Key parameters at a glance
- A radius of 12.00 Earth radii
- A mass of 7,668.56 Earth masses
- Surface gravity around 53.25 g
- An orbital period of 1,021.202 days
- Semi-major axis 3.2330 AU
- Distance from Earth 877.77 light-years
- Earth Similarity Index 0.269
- Travel time at Voyager 1 speed 15,479,484 years
1 sibling around HD 81817
HD 81817 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 81817 c | Gas Giant | 12.00 | 7,185.78 | 622.978 | — | 2022 |
| HD 81817 b this | Gas Giant | 12.00 | 7,668.56 | 1,021.202 | — | 2020 |
HD 81817 b Planet Profile
Physical Specs
Classification
Planet Type
Gas Giant
Discovery
Size rank in cohort
Rank by radius
#1494of 1771
top 84.3%
This planet
12.00R⊕
Gas Giant median
13.52R⊕
Nearest-size peers
| Metric | Earth | HD 81817 b | Jupiter |
|---|---|---|---|
| Radius (R⊕) | 1.00 | 12.00 | 11.21 |
| Mass (M⊕) | 1.00 | 7,668.56 | 317.83 |
| Density (g/cm³) | 5.51 | 24.40 | 1.33 |
| Surface Gravity (g) | 1.00 | 53.25 | 2.53 |
| Insolation (S⊕) | 1.00 | — | 0.037 |
Alternative Mass Estimates
| Method | Value | Interpretation |
|---|---|---|
| Best measured mass | 7,668.564 M⊕ | Direct mass measurement (not derived). |
| Minimum mass (M sin i) | 8,613.193 M⊕ | Lower bound from radial-velocity fitting. |
Star Catalogue Identifiers
HD
HD 81817
HIP
HIP 47193
TIC
TIC 137603530
Gaia DR2
Gaia DR2 1144716265940854016
Gaia DR3
Gaia DR3 1144716265942885888
System
HD 81817
Percentile among Gas Giant cohort
Orbit & Habitability
Orbital Dynamics
Year Length
A year here lasts about 2.80 Earth years on a nearly circular orbit at a mean orbital distance of 3.2330 AU.
Eq. Temperature
—
Insolation (S⊕)
—
Earth = 1.00
Earth Similarity (ESI)
0.269
0 = alien, 1 = Earth-identical
Discovery Paper
Primary reference
Bang et al. 2020Instrument
BOES Echelle Spectrograph
Publication
2020-06
Observation locale
Ground
Discovery cohort
Planets confirmed in 2020 at Bohyunsan Optical Astronomical Observatory (2 shown).
Host System: HD 81817
Spectral Class
K-type orange
Effective Temperature
4,140 K — cooler than the Sun (5,778 K)
Estimated Age
0.15 Gyr — younger than the Sun (4.6 Gyr)
Stellar Radius
83.800 R☉
Stellar Mass
4.300 M☉
Metallicity [Fe/H]
-0.17
Extended Stellar Properties
Surface gravity (log g)
1.300 dex
Rotational v·sin i
4.70 km/s
Metallicity ratio
[Fe/H]
Multi-band Host Photometry — 11 bands
Astrometric Data
Parallax
3.718 mas
Total Proper Motion
24.331 mas/yr
PM Right Ascension
-16.79 mas/yr
PM Declination
-17.61 mas/yr
Galactic Cartesian (pc)
x = -0.122 · y = 0.088 · z = 0.989
Equatorial (J2000)
RA 144.27157° · Dec 81.32631°
Galactic ℓ, b
130.652° · 32.653°
Ecliptic λ, β
104.477° · 60.687°
HTM-20 index
1161563939
Similar Worlds
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Radius 12.00 R⊕ · 399.1 ly
nu Oph b
Gas Giant · K-type orange
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nu Oph c
Gas Giant · K-type orange
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GJ 680 b
Gas Giant · K-type orange
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HD 81817 c
Gas Giant · K-type orange
Radius 12.00 R⊕ · 877.8 ly
HAT-P-68 b
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Radius 12.02 R⊕ · 659.3 ly