Key parameters at a glance

A radius of 12.50 Earth radii
A mass of 2,796.89 Earth masses
Surface gravity around 17.90 g
An orbital period of 1,515.000 days
Semi-major axis 2.5180 AU
Distance from Earth 146.15 light-years
Earth Similarity Index 0.400
Travel time at Voyager 1 speed 2,577,439 years

HD 171238 b Planet Profile

Physical Specs

Radius

12.50 R⊕

Radius (Jupiter)

1.120 R♃

Mass

2,796.89 M⊕

Mass (Jupiter)

8.800 M♃

Density

7.87 g/cm³

Surface Gravity

17.90 g (Earth)

Classification

Planet Type

Gas Giant

ESI Score 0.400

HZ Position Unknown

Controversial No

Discovery

Year 2009

Method Radial Velocity

Facility La Silla Observatory

Telescope 1.2 m Leonhard Euler Telescope

Size rank in cohort

Rank by radius

#1235of 1771

top 69.7%

This planet

12.50R⊕

Gas Giant median

13.52R⊕

Nearest-size peers

HD 156279 c 12.50 R⊕ HD 33283 b 12.50 R⊕ HD 156279 b 12.50 R⊕

Metric	Earth	HD 171238 b	Jupiter
Radius (R⊕)	1.00	12.50	11.21
Mass (M⊕)	1.00	2,796.89	317.83
Density (g/cm³)	5.51	7.87	1.33
Surface Gravity (g)	1.00	17.90	2.53
Insolation (S⊕)	1.00	—	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	2,796.890 M⊕	Direct mass measurement (not derived).
Minimum mass (M sin i)	826.036 M⊕	Lower bound from radial-velocity fitting.

Star Catalogue Identifiers

HD 171238

HIP

HIP 91085

TIC

TIC 228217280

Gaia DR2

Gaia DR2 4048636941542753152

Gaia DR3

Gaia DR3 4048636941542753152

System

HD 171238

Percentile among Gas Giant cohort

Radius 12.500 R⊕ · percentile 28 / cohort 1771

Mass 2,796.890 M⊕ · percentile 85 / cohort 1747

Orbital period 1,515.00 d · percentile 82 / cohort 1533

Distance 44.81 pc · percentile 16 / cohort 1759

ESI 0.400 · percentile 86 / cohort 1771

Orbit & Habitability

Orbital Dynamics

Period

1,515.000 days

Semi-major axis

2.5180 AU

Eccentricity

0.358

Inclination

19.10 °

Year Length

A year here lasts about 4.15 Earth years on a highly eccentric trajectory at a mean orbital distance of 2.5180 AU.

Eq. Temperature

—

Insolation (S⊕)

—

Earth = 1.00

Earth Similarity (ESI)

0.400

0 = alien, 1 = Earth-identical

Detection Signatures

Radial velocity

Stellar wobble has been measured spectroscopically.

Astrometry

Positional wobble of the host star was measured.

Discovery Paper

Primary reference

Segransan et al. 2010

Instrument

CORALIE Spectrograph

Publication

2010-02

Observation locale

Ground

Discovery cohort

Planets confirmed in 2009 at La Silla Observatory (12 shown).

GJ 581 e · Super-Earth HD 125612 c · Neptune-like HD 90156 b · Neptune-like HD 147018 c · Gas Giant HD 103197 b · Neptune-like HD 125612 d · Gas Giant HIP 70849 b · Gas Giant HD 85390 b · Neptune-like HD 190984 b · Gas Giant HD 290327 b · Gas Giant HD 147018 b · Gas Giant HD 110014 b · Gas Giant

Host System: HD 171238

Spectral Class

G-type yellow (Sun-like)

Effective Temperature

5,467 K — cooler than the Sun (5,778 K)

Estimated Age

7.00 Gyr — older than the Sun (4.6 Gyr)

Stellar Radius

1.010 R☉

Stellar Mass

0.920 M☉

Metallicity [Fe/H]

0.20

Extended Stellar Properties

Surface gravity (log g)

4.430 dex

Stellar density

1.731 g/cm³

Systemic radial velocity

21.64 km/s

Rotational v·sin i

1.48 km/s

Activity index (log R'HK)

-4.960

Metallicity ratio

[Fe/H]

Distance

44.81 parsec

Light-years 146.15 ly

V-band magnitude

8.61 mag

Voyager-speed travel 2,577,439 yr

Multi-band Host Photometry — 11 bands

Astrometric Data

Parallax

22.287 mas

Total Proper Motion

113.048 mas/yr

PM Right Ascension

-29.58 mas/yr

PM Declination

-109.11 mas/yr

Galactic Cartesian (pc)

x = 0.133 · y = -0.872 · z = -0.471

Equatorial (J2000)

RA 278.68184° · Dec -28.07278°

Galactic ℓ, b

5.945° · -9.055°

Ecliptic λ, β

277.678° · -4.865°

HTM-20 index

2005170922

Observation Record

Photometric series

Stellar spectra

Archive notes