Key parameters at a glance
- A radius of 12.22 Earth radii
- A mass of 721.47 Earth masses
- Surface gravity around 4.83 g
- An orbital period of 5.005 days
- Semi-major axis 0.0610 AU
- Equilibrium temperature 1,450 K (1177 °C)
- Distance from Earth 1,122.14 light-years
- Earth Similarity Index 0.109
- Travel time at Voyager 1 speed 19,788,933 years
HAT-P-31 b Planet Profile
Physical Specs
Classification
Planet Type
Gas Giant
Discovery
Size rank in cohort
Rank by radius
#1404of 1771
top 79.2%
This planet
12.22R⊕
Gas Giant median
13.52R⊕
Nearest-size peers
| Metric | Earth | HAT-P-31 b | Jupiter |
|---|---|---|---|
| Radius (R⊕) | 1.00 | 12.22 | 11.21 |
| Mass (M⊕) | 1.00 | 721.47 | 317.83 |
| Density (g/cm³) | 5.51 | 2.18 | 1.33 |
| Surface Gravity (g) | 1.00 | 4.83 | 2.53 |
| Insolation (S⊕) | 1.00 | 746.90 | 0.037 |
Alternative Mass Estimates
| Method | Value | Interpretation |
|---|---|---|
| Best measured mass | 721.474 M⊕ | Direct mass measurement (not derived). |
Star Catalogue Identifiers
TIC
TIC 320798691
Gaia DR2
Gaia DR2 4583004815239650176
Gaia DR3
Gaia DR3 4583004815239650176
System
HAT-P-31
Percentile among Gas Giant cohort
Orbit & Habitability
Orbital Dynamics
Year Length
A year here lasts approximately 5.01 Earth days (1.4% of a terrestrial year) on a mildly elliptical path at a mean orbital distance of 0.0610 AU.
Transit Fingerprint
Depth
0.650 %
Duration
4.906 h
Impact parameter b
0.723
Rp / R★
0.091300
Transit midpoint (BJD)
2,458,940.7533
Photometric dip
Transit produces a flux drop of 6,500 ppm lasting ≈ 4.91 h.
Extended Orbital Architecture
Planet / star radius ratio
0.091300
Semi-major axis / stellar radius
9.700
Impact parameter (b)
0.723
RV semi-amplitude (K)
232.500 m/s
Transit mid-time (BJD)
2,458,940.7533
Long. of periastron (ω)
276.30°
Angular separation (arcsec)
0.17700
Eq. Temperature
1,450K
(1177 °C)
Insolation (S⊕)
746.90
Earth = 1.00
Earth Similarity (ESI)
0.109
0 = alien, 1 = Earth-identical
Inside the inner HZ boundary (too hot for liquid water) — the dayside is scorched.
Detection Signatures
Transit photometry
A transit dip has been observed from at least one telescope.
Radial velocity
Stellar wobble has been measured spectroscopically.
Discovery Paper
Primary reference
Kipping et al. 2011Instrument
2K CCD Sensor
Publication
2011-09
Observation locale
Ground
Discovery cohort
Planets confirmed in 2011 at HATNet (10 shown).
Host System: HAT-P-31
Spectral Class
F-type yellow-white
Effective Temperature
6,065 K — hotter than the Sun (5,778 K)
Estimated Age
3.17 Gyr — younger than the Sun (4.6 Gyr)
Stellar Radius
1.390 R☉
Stellar Mass
1.310 M☉
Metallicity [Fe/H]
0.15
Extended Stellar Properties
Surface gravity (log g)
4.260 dex
Stellar density
0.690 g/cm³
Systemic radial velocity
-2.40 km/s
Rotational v·sin i
0.50 km/s
Metallicity ratio
[Fe/H]
Multi-band Host Photometry — 11 bands
Astrometric Data
Parallax
2.878 mas
Total Proper Motion
15.327 mas/yr
PM Right Ascension
-7.44 mas/yr
PM Declination
-13.40 mas/yr
Galactic Cartesian (pc)
x = 0.024 · y = -0.895 · z = 0.445
Equatorial (J2000)
RA 271.53767° · Dec 26.42661°
Galactic ℓ, b
52.720° · 21.063°
Ecliptic λ, β
272.132° · 49.854°
HTM-20 index
-1227415187
Similar Worlds
WASP-138 b
Gas Giant · F-type yellow-white
Radius 12.22 R⊕ · 1,351.0 ly
CoRoT-14 b
Gas Giant · F-type yellow-white
Radius 12.22 R⊕ · 5,690.1 ly
TOI-2145 b
Gas Giant · F-type yellow-white
Radius 12.24 R⊕ · 733.0 ly
TOI-2382 b
Gas Giant · F-type yellow-white
Radius 12.25 R⊕ · 1,418.5 ly
TOI-558 b
Gas Giant · F-type yellow-white
Radius 12.17 R⊕ · 1,313.2 ly
HATS-58 A b
Gas Giant · F-type yellow-white
Radius 12.27 R⊕ · 1,316.3 ly