Key parameters at a glance
- A radius of 12.26 Earth radii
- A mass of 1,036.12 Earth masses
- Surface gravity around 6.89 g
- An orbital period of 21.216 days
- Semi-major axis 0.1632 AU
- Equilibrium temperature 888 K (615 °C)
- Distance from Earth 254.68 light-years
- Earth Similarity Index 0.194
- Travel time at Voyager 1 speed 4,491,337 years
HD 17156 b Planet Profile
Physical Specs
Classification
Planet Type
Gas Giant
Discovery
Size rank in cohort
Rank by radius
#1394of 1771
top 78.7%
This planet
12.26R⊕
Gas Giant median
13.52R⊕
Nearest-size peers
| Metric | Earth | HD 17156 b | Jupiter |
|---|---|---|---|
| Radius (R⊕) | 1.00 | 12.26 | 11.21 |
| Mass (M⊕) | 1.00 | 1,036.12 | 317.83 |
| Density (g/cm³) | 5.51 | 3.08 | 1.33 |
| Surface Gravity (g) | 1.00 | 6.89 | 2.53 |
| Insolation (S⊕) | 1.00 | 68.80 | 0.037 |
Alternative Mass Estimates
| Method | Value | Interpretation |
|---|---|---|
| Best measured mass | 1,036.121 M⊕ | Direct mass measurement (not derived). |
| Minimum mass (M sin i) | 1,036.121 M⊕ | Lower bound from radial-velocity fitting. |
Star Catalogue Identifiers
HD
HD 17156
HIP
HIP 13192
TIC
TIC 302773669
Gaia DR2
Gaia DR2 545560867790611072
Gaia DR3
Gaia DR3 545560867790611072
System
HD 17156
Percentile among Gas Giant cohort
Orbit & Habitability
Orbital Dynamics
Year Length
A year here lasts approximately 21.22 Earth days (5.8% of a terrestrial year) on a highly eccentric trajectory at a mean orbital distance of 0.1632 AU.
Transit Fingerprint
Depth
0.549 %
Duration
3.151 h
Impact parameter b
0.484
Rp / R★
0.074120
Transit midpoint (BJD)
2,458,809.0704
Photometric dip
Transit produces a flux drop of 5,493 ppm lasting ≈ 3.15 h.
Extended Orbital Architecture
Planet / star radius ratio
0.074120
Semi-major axis / stellar radius
23.110
Impact parameter (b)
0.484
RV semi-amplitude (K)
274.500 m/s
Transit mid-time (BJD)
2,458,809.0704
Long. of periastron (ω)
122.06°
Sky-projected obliquity (λ)
-4.80°
Angular separation (arcsec)
2.09000
Eq. Temperature
888K
(615 °C)
Insolation (S⊕)
68.80
Earth = 1.00
Earth Similarity (ESI)
0.194
0 = alien, 1 = Earth-identical
Inside the inner HZ boundary (too hot for liquid water) — the surface is too hot to retain surface water.
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
Fischer et al. 2007Instrument
HDS Spectrograph
Publication
2007-11
Observation locale
Ground
Host System: HD 17156
Spectral Class
G-type yellow (Sun-like)
Effective Temperature
6,046 K — hotter than the Sun (5,778 K)
Estimated Age
3.30 Gyr — younger than the Sun (4.6 Gyr)
Stellar Radius
1.517 R☉
Stellar Mass
1.285 M☉
Metallicity [Fe/H]
0.21
Extended Stellar Properties
Surface gravity (log g)
4.184 dex
Stellar density
0.517 g/cm³
Systemic radial velocity
-3.22 km/s
Rotational v·sin i
2.80 km/s
Rotation period
12.80 days
Metallicity ratio
[Fe/H]
Multi-band Host Photometry — 11 bands
Astrometric Data
Parallax
12.778 mas
Total Proper Motion
96.849 mas/yr
PM Right Ascension
90.98 mas/yr
PM Declination
-33.20 mas/yr
Galactic Cartesian (pc)
x = 0.231 · y = 0.211 · z = 0.950
Equatorial (J2000)
RA 42.43661° · Dec 71.75309°
Galactic ℓ, b
131.990° · 10.994°
Ecliptic λ, β
67.985° · 51.934°
HTM-20 index
483043669
Observation Record
Photometric series
27
RV measurements
8
Stellar spectra
1
Archive notes
1
Similar Worlds
TOI-3976 A b
Gas Giant · G-type yellow (Sun-like)
Radius 12.27 R⊕ · 1,683.2 ly
Qatar-3 b
Gas Giant · G-type yellow (Sun-like)
Radius 12.29 R⊕ · 2,399.2 ly
WASP-170 b
Gas Giant · G-type yellow (Sun-like)
Radius 12.29 R⊕ · 996.7 ly
TOI-559 b
Gas Giant · G-type yellow (Sun-like)
Radius 12.23 R⊕ · 760.8 ly
TOI-3364 b
Gas Giant · G-type yellow (Sun-like)
Radius 12.23 R⊕ · 906.4 ly
Kepler-30 c
Gas Giant · G-type yellow (Sun-like)
Radius 12.30 R⊕ · 2,981.8 ly