Key parameters at a glance

A radius of 4.34 Earth radii
A mass of 17.37 Earth masses
Surface gravity around 0.92 g
An orbital period of 53.736 days
Semi-major axis 0.2586 AU
Distance from Earth 108.46 light-years
Earth Similarity Index 0.519
Travel time at Voyager 1 speed 1,912,748 years

1 sibling around HD 21693

HD 21693 c shares its host star with 1 other confirmed planet. Side-by-side measurements below.

Planet	Type	Radius (R⊕)	Mass (M⊕)	Period (d)	Eq. T (K)	Year
HD 21693 b	Sub-Neptune	2.80	8.23	22.679	—	2019
HD 21693 c this	Neptune-like	4.34	17.37	53.736	—	2019

HD 21693 c Planet Profile

Physical Specs

Radius

4.34 R⊕

Radius (Jupiter)

0.387 R♃

Mass

17.37 M⊕

Mass (Jupiter)

0.055 M♃

Density

1.17 g/cm³

Surface Gravity

0.92 g (Earth)

Classification

Planet Type

Neptune-like

ESI Score 0.519

HZ Position Unknown

Controversial No

Discovery

Year 2019

Method Radial Velocity

Facility La Silla Observatory

Telescope 3.6 m ESO Telescope

Size rank in cohort

Rank by radius

#484of 574

top 84.1%

This planet

4.34R⊕

Neptune-like median

6.39R⊕

Nearest-size peers

TOI-470 b 4.34 R⊕ K2-245 b 4.34 R⊕ Kepler-413 b 4.35 R⊕

Metric	Earth	HD 21693 c	Jupiter
Radius (R⊕)	1.00	4.34	11.21
Mass (M⊕)	1.00	17.37	317.83
Density (g/cm³)	5.51	1.17	1.33
Surface Gravity (g)	1.00	0.92	2.53
Insolation (S⊕)	1.00	—	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Minimum mass (M sin i)	17.370 M⊕	Lower bound from radial-velocity fitting.

Star Catalogue Identifiers

HD 21693

HIP

HIP 16085

TIC

TIC 197792776

Gaia DR2

Gaia DR2 4729947569262040960

Gaia DR3

Gaia DR3 4729947569262040960

System

HD 21693

Percentile among Neptune-like cohort

Radius 4.340 R⊕ · percentile 15 / cohort 574

Mass 17.370 M⊕ · percentile 19 / cohort 574

Orbital period 53.74 d · percentile 72 / cohort 524

Distance 33.26 pc · percentile 10 / cohort 572

ESI 0.519 · percentile 94 / cohort 574

Orbit & Habitability

Orbital Dynamics

Period

53.736 days

Semi-major axis

0.2586 AU

Eccentricity

0.070

Inclination

— °

Year Length

A year here lasts approximately 53.74 Earth days (14.7% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.2586 AU.

Eq. Temperature

—

Insolation (S⊕)

—

Earth = 1.00

Earth Similarity (ESI)

0.519

0 = alien, 1 = Earth-identical

Discovery Paper

Primary reference

Udry et al. 2019

Instrument

HARPS Spectrograph

Publication

2019-02

Observation locale

Ground

Discovery cohort

Planets confirmed in 2019 at La Silla Observatory (12 shown).

HD 20781 b · Rocky Terrestrial HD 20781 c · Sub-Neptune HD 21693 b · Sub-Neptune HD 45184 c · Sub-Neptune HD 134060 b · Sub-Neptune HD 31527 b · Sub-Neptune HD 20781 d · Sub-Neptune HD 20003 b · Sub-Neptune HD 31527 d · Sub-Neptune HD 45184 b · Sub-Neptune HD 51608 b · Sub-Neptune HD 136352 d · Sub-Neptune

Host System: HD 21693

Spectral Class

G-type yellow (Sun-like)

Effective Temperature

5,430 K — cooler than the Sun (5,778 K)

Estimated Age

—

Stellar Radius

0.914 R☉

Stellar Mass

0.800 M☉

Metallicity [Fe/H]

0.00

Extended Stellar Properties

Surface gravity (log g)

4.370 dex

Stellar density

1.703 g/cm³

Systemic radial velocity

39.10 km/s

Rotational v·sin i

1.60 km/s

Rotation period

35.20 days

Metallicity ratio

[Fe/H]

Distance

33.26 parsec

Light-years 108.46 ly

V-band magnitude

7.95 mag

Voyager-speed travel 1,912,748 yr

Multi-band Host Photometry — 11 bands

Astrometric Data

Parallax

30.042 mas

Total Proper Motion

266.058 mas/yr

PM Right Ascension

248.65 mas/yr

PM Declination

94.65 mas/yr

Galactic Cartesian (pc)

x = 0.325 · y = 0.413 · z = -0.851

Equatorial (J2000)

RA 51.80405° · Dec -58.32327°

Galactic ℓ, b

272.908° · -48.724°

Ecliptic λ, β

7.040° · -70.902°

HTM-20 index

1230760665