Key parameters at a glance
- A radius of 13.90 Earth radii
- A mass of 263.98 Earth masses
- Surface gravity around 1.37 g
- An orbital period of 14.652 days
- Semi-major axis 0.1180 AU
- Equilibrium temperature 700 K (427 °C)
- Distance from Earth 41.05 light-years
- Earth Similarity Index 0.188
- Travel time at Voyager 1 speed 723,888 years
4 siblings around 55 Cnc
55 Cnc b shares its host star with 4 other confirmed planets. Side-by-side measurements below.
| Planet | Type | Radius (R⊕) | Mass (M⊕) | Period (d) | Eq. T (K) | Year |
|---|---|---|---|---|---|---|
| 55 Cnc e | Super-Earth | 1.88 | 7.99 | 0.737 | 1,958 | 2004 |
| 55 Cnc b this | Gas Giant | 13.90 | 263.98 | 14.652 | 700 | 1996 |
| 55 Cnc c | Neptune-like | 8.51 | 54.47 | 44.394 | — | 2004 |
| 55 Cnc f | Neptune-like | 7.59 | 44.81 | 260.580 | — | 2007 |
| 55 Cnc d | Gas Giant | 13.00 | 1,232.49 | 4,799.000 | — | 2002 |
55 Cnc b Planet Profile
Physical Specs
Classification
Planet Type
Gas Giant
Discovery
Size rank in cohort
Rank by radius
#456of 1771
top 25.7%
This planet
13.90R⊕
Gas Giant median
13.52R⊕
Nearest-size peers
| Metric | Earth | 55 Cnc b | Jupiter |
|---|---|---|---|
| Radius (R⊕) | 1.00 | 13.90 | 11.21 |
| Mass (M⊕) | 1.00 | 263.98 | 317.83 |
| Density (g/cm³) | 5.51 | 0.54 | 1.33 |
| Surface Gravity (g) | 1.00 | 1.37 | 2.53 |
| Insolation (S⊕) | 1.00 | — | 0.037 |
Alternative Mass Estimates
| Method | Value | Interpretation |
|---|---|---|
| Best measured mass | 263.979 M⊕ | Direct mass measurement (not derived). |
| Minimum mass (M sin i) | 276.000 M⊕ | Lower bound from radial-velocity fitting. |
Star Catalogue Identifiers
HD
HD 75732
HIP
HIP 43587
TIC
TIC 332064670
Gaia DR2
Gaia DR2 704967037090946688
Gaia DR3
Gaia DR3 704967037090946688
System
55 Cnc
Percentile among Gas Giant cohort
Orbit & Habitability
Orbital Dynamics
Year Length
A year here lasts approximately 14.65 Earth days (4.0% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.1180 AU.
Extended Orbital Architecture
RV semi-amplitude (K)
71.500 m/s
Transit mid-time (BJD)
2,455,495.5950
Long. of periastron (ω)
23.00°
Angular separation (arcsec)
9.38000
Eq. Temperature
700K
(427 °C)
Insolation (S⊕)
—
Earth = 1.00
Earth Similarity (ESI)
0.188
0 = alien, 1 = Earth-identical
Insufficient insolation data — the surface is too hot to retain surface water.
Discovery Paper
Primary reference
Butler et al. 1997Instrument
Hamilton Echelle Spectrograph
Publication
1997-01
Observation locale
Ground
Discovery cohort
Planets confirmed in 1996 at Lick Observatory (4 shown).
Host System: 55 Cnc
Spectral Class
G-type yellow (Sun-like)
Effective Temperature
5,198 K — cooler than the Sun (5,778 K)
Estimated Age
10.00 Gyr — older than the Sun (4.6 Gyr)
Stellar Radius
0.980 R☉
Stellar Mass
1.015 M☉
Metallicity [Fe/H]
0.39
Extended Stellar Properties
Surface gravity (log g)
4.300 dex
Stellar density
1.521 g/cm³
Systemic radial velocity
27.41 km/s
Rotational v·sin i
1.06 km/s
Rotation period
39.00 days
Activity index (log R'HK)
-5.040
Metallicity ratio
[M/H]
Multi-band Host Photometry — 11 bands
Astrometric Data
Parallax
79.427 mas
Total Proper Motion
539.133 mas/yr
PM Right Ascension
-485.87 mas/yr
PM Declination
-233.65 mas/yr
Galactic Cartesian (pc)
x = -0.602 · y = 0.642 · z = 0.475
Equatorial (J2000)
RA 133.14684° · Dec 28.32982°
Galactic ℓ, b
196.795° · 37.697°
Ecliptic λ, β
127.727° · 10.366°
HTM-20 index
570333148
Observation Record
Photometric series
1
RV measurements
9
Stellar spectra
11
Archive notes
4
Similar Worlds
HD 167768 b
Gas Giant · G-type yellow (Sun-like)
Radius 13.90 R⊕ · 349.7 ly
HD 155358 c
Gas Giant · G-type yellow (Sun-like)
Radius 13.90 R⊕ · 142.3 ly
HD 134987 c
Gas Giant · G-type yellow (Sun-like)
Radius 13.90 R⊕ · 85.4 ly
HD 148156 b
Gas Giant · G-type yellow (Sun-like)
Radius 13.90 R⊕ · 186.3 ly
HD 163607 b
Gas Giant · G-type yellow (Sun-like)
Radius 13.90 R⊕ · 221.1 ly
HD 136925 b
Gas Giant · G-type yellow (Sun-like)
Radius 13.90 R⊕ · 156.1 ly