Key parameters at a glance

A radius of 3.04 Earth radii
A mass of 9.51 Earth masses
Surface gravity around 1.03 g
An orbital period of 3.364 days
Semi-major axis 0.0348 AU
Equilibrium temperature 1,722 K (1449 °C)
Distance from Earth 373.43 light-years
Earth Similarity Index 0.124
Travel time at Voyager 1 speed 6,585,478 years

1 sibling around TOI-261

TOI-261.01 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-261.01 this	Sub-Neptune	3.04	9.51	3.364	1,722	2021
TOI-261.02	Sub-Neptune	3.35	11.20	13.039	1,008	2021

TOI-261.01 Planet Profile

Physical Specs

Radius

3.04 R⊕

Radius (Jupiter)

0.271 R♃

Mass

9.51 M⊕

Mass (Jupiter)

0.030 M♃

Density

1.85 g/cm³

Surface Gravity

1.03 g (Earth)

Classification

Planet Type

Sub-Neptune

ESI Score 0.124

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

#480of 1978

top 24.2%

This planet

3.04R⊕

Sub-Neptune median

2.71R⊕

Nearest-size peers

Kepler-1490 b 3.04 R⊕ Kepler-216 c 3.04 R⊕ TOI-1438 b 3.04 R⊕

Metric	Earth	TOI-261.01	Jupiter
Radius (R⊕)	1.00	3.04	11.21
Mass (M⊕)	1.00	9.51	317.83
Density (g/cm³)	5.51	1.85	1.33
Surface Gravity (g)	1.00	1.03	2.53
Insolation (S⊕)	1.00	874.80	0.037

Star Catalogue Identifiers

HIP

HIP 4739

TIC

TIC 63898957

Gaia DR2

Gaia DR2 2345033662373296768

Gaia DR3

Gaia DR3 2345033662373296768

System

TOI-261

Percentile among Sub-Neptune cohort

Radius 3.045 R⊕ · percentile 76 / cohort 1978

Mass 9.510 M⊕ · percentile 69 / cohort 1978

Orbital period 3.36 d · percentile 6 / cohort 1946

Distance 114.50 pc · percentile 23 / cohort 1975

ESI 0.124 · percentile 1 / cohort 1978

Orbit & Habitability

Orbital Dynamics

Period

3.364 days

Semi-major axis

0.0348 AU

Eccentricity

—

Inclination

— °

Year Length

A year here lasts approximately 3.36 Earth days (0.9% of a terrestrial year) at a mean orbital distance of 0.0348 AU.

Transit Fingerprint

Depth

0.042 %

Duration

3.343 h

Rp / R★

0.021788

Transit midpoint (BJD)

2,458,383.9156

Photometric dip

Transit produces a flux drop of 422 ppm lasting ≈ 3.34 h.

Extended Orbital Architecture

Planet / star radius ratio

0.021788

Semi-major axis / stellar radius

5.847

Transit mid-time (BJD)

2,458,383.9156

Angular separation (arcsec)

0.30400

Eq. Temperature

1,722K

(1449 °C)

Insolation (S⊕)

874.80

Earth = 1.00

Earth Similarity (ESI)

0.124

0 = alien, 1 = Earth-identical

Inside the inner HZ boundary (too hot for liquid water) — the dayside is scorched.

Discovery Paper

Primary reference

Giacalone et al. 2021

Instrument

TESS CCD Array

Publication

2021-01

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-261

Spectral Class

G-type yellow (Sun-like)

Effective Temperature

5,890 K — hotter than the Sun (5,778 K)

Estimated Age

—

Stellar Radius

1.280 R☉

Stellar Mass

0.497 M☉

Metallicity [Fe/H]

-0.35

Extended Stellar Properties

Surface gravity (log g)

3.920 dex

Stellar density

0.718 g/cm³

Metallicity ratio

[M/H]

Distance

114.50 parsec

Light-years 373.43 ly

V-band magnitude

9.56 mag

Voyager-speed travel 6,585,478 yr

Multi-band Host Photometry — 11 bands

Astrometric Data

Parallax

8.705 mas

Total Proper Motion

108.937 mas/yr

PM Right Ascension

108.36 mas/yr

PM Declination

-11.20 mas/yr

Galactic Cartesian (pc)

x = 0.879 · y = 0.239 · z = -0.413

Equatorial (J2000)

RA 15.21814° · Dec -24.42399°

Galactic ℓ, b

161.598° · -86.562°

Ecliptic λ, β

3.566° · -28.323°

HTM-20 index

627546212