Key parameters at a glance
- A radius of 12.58 Earth radii
- A mass of 167.50 Earth masses
- Surface gravity around 1.06 g
- An orbital period of 4.982 days
- Semi-major axis 0.0561 AU
- Equilibrium temperature 1,021 K (748 °C)
- Distance from Earth 578.25 light-years
- Earth Similarity Index 0.127
- Travel time at Voyager 1 speed 10,197,354 years
WASP-42 b Planet Profile
Physical Specs
Classification
Planet Type
Gas Giant
Discovery
Size rank in cohort
Rank by radius
#1225of 1771
top 69.1%
This planet
12.58R⊕
Gas Giant median
13.52R⊕
Nearest-size peers
| Metric | Earth | WASP-42 b | Jupiter |
|---|---|---|---|
| Radius (R⊕) | 1.00 | 12.58 | 11.21 |
| Mass (M⊕) | 1.00 | 167.50 | 317.83 |
| Density (g/cm³) | 5.51 | 0.46 | 1.33 |
| Surface Gravity (g) | 1.00 | 1.06 | 2.53 |
| Insolation (S⊕) | 1.00 | 137.12 | 0.037 |
Alternative Mass Estimates
| Method | Value | Interpretation |
|---|---|---|
| Best measured mass | 167.496 M⊕ | Direct mass measurement (not derived). |
Star Catalogue Identifiers
TIC
TIC 248075138
Gaia DR2
Gaia DR2 6139698733664726784
Gaia DR3
Gaia DR3 6139698733664726784
System
WASP-42
Percentile among Gas Giant cohort
Orbit & Habitability
Orbital Dynamics
Year Length
A year here lasts approximately 4.98 Earth days (1.4% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0561 AU.
Transit Fingerprint
Depth
1.811 %
Duration
2.890 h
Impact parameter b
0.457
Rp / R★
0.129300
Transit midpoint (BJD)
2,455,650.5673
Photometric dip
Transit produces a flux drop of 18,110 ppm lasting ≈ 2.89 h.
Extended Orbital Architecture
Planet / star radius ratio
0.129300
Semi-major axis / stellar radius
13.500
Impact parameter (b)
0.457
RV semi-amplitude (K)
64.800 m/s
Transit mid-time (BJD)
2,455,650.5673
Long. of periastron (ω)
159.00°
Angular separation (arcsec)
0.31600
Eq. Temperature
1,021K
(748 °C)
Insolation (S⊕)
137.12
Earth = 1.00
Earth Similarity (ESI)
0.127
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
Lendl et al. 2012Instrument
iKon-L CCD Camera
Publication
2012-08
Observation locale
Ground
Discovery cohort
Planets confirmed in 2012 at SuperWASP (12 shown).
Host System: WASP-42
Spectral Class
G-type yellow (Sun-like)
Effective Temperature
5,315 K — cooler than the Sun (5,778 K)
Estimated Age
4.40 Gyr — younger than the Sun (4.6 Gyr)
Stellar Radius
0.892 R☉
Stellar Mass
0.951 M☉
Metallicity [Fe/H]
0.29
Extended Stellar Properties
Surface gravity (log g)
4.515 dex
Stellar density
1.885 g/cm³
Systemic radial velocity
-3.74 km/s
Rotational v·sin i
2.70 km/s
Metallicity ratio
[Fe/H]
Multi-band Host Photometry — 11 bands
Astrometric Data
Parallax
5.612 mas
Total Proper Motion
50.018 mas/yr
PM Right Ascension
-49.78 mas/yr
PM Declination
4.87 mas/yr
Galactic Cartesian (pc)
x = -0.723 · y = -0.167 · z = -0.670
Equatorial (J2000)
RA 192.98120° · Dec -42.07362°
Galactic ℓ, b
303.029° · 20.798°
Ecliptic λ, β
210.110° · -33.262°
HTM-20 index
-1597810276
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