Key parameters at a glance

A radius of 1.06 Earth radii
A mass of 1.18 Earth masses
Surface gravity around 1.05 g
An orbital period of 4.723 days
Semi-major axis 0.0365 AU
Distance from Earth 19.31 light-years
Earth Similarity Index 0.986
Travel time at Voyager 1 speed 340,593 years
Almost certainly tidally locked to its host star given the close orbit

1 sibling around GJ 273

GJ 273 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 273 c this	Rocky Terrestrial	1.06	1.18	4.723	—	2017
GJ 273 b	Super-Earth	1.51	2.89	18.650	—	2017

GJ 273 c Planet Profile

Physical Specs

Radius

1.06 R⊕

Radius (Jupiter)

0.094 R♃

Mass

1.18 M⊕

Mass (Jupiter)

0.004 M♃

Density

5.44 g/cm³

Surface Gravity

1.05 g (Earth)

Classification

Planet Type

Rocky Terrestrial

ESI Score 0.986

HZ Position Inner

Controversial No

Discovery

Year 2017

Method Radial Velocity

Facility La Silla Observatory

Telescope 3.6 m ESO Telescope

Size rank in cohort

Rank by radius

#270of 570

top 47.2%

This planet

1.06R⊕

Rocky Terrestrial median

1.01R⊕

Nearest-size peers

Kepler-1200 b 1.06 R⊕ Kepler-316 b 1.06 R⊕ Kepler-1203 b 1.06 R⊕

Metric	Earth	GJ 273 c	Jupiter
Radius (R⊕)	1.00	1.06	11.21
Mass (M⊕)	1.00	1.18	317.83
Density (g/cm³)	5.51	5.44	1.33
Surface Gravity (g)	1.00	1.05	2.53
Insolation (S⊕)	1.00	6.66	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Minimum mass (M sin i)	1.180 M⊕	Lower bound from radial-velocity fitting.

Star Catalogue Identifiers

HIP

HIP 36208

TIC

TIC 318686860

System

GJ 273

Percentile among Rocky Terrestrial cohort

Radius 1.060 R⊕ · percentile 51 / cohort 570

Mass 1.180 M⊕ · percentile 46 / cohort 570

Orbital period 4.72 d · percentile 51 / cohort 567

Distance 5.92 pc · percentile 4 / cohort 566

ESI 0.986 · percentile 98 / cohort 570

Orbit & Habitability

Orbital Dynamics

Period

4.723 days

Semi-major axis

0.0365 AU

Eccentricity

0.170

Inclination

— °

Year Length

A year here lasts approximately 4.72 Earth days (1.3% of a terrestrial year) on a mildly elliptical path at a mean orbital distance of 0.0365 AU.

Eq. Temperature

—

Insolation (S⊕)

6.66

Earth = 1.00

Earth Similarity (ESI)

0.986

0 = alien, 1 = Earth-identical

Inside the inner HZ boundary (too hot for liquid water). Close-orbiting tidally-locked around a cool host.

Discovery Paper

Primary reference

Astudillo Defru et al. 2017

Instrument

HARPS Spectrograph

Publication

2017-06

Observation locale

Ground

Discovery cohort

Planets confirmed in 2017 at La Silla Observatory (12 shown).

Ross 128 b · Rocky Terrestrial GJ 3138 b · Rocky Terrestrial GJ 3323 c · Super-Earth GJ 3323 b · Rocky Terrestrial GJ 273 b · Super-Earth GJ 3293 e · Super-Earth YZ Cet d · Rocky Terrestrial GJ 3138 c · Super-Earth YZ Cet c · Rocky Terrestrial GJ 3293 d · Sub-Neptune YZ Cet b · Rocky Terrestrial GJ 3138 d · Sub-Neptune

Host System: GJ 273

Spectral Class

M-type red dwarf

Effective Temperature

3,382 K — cooler than the Sun (5,778 K)

Estimated Age

—

Stellar Radius

0.293 R☉

Stellar Mass

0.290 M☉

Metallicity [Fe/H]

0.09

Extended Stellar Properties

Surface gravity (log g)

4.909 dex

Stellar density

13.194 g/cm³

Systemic radial velocity

18.41 km/s

Rotation period

99.00 days

Metallicity ratio

[Fe/H]

Distance

5.92 parsec

Light-years 19.31 ly

V-band magnitude

9.84 mag

Voyager-speed travel 340,593 yr

Multi-band Host Photometry — 7 bands

Astrometric Data

Parallax

263.260 mas

Total Proper Motion

3,737.871 mas/yr

PM Right Ascension

571.00 mas/yr

PM Declination

-3,694.00 mas/yr

Galactic Cartesian (pc)

x = -0.371 · y = 0.924 · z = 0.091

Equatorial (J2000)

RA 111.85209° · Dec 5.22581°

Galactic ℓ, b

212.345° · 10.374°

Ecliptic λ, β

112.739° · -16.505°

HTM-20 index

2030309745