Key parameters at a glance
- A radius of 19.53 Earth radii
- A mass of 371.86 Earth masses
- Surface gravity around 0.98 g
- An orbital period of 1.275 days
- Semi-major axis 0.0257 AU
- Equilibrium temperature 2,409 K (2136 °C)
- Distance from Earth 880.29 light-years
- Earth Similarity Index 0.037
- Travel time at Voyager 1 speed 15,523,887 years
WASP-121 b Planet Profile
Physical Specs
Classification
Planet Type
Gas Giant
Discovery
Size rank in cohort
Rank by radius
#37of 1771
top 2.0%
This planet
19.53R⊕
Gas Giant median
13.52R⊕
Nearest-size peers
| Metric | Earth | WASP-121 b | Jupiter |
|---|---|---|---|
| Radius (R⊕) | 1.00 | 19.53 | 11.21 |
| Mass (M⊕) | 1.00 | 371.86 | 317.83 |
| Density (g/cm³) | 5.51 | 0.28 | 1.33 |
| Surface Gravity (g) | 1.00 | 0.98 | 2.53 |
| Insolation (S⊕) | 1.00 | 6,216.41 | 0.037 |
Alternative Mass Estimates
| Method | Value | Interpretation |
|---|---|---|
| Best measured mass | 371.859 M⊕ | Direct mass measurement (not derived). |
Star Catalogue Identifiers
TIC
TIC 22529346
Gaia DR2
Gaia DR2 5565050255701441664
Gaia DR3
Gaia DR3 5565050255701441664
System
WASP-121
Percentile among Gas Giant cohort
Orbit & Habitability
Orbital Dynamics
Year Length
A year here lasts approximately 1.27 Earth days (0.3% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0257 AU.
Transit Fingerprint
Depth
1.502 %
Duration
2.905 h
Impact parameter b
0.100
Rp / R★
0.122551
Transit midpoint (BJD)
2,458,661.5638
Photometric dip
Transit produces a flux drop of 15,018 ppm lasting ≈ 2.91 h.
Extended Orbital Architecture
Planet / star radius ratio
0.122551
Semi-major axis / stellar radius
3.784
Impact parameter (b)
0.100
RV semi-amplitude (K)
181.100 m/s
Occultation depth
0.113 ppm
Transit mid-time (BJD)
2,458,661.5638
Long. of periastron (ω)
10.00°
Sky-projected obliquity (λ)
87.20°
Angular separation (arcsec)
0.09530
Eq. Temperature
2,409K
(2136 °C)
Insolation (S⊕)
6,216.41
Earth = 1.00
Earth Similarity (ESI)
0.037
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
Delrez et al. 2016Instrument
e2v CCD Camera
Publication
2016-06
Observation locale
Ground
Discovery cohort
Planets confirmed in 2016 at SuperWASP (11 shown).
Host System: WASP-121
Spectral Class
F-type yellow-white
Effective Temperature
6,628 K — hotter than the Sun (5,778 K)
Estimated Age
1.11 Gyr — younger than the Sun (4.6 Gyr)
Stellar Radius
1.461 R☉
Stellar Mass
1.330 M☉
Metallicity [Fe/H]
0.17
Extended Stellar Properties
Surface gravity (log g)
4.251 dex
Stellar density
0.631 g/cm³
Systemic radial velocity
38.35 km/s
Rotational v·sin i
13.50 km/s
Rotation period
1.13 days
Metallicity ratio
[Fe/H]
Multi-band Host Photometry — 11 bands
Astrometric Data
Parallax
3.676 mas
Total Proper Motion
25.894 mas/yr
PM Right Ascension
-3.85 mas/yr
PM Declination
25.61 mas/yr
Galactic Cartesian (pc)
x = -0.235 · y = 0.740 · z = -0.631
Equatorial (J2000)
RA 107.60023° · Dec -39.09727°
Galactic ℓ, b
250.294° · -13.325°
Ecliptic λ, β
118.740° · -60.792°
HTM-20 index
-327295076
Similar Worlds
KELT-15 b
Gas Giant · F-type yellow-white
Radius 19.50 R⊕ · 1,059.0 ly
HATS-26 b
Gas Giant · F-type yellow-white
Radius 19.62 R⊕ · 2,811.0 ly
TOI-640 b
Gas Giant · F-type yellow-white
Radius 19.28 R⊕ · 1,115.4 ly
KELT-12 b
Gas Giant · F-type yellow-white
Radius 19.95 R⊕ · 1,200.4 ly
HAT-P-64 b
Gas Giant · F-type yellow-white
Radius 19.09 R⊕ · 2,126.2 ly
Qatar-7 b
Gas Giant · F-type yellow-white
Radius 19.06 R⊕ · 2,302.6 ly