220 d
Rocky Terrestrial · K-type orange
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Kepler-398 b
Rocky Terrestrial · K-type orange
Radius 0.93 R⊕ · 578.5 ly