Confirmed Exoplanet Discovered 2021

TOI-178 e

A sub-neptune orbiting the k-type orange TOI-178, located approximately 204.5 light-years from Earth.

Key parameters at a glance

  • A radius of 2.30 Earth radii
  • A mass of 3.48 Earth masses
  • Surface gravity around 0.66 g
  • An orbital period of 9.963 days
  • Semi-major axis 0.0783 AU
  • Equilibrium temperature 600 K (327 °C)
  • Distance from Earth 204.50 light-years
  • Earth Similarity Index 0.402
  • 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 e 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 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 this 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 e Planet Profile

Physical Specs

Radius
2.30 R⊕
Radius (Jupiter)
0.205 R♃
Mass
3.48 M⊕
Mass (Jupiter)
0.011 M♃
Density
1.58 g/cm³
Surface Gravity
0.66 g (Earth)

Classification

Planet Type

Sub-Neptune

ESI Score 0.402
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

#1498of 1978

top 75.7%

This planet

2.30R⊕

Sub-Neptune median

2.71R⊕

Nearest-size peers

K2-202 b 2.30 R⊕ Kepler-328 b 2.30 R⊕ GJ 536 c 2.30 R⊕
Metric Earth TOI-178 e Jupiter
Radius (R⊕)1.002.3011.21
Mass (M⊕)1.003.48317.83
Density (g/cm³)5.511.581.33
Surface Gravity (g)1.000.662.53
Insolation (S⊕)1.0021.820.037

Alternative Mass Estimates

Method Value Interpretation
Best measured mass 3.480 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 Sub-Neptune cohort

Radius 2.301 R⊕ · percentile 24 / cohort 1978
Mass 3.480 M⊕ · percentile 1 / cohort 1978
Orbital period 9.96 d · percentile 34 / cohort 1946
Distance 62.70 pc · percentile 14 / cohort 1975
ESI 0.402 · percentile 53 / cohort 1978

Orbit & Habitability

Orbital Dynamics

Period
9.963 days
Semi-major axis
0.0783 AU
Eccentricity
0.000
Inclination
88.71 °

Year Length

A year here lasts approximately 9.96 Earth days (2.7% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0783 AU.

Transit Fingerprint

Depth

0.102 %

Duration

2.501 h

Impact parameter b

0.574

Rp / R★

0.031910

Transit midpoint (BJD)

2,458,751.4658

Photometric dip

Transit produces a flux drop of 1,018 ppm lasting ≈ 2.50 h.

Extended Orbital Architecture

Planet / star radius ratio

0.031910

Semi-major axis / stellar radius

25.870

Impact parameter (b)

0.574

RV semi-amplitude (K)

1.620 m/s

Transit mid-time (BJD)

2,458,751.4658

Long. of periastron (ω)

2.00°

Angular separation (arcsec)

1.25000

Eq. Temperature

600K

(327 °C)

Insolation (S⊕)

21.82

Earth = 1.00

Earth Similarity (ESI)

0.402

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.

Transit timing variations

Gravitational interactions from neighbours have been detected.

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

8.513.113.06B11.96V11.15Gaia10.42TESS9.37J8.76H8.66K8.57W18.64W28.56W38.48W4

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

K2-59 c

Sub-Neptune · K-type orange

Radius 2.30 R⊕ · 1,015.4 ly

Kepler-224 d

Sub-Neptune · K-type orange

Radius 2.30 R⊕ · 2,550.8 ly

Kepler-621 b

Sub-Neptune · K-type orange

Radius 2.30 R⊕ · 1,268.7 ly

Kepler-156 b

Sub-Neptune · K-type orange

Radius 2.30 R⊕ · 1,446.4 ly

TOI-2093 c

Sub-Neptune · K-type orange

Radius 2.30 R⊕ · 270.1 ly

K2-57 b

Sub-Neptune · K-type orange

Radius 2.31 R⊕ · 861.7 ly

Explore Related Categories

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