Key parameters at a glance

A radius of 13.10 Earth radii
A mass of 1,051.06 Earth masses
Surface gravity around 6.12 g
An orbital period of 1,005.570 days
Semi-major axis 2.1040 AU
Distance from Earth 330.27 light-years
Earth Similarity Index 0.404
Travel time at Voyager 1 speed 5,824,233 years

81 Cet b Planet Profile

Physical Specs

Radius

13.10 R⊕

Radius (Jupiter)

1.170 R♃

Mass

1,051.06 M⊕

Mass (Jupiter)

3.307 M♃

Density

2.57 g/cm³

Surface Gravity

6.12 g (Earth)

Classification

Planet Type

Gas Giant

ESI Score 0.404

HZ Position Unknown

Controversial No

Discovery

Year 2008

Method Radial Velocity

Facility Okayama Astrophysical Observatory

Telescope 1.88 m Telescope

Size rank in cohort

Rank by radius

#910of 1771

top 51.3%

This planet

13.10R⊕

Gas Giant median

13.52R⊕

Nearest-size peers

GJ 3021 b 13.10 R⊕ HD 221287 b 13.10 R⊕ HD 37605 c 13.10 R⊕

Metric	Earth	81 Cet b	Jupiter
Radius (R⊕)	1.00	13.10	11.21
Mass (M⊕)	1.00	1,051.06	317.83
Density (g/cm³)	5.51	2.57	1.33
Surface Gravity (g)	1.00	6.12	2.53
Insolation (S⊕)	1.00	—	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Minimum mass (M sin i)	1,051.059 M⊕	Lower bound from radial-velocity fitting.

Star Catalogue Identifiers

HD 16400

HIP

HIP 12247

TIC

TIC 35725282

Gaia DR2

Gaia DR2 2495420602212048640

Gaia DR3

Gaia DR3 2495420602212048640

System

81 Cet

Percentile among Gas Giant cohort

Radius 13.100 R⊕ · percentile 46 / cohort 1771

Mass 1,051.059 M⊕ · percentile 68 / cohort 1747

Orbital period 1,005.57 d · percentile 77 / cohort 1533

Distance 101.26 pc · percentile 35 / cohort 1759

ESI 0.404 · percentile 87 / cohort 1771

Orbit & Habitability

Orbital Dynamics

Period

1,005.570 days

Semi-major axis

2.1040 AU

Eccentricity

0.037

Inclination

— °

Year Length

A year here lasts about 2.75 Earth years on a nearly circular orbit at a mean orbital distance of 2.1040 AU.

Eq. Temperature

—

Insolation (S⊕)

—

Earth = 1.00

Earth Similarity (ESI)

0.404

0 = alien, 1 = Earth-identical

Discovery Paper

Primary reference

Sato et al. 2008

Instrument

HIDES Echelle Spectrograph

Publication

2008-12

Observation locale

Ground

Discovery cohort

Planets confirmed in 2008 at Okayama Astrophysical Observatory (3 shown).

14 And b · Gas Giant 18 Del b · Gas Giant 6 Lyn b · Gas Giant

Host System: 81 Cet

Spectral Class

G-type yellow (Sun-like)

Effective Temperature

4,734 K — cooler than the Sun (5,778 K)

Estimated Age

—

Stellar Radius

11.210 R☉

Stellar Mass

1.230 M☉

Metallicity [Fe/H]

-0.11

Extended Stellar Properties

Surface gravity (log g)

2.410 dex

Systemic radial velocity

9.25 km/s

Rotational v·sin i

1.80 km/s

Metallicity ratio

[Fe/H]

Distance

101.26 parsec

Light-years 330.27 ly

V-band magnitude

5.64 mag

Voyager-speed travel 5,824,233 yr

Multi-band Host Photometry — 11 bands

Astrometric Data

Parallax

9.849 mas

Total Proper Motion

60.391 mas/yr

PM Right Ascension

42.07 mas/yr

PM Declination

-43.33 mas/yr

Galactic Cartesian (pc)

x = 0.771 · y = 0.634 · z = -0.059

Equatorial (J2000)

RA 39.42436° · Dec -3.39636°

Galactic ℓ, b

174.487° · -55.250°

Ecliptic λ, β

35.890° · -17.850°

HTM-20 index

-1022546720