Key parameters at a glance

A radius of 1.75 Earth radii
A mass of 4.64 Earth masses
Surface gravity around 1.51 g
An orbital period of 3.238 days
Semi-major axis 0.0370 AU
Equilibrium temperature 873 K (600 °C)
Distance from Earth 204.50 light-years
Earth Similarity Index 0.336
Travel time at Voyager 1 speed 3,606,296 years
Almost certainly tidally locked to its host star given the close orbit

5 siblings around TOI-178

TOI-178 c shares its host star with 5 other confirmed planets. Side-by-side measurements below.

Planet	Type	Radius (R⊕)	Mass (M⊕)	Period (d)	Eq. T (K)	Year
TOI-178 b	Rocky Terrestrial	1.20	0.96	1.915	1,040	2021
TOI-178 c this	Super-Earth	1.75	4.64	3.238	873	2021
TOI-178 d	Sub-Neptune	2.70	5.20	6.558	690	2021
TOI-178 e	Sub-Neptune	2.30	3.48	9.963	600	2021
TOI-178 f	Sub-Neptune	2.42	5.63	15.233	521	2021
TOI-178 g	Sub-Neptune	2.94	4.40	20.717	470	2021

TOI-178 c Planet Profile

Physical Specs

Radius

1.75 R⊕

Radius (Jupiter)

0.156 R♃

Mass

4.64 M⊕

Mass (Jupiter)

0.015 M♃

Density

4.80 g/cm³

Surface Gravity

1.51 g (Earth)

Classification

Planet Type

Super-Earth

ESI Score 0.336

HZ Position Inner

Controversial No

Discovery

Year 2021

Method Transit

Facility Transiting Exoplanet Survey Satellite (TESS)

Telescope 0.1 m TESS Telescope

Size rank in cohort

Rank by radius

#325of 1176

top 27.6%

This planet

1.75R⊕

Super-Earth median

1.60R⊕

Nearest-size peers

Kepler-301 d 1.75 R⊕ Kepler-1243 b 1.75 R⊕ Kepler-122 f 1.75 R⊕

Metric	Earth	TOI-178 c	Jupiter
Radius (R⊕)	1.00	1.75	11.21
Mass (M⊕)	1.00	4.64	317.83
Density (g/cm³)	5.51	4.80	1.33
Surface Gravity (g)	1.00	1.51	2.53
Insolation (S⊕)	1.00	97.62	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	4.640 M⊕	Direct mass measurement (not derived).

Star Catalogue Identifiers

TIC

TIC 251848941

Gaia DR2

Gaia DR2 2318295979126499200

Gaia DR3

Gaia DR3 2318295979126499200

System

TOI-178

Percentile among Super-Earth cohort

Radius 1.754 R⊕ · percentile 72 / cohort 1176

Mass 4.640 M⊕ · percentile 91 / cohort 1176

Orbital period 3.24 d · percentile 24 / cohort 1164

Distance 62.70 pc · percentile 13 / cohort 1171

ESI 0.336 · percentile 47 / cohort 1176

Orbit & Habitability

Orbital Dynamics

Period

3.238 days

Semi-major axis

0.0370 AU

Eccentricity

0.000

Inclination

88.40 °

Year Length

A year here lasts approximately 3.24 Earth days (0.9% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0370 AU.

Transit Fingerprint

Depth

0.059 %

Duration

1.950 h

Impact parameter b

0.394

Rp / R★

0.024310

Transit midpoint (BJD)

2,458,356.1075

Photometric dip

Transit produces a flux drop of 591 ppm lasting ≈ 1.95 h.

Extended Orbital Architecture

Planet / star radius ratio

0.024310

Semi-major axis / stellar radius

12.230

Impact parameter (b)

0.394

RV semi-amplitude (K)

2.770 m/s

Transit mid-time (BJD)

2,458,356.1075

Long. of periastron (ω)

26.00°

Angular separation (arcsec)

0.59000

Eq. Temperature

873K

(600 °C)

Insolation (S⊕)

97.62

Earth = 1.00

Earth Similarity (ESI)

0.336

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.

Detection Signatures

Transit photometry

A transit dip has been observed from at least one telescope.

Radial velocity

Stellar wobble has been measured spectroscopically.

Discovery Paper

Primary reference

Leleu et al. 2021

Instrument

TESS CCD Array

Publication

2021-05

Observation locale

Space

Discovery cohort

Planets confirmed in 2021 at Transiting Exoplanet Survey Satellite (TESS) (12 shown).

TOI-2257 b · Sub-Neptune TOI-2285 b · Super-Earth TOI-1231 b · Sub-Neptune AU Mic c · Sub-Neptune LHS 1678 c · Rocky Terrestrial LHS 1478 b · Rocky Terrestrial TOI-2406 b · Sub-Neptune HD 207897 b · Sub-Neptune TOI-269 b · Sub-Neptune TIC 172900988 b · Gas Giant TOI-178 g · Sub-Neptune TOI-2076 d · Sub-Neptune

Host System: TOI-178

Spectral Class

K-type orange

Effective Temperature

4,316 K — cooler than the Sun (5,778 K)

Estimated Age

6.00 Gyr — older than the Sun (4.6 Gyr)

Stellar Radius

0.662 R☉

Stellar Mass

0.647 M☉

Metallicity [Fe/H]

-0.23

Extended Stellar Properties

Surface gravity (log g)

4.450 dex

Stellar density

3.144 g/cm³

Systemic radial velocity

57.38 km/s

Rotational v·sin i

1.50 km/s

Metallicity ratio

[Fe/H]

Distance

62.70 parsec

Light-years 204.50 ly

V-band magnitude

11.96 mag

Voyager-speed travel 3,606,296 yr

Multi-band Host Photometry — 11 bands

Astrometric Data

Parallax

15.921 mas

Total Proper Motion

173.491 mas/yr

PM Right Ascension

149.95 mas/yr

PM Declination

-87.25 mas/yr

Galactic Cartesian (pc)

x = 0.855 · y = 0.110 · z = -0.507

Equatorial (J2000)

RA 7.30201° · Dec -30.45412°

Galactic ℓ, b

357.289° · -84.104°

Ecliptic λ, β

353.254° · -30.571°

HTM-20 index

-1735222970

Similar Worlds

Kepler-245 e

Super-Earth · K-type orange

Radius 1.75 R⊕ · 2,809.9 ly

Kepler-124 c

Super-Earth · K-type orange

Radius 1.75 R⊕ · 1,370.0 ly

K2-216 b

Super-Earth · K-type orange

Radius 1.75 R⊕ · 376.6 ly

Kepler-1062 b

Super-Earth · K-type orange

Radius 1.76 R⊕ · 1,296.3 ly

Kepler-1814 c

Super-Earth · K-type orange

Radius 1.76 R⊕ · 2,369.0 ly

Kepler-755 b

Super-Earth · K-type orange

Radius 1.76 R⊕ · 1,301.5 ly

Explore Related Categories

Super-Earth Planets Transit Discoveries Transiting Exoplanet Survey Satellite (TESS) Mission K-type orange Hosts