Key parameters at a glance

A radius of 2.04 Earth radii
A mass of 4.80 Earth masses
Surface gravity around 1.15 g
An orbital period of 89.680 days
Semi-major axis 0.3625 AU
Equilibrium temperature 388 K (115 °C)
Distance from Earth 19.58 light-years
Earth Similarity Index 0.663
Travel time at Voyager 1 speed 345,266 years

Context from the literature

82 G. Eridani d is an exoplanet, possibly rocky, orbiting the solar-type star 82 G. Eridani. It is at least five times more massive than Earth and has an orbit partially within the habitable zone of its host star. Depending on its physical characteristics, which are poorly known, it could harbour life.

Excerpted from Wikipedia · full article

2 siblings around HD 20794

HD 20794 d shares its host star with 2 other confirmed planets. Side-by-side measurements below.

Planet	Type	Radius (R⊕)	Mass (M⊕)	Period (d)	Eq. T (K)	Year
HD 20794 b	Super-Earth	1.45	2.70	18.314	660	2011
HD 20794 d this	Sub-Neptune	2.04	4.80	89.680	388	2011
HD 20794 f	Sub-Neptune	2.28	5.82	647.600	—	2025

HD 20794 d Planet Profile

Physical Specs

Radius

2.04 R⊕

Radius (Jupiter)

0.182 R♃

Mass

4.80 M⊕

Mass (Jupiter)

0.015 M♃

Density

3.11 g/cm³

Surface Gravity

1.15 g (Earth)

Classification

Planet Type

Sub-Neptune

ESI Score 0.663

HZ Position Unknown

Controversial No

Discovery

Year 2011

Method Radial Velocity

Facility La Silla Observatory

Telescope 3.6 m ESO Telescope

Size rank in cohort

Rank by radius

#1904of 1978

top 96.2%

This planet

2.04R⊕

Sub-Neptune median

2.71R⊕

Nearest-size peers

TOI-2081 b 2.04 R⊕ Kepler-230 c 2.04 R⊕ Kepler-48 d 2.04 R⊕

Metric	Earth	HD 20794 d	Jupiter
Radius (R⊕)	1.00	2.04	11.21
Mass (M⊕)	1.00	4.80	317.83
Density (g/cm³)	5.51	3.11	1.33
Surface Gravity (g)	1.00	1.15	2.53
Insolation (S⊕)	1.00	—	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Minimum mass (M sin i)	2.980 M⊕	Lower bound from radial-velocity fitting.
Computed mass	4.800 M⊕	Model-computed mass (e.g. from mass-radius relation).

Star Catalogue Identifiers

HD 20794

HIP

HIP 15510

TIC

TIC 301051051

Gaia DR2

Gaia DR2 4847957293277762560

Gaia DR3

Gaia DR3 4847957293278177024

System

HD 20794

Percentile among Sub-Neptune cohort

Radius 2.040 R⊕ · percentile 3 / cohort 1978

Mass 4.800 M⊕ · percentile 5 / cohort 1978

Orbital period 89.68 d · percentile 93 / cohort 1946

Distance 6.00 pc · percentile 0 / cohort 1975

ESI 0.663 · percentile 89 / cohort 1978

Orbit & Habitability

Orbital Dynamics

Period

89.680 days

Semi-major axis

0.3625 AU

Eccentricity

0.077

Inclination

90.00 °

Year Length

A year here lasts approximately 89.68 Earth days (24.6% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.3625 AU.

Extended Orbital Architecture

RV semi-amplitude (K)

0.502 m/s

Transit mid-time (BJD)

2,460,356.2000

Long. of periastron (ω)

54.00°

Angular separation (arcsec)

60.40000

Eq. Temperature

388K

(115 °C)

Insolation (S⊕)

—

Earth = 1.00

Earth Similarity (ESI)

0.663

0 = alien, 1 = Earth-identical

Insufficient insolation data — the surface is too hot to retain surface water.

Discovery Paper

Primary reference

Pepe et al. 2011

Instrument

HARPS Spectrograph

Publication

2011-10

Observation locale

Ground

Discovery cohort

Planets confirmed in 2011 at La Silla Observatory (10 shown).

GJ 433 b · Sub-Neptune HD 192310 b · Neptune-like HD 20794 b · Super-Earth HD 7449 b · Gas Giant HD 192310 c · Neptune-like HD 217786 b · Gas Giant HIP 5158 c · Gas Giant HD 137388 b · Neptune-like HD 204941 b · Gas Giant HD 7199 b · Unclassified

Host System: HD 20794

Spectral Class

G-type yellow (Sun-like)

Effective Temperature

5,368 K — cooler than the Sun (5,778 K)

Estimated Age

5.76 Gyr — older than the Sun (4.6 Gyr)

Stellar Radius

0.930 R☉

Stellar Mass

0.790 M☉

Metallicity [Fe/H]

-0.42

Extended Stellar Properties

Surface gravity (log g)

4.390 dex

Stellar density

1.704 g/cm³

Systemic radial velocity

87.88 km/s

Rotational v·sin i

3.00 km/s

Activity index (log R'HK)

-4.980

Metallicity ratio

[Fe/H]

Distance

6.00 parsec

Light-years 19.58 ly

V-band magnitude

4.26 mag

Voyager-speed travel 345,266 yr

Multi-band Host Photometry — 8 bands

Astrometric Data

Parallax

166.561 mas

Total Proper Motion

3,120.505 mas/yr

PM Right Ascension

3,033.73 mas/yr

PM Declination

730.78 mas/yr

Galactic Cartesian (pc)

x = 0.470 · y = 0.560 · z = -0.683

Equatorial (J2000)

RA 49.99977° · Dec -43.06665°

Galactic ℓ, b

250.734° · -56.065°

Ecliptic λ, β

27.244° · -58.115°

HTM-20 index

-869587511

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