Key parameters at a glance

A radius of 3.46 Earth radii
A mass of 11.82 Earth masses
Surface gravity around 0.99 g
An orbital period of 271.674 days
Semi-major axis 0.8098 AU
Distance from Earth 125.40 light-years
Earth Similarity Index 0.592
Travel time at Voyager 1 speed 2,211,397 years

2 siblings around HD 31527

HD 31527 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 31527 b	Sub-Neptune	3.22	10.47	16.554	—	2019
HD 31527 c	Sub-Neptune	3.85	14.16	51.205	—	2019
HD 31527 d this	Sub-Neptune	3.46	11.82	271.674	—	2019

HD 31527 d Planet Profile

Physical Specs

Radius

3.46 R⊕

Radius (Jupiter)

0.309 R♃

Mass

11.82 M⊕

Mass (Jupiter)

0.037 M♃

Density

1.57 g/cm³

Surface Gravity

0.99 g (Earth)

Classification

Planet Type

Sub-Neptune

ESI Score 0.592

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

#193of 1978

top 9.7%

This planet

3.46R⊕

Sub-Neptune median

2.71R⊕

Nearest-size peers

HD 24085 b 3.46 R⊕ TOI-1853 b 3.46 R⊕ HD 69830 c 3.46 R⊕

Metric	Earth	HD 31527 d	Jupiter
Radius (R⊕)	1.00	3.46	11.21
Mass (M⊕)	1.00	11.82	317.83
Density (g/cm³)	5.51	1.57	1.33
Surface Gravity (g)	1.00	0.99	2.53
Insolation (S⊕)	1.00	—	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Minimum mass (M sin i)	11.820 M⊕	Lower bound from radial-velocity fitting.

Star Catalogue Identifiers

HD 31527

HIP

HIP 22905

TIC

TIC 146322354

Gaia DR2

Gaia DR2 2972622770521857664

Gaia DR3

Gaia DR3 2972622770521857664

System

HD 31527

Percentile among Sub-Neptune cohort

Radius 3.460 R⊕ · percentile 90 / cohort 1978

Mass 11.820 M⊕ · percentile 84 / cohort 1978

Orbital period 271.67 d · percentile 99 / cohort 1946

Distance 38.45 pc · percentile 9 / cohort 1975

ESI 0.592 · percentile 81 / cohort 1978

Orbit & Habitability

Orbital Dynamics

Period

271.674 days

Semi-major axis

0.8098 AU

Eccentricity

0.240

Inclination

— °

Year Length

A year here lasts approximately 271.67 Earth days (74.4% of a terrestrial year) on a mildly elliptical path at a mean orbital distance of 0.8098 AU.

Eq. Temperature

—

Insolation (S⊕)

—

Earth = 1.00

Earth Similarity (ESI)

0.592

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 45184 b · Sub-Neptune HD 51608 b · Sub-Neptune HD 136352 d · Sub-Neptune HD 20781 e · Sub-Neptune

Host System: HD 31527

Spectral Class

G-type yellow (Sun-like)

Effective Temperature

5,898 K — hotter than the Sun (5,778 K)

Estimated Age

—

Stellar Radius

1.074 R☉

Stellar Mass

0.960 M☉

Metallicity [Fe/H]

-0.17

Extended Stellar Properties

Surface gravity (log g)

4.450 dex

Stellar density

1.206 g/cm³

Systemic radial velocity

25.66 km/s

Rotational v·sin i

1.90 km/s

Rotation period

20.30 days

Metallicity ratio

[Fe/H]

Distance

38.45 parsec

Light-years 125.40 ly

V-band magnitude

7.49 mag

Voyager-speed travel 2,211,397 yr

Multi-band Host Photometry — 11 bands

Astrometric Data

Parallax

25.981 mas

Total Proper Motion

146.051 mas/yr

PM Right Ascension

-65.90 mas/yr

PM Declination

130.34 mas/yr

Galactic Cartesian (pc)

x = 0.255 · y = 0.883 · z = -0.395

Equatorial (J2000)

RA 73.90962° · Dec -23.24132°

Galactic ℓ, b

223.388° · -35.153°

Ecliptic λ, β

68.692° · -45.498°

HTM-20 index

692950005