Key parameters at a glance

A radius of 2.05 Earth radii
A mass of 6.90 Earth masses
Surface gravity around 1.65 g
An orbital period of 15.665 days
Semi-major axis 0.1001 AU
Equilibrium temperature 420 K (147 °C)
Distance from Earth 88.62 light-years
Earth Similarity Index 0.644
Travel time at Voyager 1 speed 1,562,759 years
Almost certainly tidally locked to its host star given the close orbit

1 sibling around TOI-776

TOI-776 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
TOI-776 b	Super-Earth	1.80	5.00	8.247	520	2020
TOI-776 c this	Sub-Neptune	2.05	6.90	15.665	420	2020

TOI-776 c Planet Profile

Physical Specs

Radius

2.05 R⊕

Radius (Jupiter)

0.183 R♃

Mass

6.90 M⊕

Mass (Jupiter)

0.022 M♃

Density

4.40 g/cm³

Surface Gravity

1.65 g (Earth)

Classification

Planet Type

Sub-Neptune

ESI Score 0.644

HZ Position Inner

Controversial No

Discovery

Year 2020

Method Transit

Facility Transiting Exoplanet Survey Satellite (TESS)

Telescope 0.1 m TESS Telescope

Size rank in cohort

Rank by radius

#1901of 1978

top 96.1%

This planet

2.05R⊕

Sub-Neptune median

2.71R⊕

Nearest-size peers

LHS 1903 c 2.05 R⊕ TOI-712 b 2.05 R⊕ Kepler-363 d 2.05 R⊕

Metric	Earth	TOI-776 c	Jupiter
Radius (R⊕)	1.00	2.05	11.21
Mass (M⊕)	1.00	6.90	317.83
Density (g/cm³)	5.51	4.40	1.33
Surface Gravity (g)	1.00	1.65	2.53
Insolation (S⊕)	1.00	4.90	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	6.900 M⊕	Direct mass measurement (not derived).

Star Catalogue Identifiers

TIC

TIC 306996324

Gaia DR2

Gaia DR2 3460438662009633408

Gaia DR3

Gaia DR3 3460438662009633408

System

TOI-776

Percentile among Sub-Neptune cohort

Radius 2.047 R⊕ · percentile 4 / cohort 1978

Mass 6.900 M⊕ · percentile 39 / cohort 1978

Orbital period 15.67 d · percentile 52 / cohort 1946

Distance 27.17 pc · percentile 7 / cohort 1975

ESI 0.644 · percentile 87 / cohort 1978

Orbit & Habitability

Orbital Dynamics

Period

15.665 days

Semi-major axis

0.1001 AU

Eccentricity

0.089

Inclination

89.49 °

Year Length

A year here lasts approximately 15.67 Earth days (4.3% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.1001 AU.

Transit Fingerprint

Depth

0.118 %

Duration

2.932 h

Impact parameter b

0.350

Rp / R★

0.034400

Transit midpoint (BJD)

2,459,324.5348

Photometric dip

Transit produces a flux drop of 1,177 ppm lasting ≈ 2.93 h.

Extended Orbital Architecture

Planet / star radius ratio

0.034400

Semi-major axis / stellar radius

42.750

Impact parameter (b)

0.350

RV semi-amplitude (K)

2.650 m/s

Transit mid-time (BJD)

2,459,324.5348

Long. of periastron (ω)

7.00°

Angular separation (arcsec)

3.68000

Eq. Temperature

420K

(147 °C)

Insolation (S⊕)

4.90

Earth = 1.00

Earth Similarity (ESI)

0.644

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

Luque et al. 2021

Instrument

TESS CCD Array

Publication

2021-01

Observation locale

Space

Discovery cohort

Planets confirmed in 2020 at Transiting Exoplanet Survey Satellite (TESS) (12 shown).

TOI-700 d · Rocky Terrestrial TOI-237 b · Super-Earth TOI-700 b · Rocky Terrestrial TOI-1266 c · Super-Earth LTT 3780 c · Sub-Neptune TOI-700 c · Sub-Neptune TOI-942 c · Neptune-like TOI-776 b · Super-Earth TOI-1266 b · Sub-Neptune TOI-540 b · Rocky Terrestrial LHS 1815 b · Rocky Terrestrial TOI-122 b · Sub-Neptune

Host System: TOI-776

Spectral Class

M-type red dwarf

Effective Temperature

3,725 K — cooler than the Sun (5,778 K)

Estimated Age

6.10 Gyr — older than the Sun (4.6 Gyr)

Stellar Radius

0.547 R☉

Stellar Mass

0.542 M☉

Metallicity [Fe/H]

-0.21

Extended Stellar Properties

Surface gravity (log g)

4.800 dex

Stellar density

6.024 g/cm³

Systemic radial velocity

49.34 km/s

Rotational v·sin i

2.20 km/s

Rotation period

21.13 days

Metallicity ratio

[Fe/H]

Distance

27.17 parsec

Light-years 88.62 ly

V-band magnitude

11.54 mag

Voyager-speed travel 1,562,759 yr

Multi-band Host Photometry — 14 bands

Astrometric Data

Parallax

36.776 mas

Total Proper Motion

289.999 mas/yr

PM Right Ascension

251.11 mas/yr

PM Declination

-145.06 mas/yr

Galactic Cartesian (pc)

x = -0.793 · y = 0.020 · z = -0.609

Equatorial (J2000)

RA 178.57800° · Dec -37.55336°

Galactic ℓ, b

290.576° · 23.944°

Ecliptic λ, β

195.805° · -34.543°

HTM-20 index

-1090054726