Key parameters at a glance

A radius of 9.71 Earth radii
A mass of 68.06 Earth masses
Surface gravity around 0.72 g
An orbital period of 532.580 days
Semi-major axis 0.9120 AU
Distance from Earth 35.92 light-years
Earth Similarity Index 0.312
Travel time at Voyager 1 speed 633,516 years

1 sibling around GJ 1148

GJ 1148 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
GJ 1148 b	Gas Giant	11.90	96.70	41.380	—	2010
GJ 1148 c this	Neptune-like	9.71	68.06	532.580	—	2017

GJ 1148 c Planet Profile

Physical Specs

Radius

9.71 R⊕

Radius (Jupiter)

0.866 R♃

Mass

68.06 M⊕

Mass (Jupiter)

0.214 M♃

Density

0.41 g/cm³

Surface Gravity

0.72 g (Earth)

Classification

Planet Type

Neptune-like

ESI Score 0.312

HZ Position Unknown

Controversial No

Discovery

Year 2017

Method Radial Velocity

Facility Calar Alto Observatory

Telescope 3.5 m telescope

Size rank in cohort

Rank by radius

#24of 574

top 4.0%

This planet

9.71R⊕

Neptune-like median

6.39R⊕

Nearest-size peers

HAT-P-20 b 9.72 R⊕ Kepler-51 d 9.70 R⊕ Kepler-714 b 9.67 R⊕

Metric	Earth	GJ 1148 c	Jupiter
Radius (R⊕)	1.00	9.71	11.21
Mass (M⊕)	1.00	68.06	317.83
Density (g/cm³)	5.51	0.41	1.33
Surface Gravity (g)	1.00	0.72	2.53
Insolation (S⊕)	1.00	—	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Minimum mass (M sin i)	68.060 M⊕	Lower bound from radial-velocity fitting.

Star Catalogue Identifiers

HIP

HIP 57050

TIC

TIC 115869504

Gaia DR2

Gaia DR2 772430527947893632

Gaia DR3

Gaia DR3 772430527947893632

System

GJ 1148

Percentile among Neptune-like cohort

Radius 9.710 R⊕ · percentile 96 / cohort 574

Mass 68.060 M⊕ · percentile 85 / cohort 574

Orbital period 532.58 d · percentile 96 / cohort 524

Distance 11.01 pc · percentile 3 / cohort 572

ESI 0.312 · percentile 52 / cohort 574

Orbit & Habitability

Orbital Dynamics

Period

532.580 days

Semi-major axis

0.9120 AU

Eccentricity

0.342

Inclination

— °

Year Length

A year here lasts about 1.46 Earth years on a highly eccentric trajectory at a mean orbital distance of 0.9120 AU.

Extended Orbital Architecture

RV semi-amplitude (K)

11.340 m/s

Transit mid-time (BJD)

2,454,769.0000

Long. of periastron (ω)

210.40°

Angular separation (arcsec)

82.80000

Eq. Temperature

—

Insolation (S⊕)

—

Earth = 1.00

Earth Similarity (ESI)

0.312

0 = alien, 1 = Earth-identical

Discovery Paper

Primary reference

Trifonov et al. 2018

Instrument

CARMENES

Publication

2018-02

Observation locale

Ground

Host System: GJ 1148

Spectral Class

M-type red dwarf

Effective Temperature

3,287 K — cooler than the Sun (5,778 K)

Estimated Age

—

Stellar Radius

0.359 R☉

Stellar Mass

0.344 M☉

Metallicity [Fe/H]

0.16

Extended Stellar Properties

Surface gravity (log g)

4.866 dex

Stellar density

10.526 g/cm³

Systemic radial velocity

-9.10 km/s

Metallicity ratio

[Fe/H]

Distance

11.01 parsec

Light-years 35.92 ly

V-band magnitude

11.94 mag

Voyager-speed travel 633,516 yr

Multi-band Host Photometry — 17 bands

Astrometric Data

Parallax

90.762 mas

Total Proper Motion

582.643 mas/yr

PM Right Ascension

-575.65 mas/yr

PM Declination

-89.97 mas/yr

Galactic Cartesian (pc)

x = -0.732 · y = 0.058 · z = 0.679

Equatorial (J2000)

RA 175.43261° · Dec 42.75159°

Galactic ℓ, b

160.618° · 68.916°

Ecliptic λ, β

156.142° · 36.837°

HTM-20 index

-1865794278

Observation Record

Photometric series

RV measurements

Stellar spectra