JWST atmosphere target
WASP-39
JWST's first CO₂ detection in an exoplanet atmosphere (2022).
- Planets
- 1
- Distance
- 697.9 ly
- Host
- G-type
About WASP-39
Discovery
WASP-39 b was discovered in 2011 by the SuperWASP transit survey (Faedi et al.), an inflated Saturn-mass gas giant on a 4-day orbit around a Sun-like late-G star.
Why it matters
In 2022 WASP-39 b became the first exoplanet with carbon dioxide unambiguously detected in its atmosphere — a flagship JWST early-release result. Subsequent JWST data also yielded the first exoplanet detection of sulfur dioxide, a photochemistry signature.
Current research
WASP-39 b remains the most thoroughly characterized hot-Jupiter atmosphere; JWST follow-up continues across NIRSpec, NIRCam, NIRISS, and MIRI to build a complete molecular inventory.
Comparable to
A puffy, hot version of Saturn — roughly Saturn's mass but inflated to nearly Jupiter's size by the heat of its parent star.
System geometry
At a glance
- Hostname
- WASP-39
- Spectral type
- G2V
- Distance
- 697.9 ly · 213.98 pc
- Stellar mass
- 0.91 M☉
- Stellar radius
- 0.94 R☉
- Luminosity
- 0.745 L☉
- Effective temp
- 5485 K
- Confirmed planets
- 1
- Habitable zone
- 0.820 – 1.182 AU
Top-down orbital diagram
Orbits to scale within this system. Dashed green = habitable-zone edges.
Planet positions are illustrative (evenly spaced in phase). For live motion see the 3D scene.
The planets
1 confirmed.
Gas giant
WASP-39 b
- Orbit
- 0.048 AU
- Period
- 4.06 days
- Radius
- 14.34 R⊕
- Mass
- 89.31 M⊕
- Eq. temperature
- 1166 K
- Eccentricity
- 0.000
- Discovered
- 2011 · Transit
Compared to our Solar System
Each row shows the closest Solar-System analog by radius (log-space). Earth is pinned at the bottom as the constant frame of reference.
| Planet | Radius (R⊕) | Mass (M⊕) | Orbit (AU) | Period (days) | Eq temp (K) | Solar analog |
|---|---|---|---|---|---|---|
| WASP-39 b | 14.34 | 89.31 | 0.048 | 4.06 | 1166 | Jupiter |
| Earth (reference) | 1.00 | 1.00 | 1.000 | 365.25 | 255 | — |
Research status
◇ JWST observation status
1 planet has confirmed JWST observation time across Cycles 1–3.
- WASP-39 b
JWST programs include transit spectroscopy, thermal phase curves, and direct imaging coronagraph observations depending on planet class.
Discovery timeline
- 2011
WASP-39 b
via Transit
If you liked this
Other systems in the same theme:
K2-18
2 planets · 124.0 ly · M2.5 V
JWST detected possible dimethyl sulfide — a potential biosignature, still debated.
GJ 1214
1 planets · 47.8 ly · M4 V
A "steam world" — hot, volatile-rich super-Earth with a hazy atmosphere.
55 Cancri
5 planets · 41.0 ly · G8 V
Hosts 55 Cancri e — a lava world JWST detected silicate atmosphere on.
Experience it
See WASP-39 in interactive 3D
Fly through the system, click any planet, watch orbits play out at 100× speed.
▶ Launch 3D scene