Key parameters at a glance

A radius of 2.00 Earth radii
A mass of 4.20 Earth masses
Surface gravity around 1.05 g
An orbital period of 11.382 days
Semi-major axis 0.0721 AU
Equilibrium temperature 383 K (110 °C)
Distance from Earth 73.32 light-years
Earth Similarity Index 0.667
Travel time at Voyager 1 speed 1,292,956 years
Almost certainly tidally locked to its host star given the close orbit

Context from the literature

TOI-270, also known as L 231-32, is a red dwarf star 73.3 light-years away in the constellation Pictor. It has about 39% the mass and 38% the radius of the Sun, and a temperature of about 3,506 K. TOI-270 hosts a system of three known exoplanets.

Excerpted from Wikipedia · full article

2 siblings around TOI-270

TOI-270 d shares its host star with 2 other confirmed planets. Side-by-side measurements below.

Planet	Type	Radius (R⊕)	Mass (M⊕)	Period (d)	Eq. T (K)	Year
TOI-270 b	Super-Earth	1.28	1.48	3.360	600	2019
TOI-270 c	Sub-Neptune	2.33	6.20	5.661	489	2019
TOI-270 d this	Sub-Neptune	2.00	4.20	11.382	383	2019

TOI-270 d Planet Profile

Physical Specs

Radius

2.00 R⊕

Radius (Jupiter)

0.178 R♃

Mass

4.20 M⊕

Mass (Jupiter)

0.013 M♃

Density

2.90 g/cm³

Surface Gravity

1.05 g (Earth)

Classification

Planet Type

Sub-Neptune

ESI Score 0.667

HZ Position Inner

Controversial No

Discovery

Year 2019

Method Transit

Facility Transiting Exoplanet Survey Satellite (TESS)

Telescope 0.1 m TESS Telescope

Size rank in cohort

Rank by radius

#1955of 1978

top 98.8%

This planet

2.00R⊕

Sub-Neptune median

2.71R⊕

Nearest-size peers

Kepler-32 c 2.00 R⊕ Kepler-238 f 2.00 R⊕ Kepler-242 c 2.00 R⊕

Metric	Earth	TOI-270 d	Jupiter
Radius (R⊕)	1.00	2.00	11.21
Mass (M⊕)	1.00	4.20	317.83
Density (g/cm³)	5.51	2.90	1.33
Surface Gravity (g)	1.00	1.05	2.53
Insolation (S⊕)	1.00	9.21	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	4.200 M⊕	Direct mass measurement (not derived).

Star Catalogue Identifiers

TIC

TIC 259377017

Gaia DR2

Gaia DR2 4781196115469953024

Gaia DR3

Gaia DR3 4781196115469953024

System

TOI-270

Percentile among Sub-Neptune cohort

Radius 2.000 R⊕ · percentile 0 / cohort 1978

Mass 4.200 M⊕ · percentile 2 / cohort 1978

Orbital period 11.38 d · percentile 39 / cohort 1946

Distance 22.48 pc · percentile 5 / cohort 1975

ESI 0.667 · percentile 90 / cohort 1978

Orbit & Habitability

Orbital Dynamics

Period

11.382 days

Semi-major axis

0.0721 AU

Eccentricity

0.007

Inclination

89.68 °

Year Length

A year here lasts approximately 11.38 Earth days (3.1% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0721 AU.

Transit Fingerprint

Depth

0.265 %

Duration

2.117 h

Impact parameter b

0.230

Rp / R★

0.049100

Transit midpoint (BJD)

2,458,469.3382

Photometric dip

Transit produces a flux drop of 2,645 ppm lasting ≈ 2.12 h.

Extended Orbital Architecture

Planet / star radius ratio

0.049100

Semi-major axis / stellar radius

41.744

Impact parameter (b)

0.230

RV semi-amplitude (K)

2.560 m/s

Transit mid-time (BJD)

2,458,469.3382

Long. of periastron (ω)

-6.00°

Angular separation (arcsec)

3.21000

Eq. Temperature

383K

(110 °C)

Insolation (S⊕)

9.21

Earth = 1.00

Earth Similarity (ESI)

0.667

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

G Uuml Nther et al. 2019

Instrument

TESS CCD Array

Publication

2019-07

Observation locale

Space

Discovery cohort

Planets confirmed in 2019 at Transiting Exoplanet Survey Satellite (TESS) (12 shown).

LP 791-18 c · Sub-Neptune LTT 1445 A b · Super-Earth L 98-59 d · Super-Earth GJ 357 b · Rocky Terrestrial GJ 143 b · Sub-Neptune HD 23472 c · Super-Earth L 98-59 c · Super-Earth LP 791-18 b · Rocky Terrestrial TOI-270 c · Sub-Neptune HD 23472 b · Sub-Neptune TOI-270 b · Super-Earth L 98-59 b · Rocky Terrestrial

Host System: TOI-270

Spectral Class

M-type red dwarf

Effective Temperature

3,506 K — cooler than the Sun (5,778 K)

Estimated Age

—

Stellar Radius

0.380 R☉

Stellar Mass

0.386 M☉

Metallicity [Fe/H]

-0.17

Extended Stellar Properties

Surface gravity (log g)

4.872 dex

Stellar density

10.630 g/cm³

Metallicity ratio

[Fe/H]

Distance

22.48 parsec

Light-years 73.32 ly

V-band magnitude

12.60 mag

Voyager-speed travel 1,292,956 yr

Multi-band Host Photometry — 14 bands

Astrometric Data

Parallax

44.457 mas

Total Proper Motion

282.219 mas/yr

PM Right Ascension

82.94 mas/yr

PM Declination

-269.76 mas/yr

Galactic Cartesian (pc)

x = 0.227 · y = 0.573 · z = -0.788

Equatorial (J2000)

RA 68.41608° · Dec -51.95739°

Galactic ℓ, b

259.774° · -42.014°

Ecliptic λ, β

43.142° · -71.898°

HTM-20 index

224185686

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