Key parameters at a glance

A radius of 2.87 Earth radii
A mass of 5.93 Earth masses
Surface gravity around 0.72 g
An orbital period of 10.779 days
Semi-major axis 0.0889 AU
Equilibrium temperature 802 K (529 °C)
Distance from Earth 279.84 light-years
Earth Similarity Index 0.279
Travel time at Voyager 1 speed 4,934,953 years

1 sibling around TOI-561

TOI-561 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-561 b	Super-Earth	1.40	2.02	0.447	2,319	2020
TOI-561 c this	Sub-Neptune	2.87	5.93	10.779	802	2020

TOI-561 c Planet Profile

Physical Specs

Radius

2.87 R⊕

Radius (Jupiter)

0.256 R♃

Mass

5.93 M⊕

Mass (Jupiter)

0.019 M♃

Density

1.30 g/cm³

Surface Gravity

0.72 g (Earth)

Classification

Planet Type

Sub-Neptune

ESI Score 0.279

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

#670of 1978

top 33.8%

This planet

2.87R⊕

Sub-Neptune median

2.71R⊕

Nearest-size peers

Kepler-1722 b 2.87 R⊕ Kepler-58 c 2.86 R⊕ Kepler-170 c 2.86 R⊕

Metric	Earth	TOI-561 c	Jupiter
Radius (R⊕)	1.00	2.87	11.21
Mass (M⊕)	1.00	5.93	317.83
Density (g/cm³)	5.51	1.30	1.33
Surface Gravity (g)	1.00	0.72	2.53
Insolation (S⊕)	1.00	67.50	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	5.930 M⊕	Direct mass measurement (not derived).

Star Catalogue Identifiers

TIC

TIC 377064495

Gaia DR2

Gaia DR2 3850421005290172416

Gaia DR3

Gaia DR3 3850421005290172416

System

TOI-561

Percentile among Sub-Neptune cohort

Radius 2.865 R⊕ · percentile 66 / cohort 1978

Mass 5.930 M⊕ · percentile 24 / cohort 1978

Orbital period 10.78 d · percentile 37 / cohort 1946

Distance 85.80 pc · percentile 19 / cohort 1975

ESI 0.279 · percentile 23 / cohort 1978

Orbit & Habitability

Orbital Dynamics

Period

10.779 days

Semi-major axis

0.0889 AU

Eccentricity

0.023

Inclination

89.61 °

Year Length

A year here lasts approximately 10.78 Earth days (3.0% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0889 AU.

Transit Fingerprint

Depth

0.113 %

Duration

3.739 h

Impact parameter b

0.150

Rp / R★

0.031150

Transit midpoint (BJD)

2,459,238.4628

Photometric dip

Transit produces a flux drop of 1,130 ppm lasting ≈ 3.74 h.

Extended Orbital Architecture

Planet / star radius ratio

0.031150

Semi-major axis / stellar radius

22.400

Impact parameter (b)

0.150

RV semi-amplitude (K)

1.980 m/s

Transit mid-time (BJD)

2,459,238.4628

Long. of periastron (ω)

219.00°

Angular separation (arcsec)

1.04000

Eq. Temperature

802K

(529 °C)

Insolation (S⊕)

67.50

Earth = 1.00

Earth Similarity (ESI)

0.279

0 = alien, 1 = Earth-identical

Inside the inner HZ boundary (too hot for liquid water) — the surface is too hot to retain surface water.

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

Lacedelli et al. 2020

Instrument

TESS CCD Array

Publication

2020-12

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-776 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

Host System: TOI-561

Spectral Class

G-type yellow (Sun-like)

Effective Temperature

5,342 K — cooler than the Sun (5,778 K)

Estimated Age

16.10 Gyr — older than the Sun (4.6 Gyr)

Stellar Radius

0.843 R☉

Stellar Mass

0.806 M☉

Metallicity [Fe/H]

-0.41

Extended Stellar Properties

Surface gravity (log g)

4.470 dex

Stellar density

1.847 g/cm³

Systemic radial velocity

79.54 km/s

Rotational v·sin i

2.00 km/s

Activity index (log R'HK)

-5.003

Metallicity ratio

[Fe/H]

Distance

85.80 parsec

Light-years 279.84 ly

V-band magnitude

10.25 mag

Voyager-speed travel 4,934,953 yr

Multi-band Host Photometry — 11 bands

Astrometric Data

Parallax

11.627 mas

Total Proper Motion

124.664 mas/yr

PM Right Ascension

-108.43 mas/yr

PM Declination

-61.51 mas/yr

Galactic Cartesian (pc)

x = -0.845 · y = 0.524 · z = 0.108

Equatorial (J2000)

RA 148.18515° · Dec 6.21610°

Galactic ℓ, b

230.849° · 42.729°

Ecliptic λ, β

148.190° · -6.265°

HTM-20 index

1626683458