55 Cnc planetary system
55 Cnc is a Sun-like main-sequence star of spectral type G8 V approximately 41.0 light-years from Earth (12.59 parsecs). It hosts 5 confirmed exoplanets. 1 planet transits the host star from our line of sight, allowing direct measurements of size and atmosphere.
Host star
- Name
- 55 Cnc
- Spectral type
- G8 V
- Effective temperature
- 5,172 K
- Mass
- 0.91 M☉ (solar masses)
- Radius
- 0.94 R☉ (solar radii)
- Distance
- 12.59 pc (41.0 ly)
- Hipparcos catalog
- HIP 43587
Confirmed planets (5)
| Planet | Class | Mass (M⊕) | Radius (R⊕) | Period (d) | Distance (AU) | Eq. temp (K) | Discovered |
|---|---|---|---|---|---|---|---|
| 55 Cnc e | Super-Earth | 7.99 | 1.88 | 0.74 | 0.0154 | 1,958 | 2004 |
| 55 Cnc b | Neptune-like | 263.98 | 13.90 | 14.65 | 0.1180 | 700 | 1996 |
| 55 Cnc c | Neptune-like | 54.47 | 8.51 | 44.39 | 0.2470 | — | 2004 |
| 55 Cnc f | Neptune-like | 44.81 | 7.59 | 260.58 | 0.8020 | — | 2007 |
| 55 Cnc d | Neptune-like | 1232.49 | 13.00 | 4799.00 | 5.6000 | — | 2002 |
The planets in detail
55 Cnc e is a Super-Earth with about 1.88 Earth radii and 7.99 Earth masses. It orbits 55 Cnc at 0.0154 AU with a 0.7-day year, soaked in over 2658× Earth's stellar flux, and an extreme equilibrium temperature exceeding 1958 K. The planet transits its host star, which is how its radius and (when combined with mass) bulk density are pinned down. It was confirmed in 2004 via radial velocity (Doppler) measurements.
55 Cnc b is a Neptune-like world with about 13.90 Earth radii and 263.98 Earth masses. It orbits 55 Cnc at 0.1180 AU with a 14.7-day year, and a scorching equilibrium temperature of 700 K. It was confirmed in 1996 via radial velocity (Doppler) measurements.
55 Cnc c is a Neptune-like world with about 8.51 Earth radii and 54.47 Earth masses. It orbits 55 Cnc at 0.2470 AU with a 44.4-day year, and no published equilibrium temperature. It was confirmed in 2004 via radial velocity (Doppler) measurements.
55 Cnc f is a Neptune-like world with about 7.59 Earth radii and 44.81 Earth masses. It orbits 55 Cnc at 0.8020 AU with a 261-day year, and no published equilibrium temperature. It was confirmed in 2007 via radial velocity (Doppler) measurements.
55 Cnc d is a Neptune-like world with about 13.00 Earth radii and 1232.49 Earth masses. It orbits 55 Cnc at 5.6000 AU with a 13.1-Earth-year orbit, and no published equilibrium temperature. It was confirmed in 2002 via radial velocity (Doppler) measurements.
Discovery
The 55 Cnc system was first identified in 1996, with confirmation work continuing through 2007 using radial velocity (Doppler) measurements. Detection facilities: McDonald Observatory, Lick Observatory, Multiple Observatories.
Observing from Earth
Exoplanets cannot be resolved visually with amateur telescopes — the host star's glare is overwhelming and even space-based direct imaging requires sophisticated coronagraphs. What you can observe is the host star itself at right ascension 133.1468°, declination 28.3298°. Because 1 planet transits from our perspective, advanced amateurs with photometric setups can sometimes detect the resulting brightness dips. Use the 3D orrery above to inspect orbital geometry, planetary scale, and the habitable-zone overlay — the orbits are computed from the published Keplerian elements and animate at user-controlled time rates.
