Key parameters at a glance
- A radius of 13.90 Earth radii
- A mass of 3,241.85 Earth masses
- Surface gravity around 16.78 g
- An orbital period of 0.941 days
- Semi-major axis 0.0202 AU
- Equilibrium temperature 2,429 K (2156 °C)
- Distance from Earth 402.75 light-years
- Earth Similarity Index 0.058
- Travel time at Voyager 1 speed 7,102,447 years
WASP-18 b Planet Profile
Physical Specs
Classification
Planet Type
Gas Giant
Discovery
Size rank in cohort
Rank by radius
#504of 1771
top 28.4%
This planet
13.90R⊕
Gas Giant median
13.52R⊕
Nearest-size peers
| Metric | Earth | WASP-18 b | Jupiter |
|---|---|---|---|
| Radius (R⊕) | 1.00 | 13.90 | 11.21 |
| Mass (M⊕) | 1.00 | 3,241.85 | 317.83 |
| Density (g/cm³) | 5.51 | 6.60 | 1.33 |
| Surface Gravity (g) | 1.00 | 16.78 | 2.53 |
| Insolation (S⊕) | 1.00 | 5,805.00 | 0.037 |
Alternative Mass Estimates
| Method | Value | Interpretation |
|---|---|---|
| Best measured mass | 3,241.850 M⊕ | Direct mass measurement (not derived). |
| Minimum mass (M sin i) | 3,222.780 M⊕ | Lower bound from radial-velocity fitting. |
Star Catalogue Identifiers
HD
HD 10069
HIP
HIP 7562
TIC
TIC 100100827
Gaia DR2
Gaia DR2 4955371367334610048
Gaia DR3
Gaia DR3 4955371367334610048
System
WASP-18
Percentile among Gas Giant cohort
Orbit & Habitability
Orbital Dynamics
Year Length
A year here lasts roughly 22.6 hours long on a nearly circular orbit at a mean orbital distance of 0.0202 AU.
Transit Fingerprint
Depth
1.041 %
Duration
2.210 h
Impact parameter b
0.360
Rp / R★
0.101800
Transit midpoint (BJD)
2,456,740.8056
Photometric dip
Transit produces a flux drop of 10,410 ppm lasting ≈ 2.21 h.
Extended Orbital Architecture
Planet / star radius ratio
0.101800
Semi-major axis / stellar radius
3.480
Impact parameter (b)
0.360
RV semi-amplitude (K)
1,814.000 m/s
Occultation depth
0.034 ppm
Transit mid-time (BJD)
2,456,740.8056
Long. of periastron (ω)
-85.00°
Sky-projected obliquity (λ)
4.00°
Angular separation (arcsec)
0.16400
Eq. Temperature
2,429K
(2156 °C)
Insolation (S⊕)
5,805.00
Earth = 1.00
Earth Similarity (ESI)
0.058
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.
Transit timing variations
Gravitational interactions from neighbours have been detected.
Orbital-brightness modulation
Host star brightness varies with the planet's orbit.
Discovery Paper
Primary reference
Hellier et al. 2009Instrument
iKon-L CCD Camera
Publication
2009-08
Observation locale
Ground
Discovery cohort
Planets confirmed in 2009 at SuperWASP (6 shown).
Host System: WASP-18
Spectral Class
F-type yellow-white
Effective Temperature
6,432 K — hotter than the Sun (5,778 K)
Estimated Age
1.57 Gyr — younger than the Sun (4.6 Gyr)
Stellar Radius
1.319 R☉
Stellar Mass
1.294 M☉
Metallicity [Fe/H]
0.11
Extended Stellar Properties
Surface gravity (log g)
4.310 dex
Stellar density
0.795 g/cm³
Systemic radial velocity
3.20 km/s
Rotational v·sin i
11.00 km/s
Metallicity ratio
[Fe/H]
Multi-band Host Photometry — 11 bands
Astrometric Data
Parallax
8.069 mas
Total Proper Motion
32.580 mas/yr
PM Right Ascension
25.24 mas/yr
PM Declination
20.60 mas/yr
Galactic Cartesian (pc)
x = 0.637 · y = 0.288 · z = -0.715
Equatorial (J2000)
RA 24.35446° · Dec -45.67779°
Galactic ℓ, b
279.710° · -69.321°
Ecliptic λ, β
358.176° · -50.444°
HTM-20 index
1537412788
Observation Record
Photometric series
8
Transmission spectra
2
Emission spectra
31
Archive notes
4
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