Key parameters at a glance

A radius of 2.39 Earth radii
A mass of 8.04 Earth masses
Surface gravity around 1.41 g
An orbital period of 12.252 days
Semi-major axis 0.0757 AU
Equilibrium temperature 359 K (86 °C)
Distance from Earth 71.69 light-years
Earth Similarity Index 0.685
Travel time at Voyager 1 speed 1,264,318 years
Almost certainly tidally locked to its host star given the close orbit

Context from the literature

LTT 3780, also known as TOI-732 or LP 729-54, is the brighter component of a wide visual binary star system in the constellation Hydra. This star is host to a pair of orbiting exoplanets. Based on parallax measurements, it is located at a distance of 72 light years from the Sun. LTT 3780 has an apparent visual magnitude of 13.07, requiring a telescope to view.

Excerpted from Wikipedia · full article

1 sibling around LTT 3780

LTT 3780 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
LTT 3780 b	Super-Earth	1.33	2.46	0.768	903	2020
LTT 3780 c this	Sub-Neptune	2.39	8.04	12.252	359	2020

LTT 3780 c Planet Profile

Physical Specs

Radius

2.39 R⊕

Radius (Jupiter)

0.213 R♃

Mass

8.04 M⊕

Mass (Jupiter)

0.025 M♃

Density

3.24 g/cm³

Surface Gravity

1.41 g (Earth)

Classification

Planet Type

Sub-Neptune

ESI Score 0.685

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

#1343of 1978

top 67.8%

This planet

2.39R⊕

Sub-Neptune median

2.71R⊕

Nearest-size peers

Kepler-193 b 2.39 R⊕ Kepler-152 c 2.39 R⊕ Kepler-238 c 2.39 R⊕

Metric	Earth	LTT 3780 c	Jupiter
Radius (R⊕)	1.00	2.39	11.21
Mass (M⊕)	1.00	8.04	317.83
Density (g/cm³)	5.51	3.24	1.33
Surface Gravity (g)	1.00	1.41	2.53
Insolation (S⊕)	1.00	2.76	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	8.040 M⊕	Direct mass measurement (not derived).

Star Catalogue Identifiers

TIC

TIC 36724087

Gaia DR2

Gaia DR2 3767281845873242112

Gaia DR3

Gaia DR3 3767281845873242112

System

LTT 3780

Percentile among Sub-Neptune cohort

Radius 2.390 R⊕ · percentile 31 / cohort 1978

Mass 8.040 M⊕ · percentile 55 / cohort 1978

Orbital period 12.25 d · percentile 42 / cohort 1946

Distance 21.98 pc · percentile 5 / cohort 1975

ESI 0.685 · percentile 91 / cohort 1978

Orbit & Habitability

Orbital Dynamics

Period

12.252 days

Semi-major axis

0.0757 AU

Eccentricity

0.024

Inclination

88.96 °

Year Length

A year here lasts approximately 12.25 Earth days (3.4% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0757 AU.

Transit Fingerprint

Depth

0.336 %

Duration

1.540 h

Impact parameter b

0.794

Rp / R★

0.057900

Transit midpoint (BJD)

2,459,600.5423

Photometric dip

Transit produces a flux drop of 3,355 ppm lasting ≈ 1.54 h.

Extended Orbital Architecture

Planet / star radius ratio

0.057900

Semi-major axis / stellar radius

43.000

Impact parameter (b)

0.794

RV semi-amplitude (K)

4.220 m/s

Transit mid-time (BJD)

2,459,600.5423

Long. of periastron (ω)

-66.00°

Angular separation (arcsec)

3.44000

Eq. Temperature

359K

(86 °C)

Insolation (S⊕)

2.76

Earth = 1.00

Earth Similarity (ESI)

0.685

0 = alien, 1 = Earth-identical

Inside the inner HZ boundary (too hot for liquid water) — liquid water is physically possible with adequate atmospheric pressure. 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

Cloutier et al. 2020

Instrument

TESS CCD Array

Publication

2020-07

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 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 TOI-122 b · Sub-Neptune

Host System: LTT 3780

Spectral Class

M-type red dwarf

Effective Temperature

3,358 K — cooler than the Sun (5,778 K)

Estimated Age

3.10 Gyr — younger than the Sun (4.6 Gyr)

Stellar Radius

0.380 R☉

Stellar Mass

0.381 M☉

Metallicity [Fe/H]

0.06

Extended Stellar Properties

Surface gravity (log g)

4.850 dex

Stellar density

9.784 g/cm³

Systemic radial velocity

0.27 km/s

Rotational v·sin i

1.30 km/s

Rotation period

104.00 days

Metallicity ratio

[Fe/H]

Distance

21.98 parsec

Light-years 71.69 ly

V-band magnitude

13.14 mag

Voyager-speed travel 1,264,318 yr

Multi-band Host Photometry — 11 bands

Astrometric Data

Parallax

45.464 mas

Total Proper Motion

421.900 mas/yr

PM Right Ascension

-341.41 mas/yr

PM Declination

-247.87 mas/yr

Galactic Cartesian (pc)

x = -0.885 · y = 0.419 · z = -0.203

Equatorial (J2000)

RA 154.64490° · Dec -11.71780°

Galactic ℓ, b

254.201° · 36.305°

Ecliptic λ, β

161.040° · -20.678°

HTM-20 index

229112000

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