Key parameters at a glance

A radius of 2.51 Earth radii
A mass of 6.83 Earth masses
Surface gravity around 1.08 g
An orbital period of 1.938 days
Semi-major axis 0.0208 AU
Distance from Earth 15.25 light-years
Earth Similarity Index 0.702
Travel time at Voyager 1 speed 268,905 years
Almost certainly tidally locked to its host star given the close orbit

Context from the literature

Gliese 876 d is an exoplanet 15.2 light-years away in the constellation of Aquarius. The planet was the third planet discovered orbiting the red dwarf Gliese 876, and is the innermost planet in the system. It was the lowest-mass known exoplanet apart from the pulsar planets orbiting PSR B1257+12 at the time of its discovery. Due to its mass, it can be categorized as a super-Earth.

Excerpted from Wikipedia · full article

3 siblings around GJ 876

GJ 876 d shares its host star with 3 other confirmed planets. Side-by-side measurements below.

Planet	Type	Radius (R⊕)	Mass (M⊕)	Period (d)	Eq. T (K)	Year
GJ 876 d this	Sub-Neptune	2.51	6.83	1.938	—	2005
GJ 876 c	Gas Giant	14.00	226.98	30.088	—	2000
GJ 876 b	Gas Giant	13.30	723.22	61.117	—	1998
GJ 876 e	Sub-Neptune	3.92	14.60	124.260	—	2010

GJ 876 d Planet Profile

Physical Specs

Radius

2.51 R⊕

Radius (Jupiter)

0.224 R♃

Mass

6.83 M⊕

Mass (Jupiter)

0.021 M♃

Density

2.37 g/cm³

Surface Gravity

1.08 g (Earth)

Classification

Planet Type

Sub-Neptune

ESI Score 0.702

HZ Position Unknown

Controversial No

Discovery

Year 2005

Method Radial Velocity

Facility W. M. Keck Observatory

Telescope 10 m Keck I Telescope

Size rank in cohort

Rank by radius

#1159of 1978

top 58.5%

This planet

2.51R⊕

Sub-Neptune median

2.71R⊕

Nearest-size peers

Kepler-445 c 2.51 R⊕ Kepler-309 c 2.51 R⊕ Kepler-239 c 2.51 R⊕

Metric	Earth	GJ 876 d	Jupiter
Radius (R⊕)	1.00	2.51	11.21
Mass (M⊕)	1.00	6.83	317.83
Density (g/cm³)	5.51	2.37	1.33
Surface Gravity (g)	1.00	1.08	2.53
Insolation (S⊕)	1.00	—	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	6.830 M⊕	Direct mass measurement (not derived).
Minimum mass (M sin i)	6.910 M⊕	Lower bound from radial-velocity fitting.
Computed mass	8.061 M⊕	Model-computed mass (e.g. from mass-radius relation).

Star Catalogue Identifiers

HIP

HIP 113020

TIC

TIC 188580272

Gaia DR2

Gaia DR2 2603090003484152064

Gaia DR3

Gaia DR3 2603090003484152064

System

GJ 876

Percentile among Sub-Neptune cohort

Radius 2.510 R⊕ · percentile 41 / cohort 1978

Mass 6.830 M⊕ · percentile 38 / cohort 1978

Orbital period 1.94 d · percentile 2 / cohort 1946

Distance 4.68 pc · percentile 0 / cohort 1975

ESI 0.702 · percentile 92 / cohort 1978

Orbit & Habitability

Orbital Dynamics

Period

1.938 days

Semi-major axis

0.0208 AU

Eccentricity

0.207

Inclination

59.00 °

Year Length

A year here lasts approximately 1.94 Earth days (0.5% of a terrestrial year) on a mildly elliptical path at a mean orbital distance of 0.0208 AU.

Extended Orbital Architecture

RV semi-amplitude (K)

6.560 m/s

Transit mid-time (BJD)

2,455,200.0640

Long. of periastron (ω)

234.00°

Angular separation (arcsec)

4.45000

Eq. Temperature

—

Insolation (S⊕)

—

Earth = 1.00

Earth Similarity (ESI)

0.702

0 = alien, 1 = Earth-identical

Insufficient insolation data. Close-orbiting tidally-locked around a cool host.

Discovery Paper

Primary reference

Rivera et al. 2005

Instrument

HIRES Spectrometer

Publication

2005-11

Observation locale

Ground

Discovery cohort

Planets confirmed in 2005 at W. M. Keck Observatory (12 shown).

HD 190360 c · Neptune-like HIP 14810 b · Gas Giant HD 128311 c · Gas Giant HD 66428 b · Gas Giant HD 50499 b · Gas Giant HD 107148 b · Neptune-like HD 108874 c · Gas Giant HD 109749 b · Gas Giant HD 37124 d · Gas Giant HD 11964 b · Gas Giant HD 99109 b · Gas Giant HD 164922 b · Gas Giant

Host System: GJ 876

Spectral Class

M-type red dwarf

Effective Temperature

3,294 K — cooler than the Sun (5,778 K)

Estimated Age

1.00 Gyr — younger than the Sun (4.6 Gyr)

Stellar Radius

0.300 R☉

Stellar Mass

0.320 M☉

Metallicity [Fe/H]

0.21

Extended Stellar Properties

Surface gravity (log g)

4.872 dex

Stellar density

10.866 g/cm³

Systemic radial velocity

-1.60 km/s

Rotational v·sin i

0.16 km/s

Metallicity ratio

[Fe/H]

Distance

4.68 parsec

Light-years 15.25 ly

V-band magnitude

10.16 mag

Voyager-speed travel 268,905 yr

Multi-band Host Photometry — 13 bands

Astrometric Data

Parallax

213.867 mas

Total Proper Motion

1,171.101 mas/yr

PM Right Ascension

957.96 mas/yr

PM Declination

-673.64 mas/yr

Galactic Cartesian (pc)

x = 0.928 · y = -0.278 · z = -0.246

Equatorial (J2000)

RA 343.32397° · Dec -14.26660°

Galactic ℓ, b

52.003° · -59.635°

Ecliptic λ, β

339.168° · -6.631°

HTM-20 index

-1428809485

Observation Record

Photometric series

RV measurements

Stellar spectra

Archive notes

Wikipedia → Image: Wikimedia Commons · Trent Schindler, National Science Foundation · Public domain