Key parameters at a glance

A radius of 1.51 Earth radii
A mass of 2.89 Earth masses
Surface gravity around 1.27 g
An orbital period of 18.650 days
Semi-major axis 0.0911 AU
Distance from Earth 19.31 light-years
Earth Similarity Index 0.889
Travel time at Voyager 1 speed 340,593 years
Almost certainly tidally locked to its host star given the close orbit

Context from the literature

Luyten b is a confirmed exoplanet, likely rocky, orbiting within the habitable zone of the nearby red dwarf Luyten's Star. It is the fourth-closest potentially habitable exoplanet known, at a distance of 12 light-years. Only Proxima Centauri b, Ross 128 b, and GJ 1061 d are closer. Discovered alongside Gliese 273c in June 2017, Luyten b is a super-Earth of around 2.89 times the mass of Earth and receives only 6% more starlight than Earth, making it one of the best candidates for habitability.

Excerpted from Wikipedia · full article

1 sibling around GJ 273

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

GJ 273 b Planet Profile

Physical Specs

Radius

1.51 R⊕

Radius (Jupiter)

0.135 R♃

Mass

2.89 M⊕

Mass (Jupiter)

0.009 M♃

Density

4.61 g/cm³

Surface Gravity

1.27 g (Earth)

Classification

Planet Type

Super-Earth

ESI Score 0.889

HZ Position Habitable

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

#730of 1176

top 62.0%

This planet

1.51R⊕

Super-Earth median

1.60R⊕

Nearest-size peers

Kepler-249 c 1.51 R⊕ Kepler-205 b 1.51 R⊕ Kepler-389 b 1.51 R⊕

Metric	Earth	GJ 273 b	Jupiter
Radius (R⊕)	1.00	1.51	11.21
Mass (M⊕)	1.00	2.89	317.83
Density (g/cm³)	5.51	4.61	1.33
Surface Gravity (g)	1.00	1.27	2.53
Insolation (S⊕)	1.00	1.06	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Minimum mass (M sin i)	2.890 M⊕	Lower bound from radial-velocity fitting.

Star Catalogue Identifiers

HIP

HIP 36208

TIC

TIC 318686860

System

GJ 273

Percentile among Super-Earth cohort

Radius 1.510 R⊕ · percentile 37 / cohort 1176

Mass 2.890 M⊕ · percentile 34 / cohort 1176

Orbital period 18.65 d · percentile 83 / cohort 1164

Distance 5.92 pc · percentile 1 / cohort 1171

ESI 0.889 · percentile 96 / cohort 1176

Orbit & Habitability

Orbital Dynamics

Period

18.650 days

Semi-major axis

0.0911 AU

Eccentricity

0.100

Inclination

— °

Year Length

A year here lasts approximately 18.65 Earth days (5.1% of a terrestrial year) on a mildly elliptical path at a mean orbital distance of 0.0911 AU.

Eq. Temperature

—

Insolation (S⊕)

1.06

Earth = 1.00

Earth Similarity (ESI)

0.889

0 = alien, 1 = Earth-identical

Within the conservative habitable zone. 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).

GJ 273 c · Rocky Terrestrial Ross 128 b · Rocky Terrestrial GJ 3138 b · Rocky Terrestrial GJ 3323 c · Super-Earth GJ 3323 b · Rocky Terrestrial 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

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