Key parameters at a glance
- A radius of 9.72 Earth radii
- A mass of 2,302.90 Earth masses
- Surface gravity around 24.38 g
- An orbital period of 2.875 days
- Semi-major axis 0.0361 AU
- Equilibrium temperature 970 K (697 °C)
- Distance from Earth 231.69 light-years
- Earth Similarity Index 0.158
- Travel time at Voyager 1 speed 4,085,901 years
- Almost certainly tidally locked to its host star given the close orbit
HAT-P-20 b Planet Profile
Physical Specs
Classification
Planet Type
Neptune-like
Discovery
Size rank in cohort
Rank by radius
#23of 574
top 3.8%
This planet
9.72R⊕
Neptune-like median
6.39R⊕
Nearest-size peers
| Metric | Earth | HAT-P-20 b | Jupiter |
|---|---|---|---|
| Radius (R⊕) | 1.00 | 9.72 | 11.21 |
| Mass (M⊕) | 1.00 | 2,302.90 | 317.83 |
| Density (g/cm³) | 5.51 | 13.78 | 1.33 |
| Surface Gravity (g) | 1.00 | 24.38 | 2.53 |
| Insolation (S⊕) | 1.00 | 85.12 | 0.037 |
Alternative Mass Estimates
| Method | Value | Interpretation |
|---|---|---|
| Best measured mass | 2,302.899 M⊕ | Direct mass measurement (not derived). |
Star Catalogue Identifiers
TIC
TIC 26826078
Gaia DR2
Gaia DR2 869913435026514688
Gaia DR3
Gaia DR3 869913435026514688
System
HAT-P-20
Percentile among Neptune-like cohort
Orbit & Habitability
Orbital Dynamics
Year Length
A year here lasts approximately 2.88 Earth days (0.8% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0361 AU.
Transit Fingerprint
Depth
0.990 %
Duration
1.848 h
Impact parameter b
0.631
Rp / R★
0.128400
Transit midpoint (BJD)
2,455,080.9266
Photometric dip
Transit produces a flux drop of 9,898 ppm lasting ≈ 1.85 h.
Extended Orbital Architecture
Planet / star radius ratio
0.128400
Semi-major axis / stellar radius
11.170
Impact parameter (b)
0.631
RV semi-amplitude (K)
1,246.000 m/s
Transit mid-time (BJD)
2,455,080.9266
Long. of periastron (ω)
317.00°
Sky-projected obliquity (λ)
-8.00°
True obliquity (ψ)
36.00°
Angular separation (arcsec)
0.50800
Eq. Temperature
970K
(697 °C)
Insolation (S⊕)
85.12
Earth = 1.00
Earth Similarity (ESI)
0.158
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.
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
Bakos et al. 2010Instrument
2K CCD Sensor
Publication
2011-12
Observation locale
Ground
Discovery cohort
Planets confirmed in 2010 at HATNet (12 shown).
Host System: HAT-P-20
Spectral Class
K-type orange
Effective Temperature
4,595 K — cooler than the Sun (5,778 K)
Estimated Age
6.70 Gyr — older than the Sun (4.6 Gyr)
Stellar Radius
0.694 R☉
Stellar Mass
0.756 M☉
Metallicity [Fe/H]
0.35
Extended Stellar Properties
Surface gravity (log g)
4.630 dex
Stellar density
2.360 g/cm³
Systemic radial velocity
-18.81 km/s
Rotational v·sin i
2.10 km/s
Rotation period
14.48 days
Metallicity ratio
[Fe/H]
Multi-band Host Photometry — 16 bands
Astrometric Data
Parallax
14.048 mas
Total Proper Motion
96.364 mas/yr
PM Right Ascension
-4.99 mas/yr
PM Declination
-96.23 mas/yr
Galactic Cartesian (pc)
x = -0.340 · y = 0.845 · z = 0.412
Equatorial (J2000)
RA 111.91643° · Dec 24.33612°
Galactic ℓ, b
194.415° · 18.394°
Ecliptic λ, β
109.897° · 2.398°
HTM-20 index
-1680301914
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