Key parameters at a glance

A radius of 0.89 Earth radii
A mass of 3.70 Earth masses
Surface gravity around 4.65 g
An orbital period of 7.790 days
Semi-major axis 0.0695 AU
Equilibrium temperature 701 K (428 °C)
Distance from Earth 53.23 light-years
Earth Similarity Index 0.313
Travel time at Voyager 1 speed 938,687 years
Almost certainly tidally locked to its host star given the close orbit

1 sibling around GJ 143

HD 21749 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
HD 21749 c this	Rocky Terrestrial	0.89	3.70	7.790	701	2019
GJ 143 b	Sub-Neptune	2.61	22.70	35.613	422	2019

HD 21749 c Planet Profile

Physical Specs

Radius

0.89 R⊕

Radius (Jupiter)

0.080 R♃

Mass

3.70 M⊕

Mass (Jupiter)

0.012 M♃

Density

31.93 g/cm³

Surface Gravity

4.65 g (Earth)

Classification

Planet Type

Rocky Terrestrial

ESI Score 0.313

HZ Position Inner

Controversial No

Discovery

Year 2019

Method Transit

Facility Transiting Exoplanet Survey Satellite (TESS)

Telescope 0.1 m TESS Telescope

Size rank in cohort

Rank by radius

#417of 570

top 73.0%

This planet

0.89R⊕

Rocky Terrestrial median

1.01R⊕

Nearest-size peers

Kepler-353 b 0.89 R⊕ Kepler-387 c 0.89 R⊕ Kepler-303 b 0.89 R⊕

Metric	Earth	HD 21749 c	Jupiter
Radius (R⊕)	1.00	0.89	11.21
Mass (M⊕)	1.00	3.70	317.83
Density (g/cm³)	5.51	31.93	1.33
Surface Gravity (g)	1.00	4.65	2.53
Insolation (S⊕)	1.00	305.94	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	3.700 M⊕	Direct mass measurement (not derived).

Star Catalogue Identifiers

HD 21749

HIP

HIP 16069

TIC

TIC 279741379

Gaia DR2

Gaia DR2 4673947174316727040

Gaia DR3

Gaia DR3 4673947174316727040

System

GJ 143

Percentile among Rocky Terrestrial cohort

Radius 0.892 R⊕ · percentile 27 / cohort 570

Mass 3.700 M⊕ · percentile 94 / cohort 570

Orbital period 7.79 d · percentile 72 / cohort 567

Distance 16.32 pc · percentile 8 / cohort 566

ESI 0.313 · percentile 43 / cohort 570

Orbit & Habitability

Orbital Dynamics

Period

7.790 days

Semi-major axis

0.0695 AU

Eccentricity

—

Inclination

88.90 °

Year Length

A year here lasts approximately 7.79 Earth days (2.1% of a terrestrial year) at a mean orbital distance of 0.0695 AU.

Transit Fingerprint

Depth

0.017 %

Duration

2.515 h

Impact parameter b

0.420

Rp / R★

0.011960

Transit midpoint (BJD)

2,458,371.2287

Photometric dip

Transit produces a flux drop of 169 ppm lasting ≈ 2.52 h.

Extended Orbital Architecture

Planet / star radius ratio

0.011960

Semi-major axis / stellar radius

21.800

Impact parameter (b)

0.420

RV semi-amplitude (K)

1.430 m/s

Transit mid-time (BJD)

2,458,371.2287

Angular separation (arcsec)

4.26000

Eq. Temperature

701K

(428 °C)

Insolation (S⊕)

305.94

Earth = 1.00

Earth Similarity (ESI)

0.313

0 = alien, 1 = Earth-identical

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

Discovery Paper

Primary reference

Dragomir et al. 2019

Instrument

TESS CCD Array

Publication

2019-04

Observation locale

Space

Discovery cohort

Planets confirmed in 2019 at Transiting Exoplanet Survey Satellite (TESS) (12 shown).

LP 791-18 c · Sub-Neptune LTT 1445 A b · Super-Earth TOI-270 d · Sub-Neptune L 98-59 d · Super-Earth GJ 357 b · Rocky Terrestrial GJ 143 b · Sub-Neptune HD 23472 c · Super-Earth L 98-59 c · Super-Earth LP 791-18 b · Rocky Terrestrial TOI-270 c · Sub-Neptune HD 23472 b · Sub-Neptune TOI-270 b · Super-Earth

Host System: GJ 143

Spectral Class

K-type orange

Effective Temperature

4,640 K — cooler than the Sun (5,778 K)

Estimated Age

3.80 Gyr — younger than the Sun (4.6 Gyr)

Stellar Radius

0.695 R☉

Stellar Mass

0.730 M☉

Metallicity [Fe/H]

0.00

Extended Stellar Properties

Surface gravity (log g)

4.613 dex

Stellar density

3.030 g/cm³

Systemic radial velocity

59.46 km/s

Metallicity ratio

[Fe/H]

Distance

16.32 parsec

Light-years 53.23 ly

V-band magnitude

8.08 mag

Voyager-speed travel 938,687 yr

Multi-band Host Photometry — 8 bands

Astrometric Data

Parallax

61.246 mas

Total Proper Motion

432.806 mas/yr

PM Right Ascension

355.08 mas/yr

PM Declination

-247.46 mas/yr

Galactic Cartesian (pc)

x = 0.276 · y = 0.350 · z = -0.895

Equatorial (J2000)

RA 51.75019° · Dec -63.50017°

Galactic ℓ, b

279.230° · -45.821°

Ecliptic λ, β

352.878° · -73.836°

HTM-20 index

-1611504001