JWST atmosphere target
55 Cancri
Hosts 55 Cancri e — a lava world JWST detected silicate atmosphere on.
- Planets
- 7
- Distance
- 41.0 ly
- Host
- G-type
About 55 Cancri
Discovery
55 Cancri's planetary system was built up over decades — the inner planet 55 Cnc b was found in 1996 by Butler & Marcy via radial velocity, with planets c, d, e, and f confirmed between 2002 and 2007 around a naked-eye G8V star 41 light-years away.
Why it matters
55 Cancri e is one of the most bizarre worlds known: a 2 R⊕ super-Earth on an 18-hour orbit, with a dayside hot enough to vaporize rock. Its proximity and bright host make it the gold-standard target for lava-world atmospheres.
Current research
JWST NIRCam and MIRI observations in 2024 revealed strong day-side temperature variability and evidence for a substantial atmosphere — possibly outgassed silicate vapor rather than primordial hydrogen.
Comparable to
A super-Earth so close to its star that the dayside is a molten lava ocean — temperatures around 2,400 K, hot enough to melt iron.
System geometry
At a glance
- Hostname
- 55 Cnc
- Spectral type
- G8 V
- Distance
- 41.0 ly · 12.59 pc
- Stellar mass
- 0.91 M☉
- Stellar radius
- 0.94 R☉
- Luminosity
- 0.635 L☉
- Effective temp
- 5172 K
- Confirmed planets
- 7
- Habitable zone
- 0.757 – 1.092 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
5 confirmed (of 7 total in NASA archive).
Lava world
55 Cnc e
- Orbit
- 0.015 AU
- Period
- 0.74 days
- Radius
- 1.88 R⊕
- Mass
- 7.99 M⊕
- Eq. temperature
- 1958 K
- Eccentricity
- 0.050
- Discovered
- 2004 · Radial Velocity
Gas giant
55 Cnc b
- Orbit
- 0.118 AU
- Period
- 14.65 days
- Radius
- 13.90 R⊕
- Mass
- 263.98 M⊕
- Eq. temperature
- 700 K
- Eccentricity
- 0.003
- Discovered
- 1996 · Radial Velocity
Gas giant
55 Cnc c
- Orbit
- 0.247 AU
- Period
- 44.39 days
- Radius
- 8.51 R⊕
- Mass
- 54.47 M⊕
- Eq. temperature
- —
- Eccentricity
- 0.088
- Discovered
- 2004 · Radial Velocity
Gas giant
55 Cnc f
- Orbit
- 0.802 AU
- Period
- 260.58 days
- Radius
- 7.59 R⊕
- Mass
- 44.81 M⊕
- Eq. temperature
- —
- Eccentricity
- 0.063
- Discovered
- 2007 · Radial Velocity
Gas giant
55 Cnc d
- Orbit
- 5.600 AU
- Period
- 13.1 years
- Radius
- 13.00 R⊕
- Mass
- 1232.49 M⊕
- Eq. temperature
- —
- Eccentricity
- 0.091
- Discovered
- 2002 · Radial Velocity
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 |
|---|---|---|---|---|---|---|
| 55 Cnc e | 1.88 | 7.99 | 0.015 | 0.74 | 1958 | Earth |
| 55 Cnc b | 13.90 | 263.98 | 0.118 | 14.65 | 700 | Jupiter |
| 55 Cnc c | 8.51 | 54.47 | 0.247 | 44.39 | — | Saturn |
| 55 Cnc f | 7.59 | 44.81 | 0.802 | 260.58 | — | Saturn |
| 55 Cnc d | 13.00 | 1232.49 | 5.600 | 4799.00 | — | 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.
- 55 Cnc e
JWST programs include transit spectroscopy, thermal phase curves, and direct imaging coronagraph observations depending on planet class.
Discovery timeline
- 1996
55 Cnc b
via Radial Velocity
- 2002
55 Cnc d
via Radial Velocity
- 2004
2 planets: e, c
via Radial Velocity
- 2007
55 Cnc f
via Radial Velocity
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.
WASP-39
1 planets · 697.9 ly · G2V
JWST's first CO₂ detection in an exoplanet atmosphere (2022).
GJ 1214
1 planets · 47.8 ly · M4 V
A "steam world" — hot, volatile-rich super-Earth with a hazy atmosphere.
Related reading
Articles mentioning 55 Cancri:
Experience it
See 55 Cancri in interactive 3D
Fly through the system, click any planet, watch orbits play out at 100× speed.
▶ Launch 3D scene