Key parameters at a glance

A radius of 0.98 Earth radii
A mass of 0.91 Earth masses
Surface gravity around 0.94 g
An orbital period of 4.965 days
Semi-major axis 0.0400 AU
Equilibrium temperature 463 K (190 °C)
Distance from Earth 64.83 light-years
Earth Similarity Index 0.683
Travel time at Voyager 1 speed 1,143,347 years
Almost certainly tidally locked to its host star given the close orbit

Context from the literature

LHS 1678 (TOI-696) is an astrometric binary star system, located about 65 light-years from the Earth in the constellation Caelum. It is made up of a red dwarf and a companion star whose nature is still uncertain, but is likely to be a brown dwarf. The red dwarf star is known to host three small, close-in exoplanets.

Excerpted from Wikipedia · full article

2 siblings around LHS 1678

LHS 1678 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
LHS 1678 b	Rocky Terrestrial	0.69	0.35	0.860	830	2021
LHS 1678 c	Rocky Terrestrial	0.94	1.40	3.694	511	2021
LHS 1678 d this	Rocky Terrestrial	0.98	0.91	4.965	463	2024

LHS 1678 d Planet Profile

Physical Specs

Radius

0.98 R⊕

Radius (Jupiter)

0.088 R♃

Mass

0.91 M⊕

Mass (Jupiter)

0.003 M♃

Density

5.28 g/cm³

Surface Gravity

0.94 g (Earth)

Classification

Planet Type

Rocky Terrestrial

ESI Score 0.683

HZ Position Inner

Controversial No

Discovery

Year 2024

Method Transit

Facility Transiting Exoplanet Survey Satellite (TESS)

Telescope 0.1 m TESS Telescope

Size rank in cohort

Rank by radius

#354of 570

top 61.9%

This planet

0.98R⊕

Rocky Terrestrial median

1.01R⊕

Nearest-size peers

Kepler-1328 b 0.98 R⊕ Kepler-220 d 0.98 R⊕ Kepler-1053 b 0.98 R⊕

Metric	Earth	LHS 1678 d	Jupiter
Radius (R⊕)	1.00	0.98	11.21
Mass (M⊕)	1.00	0.91	317.83
Density (g/cm³)	5.51	5.28	1.33
Surface Gravity (g)	1.00	0.94	2.53
Insolation (S⊕)	1.00	9.10	0.037

Star Catalogue Identifiers

TIC

TIC 77156829

Gaia DR2

Gaia DR2 4864160624337973248

Gaia DR3

Gaia DR3 4864160624337973248

System

LHS 1678

Percentile among Rocky Terrestrial cohort

Radius 0.981 R⊕ · percentile 38 / cohort 570

Mass 0.907 M⊕ · percentile 33 / cohort 570

Orbital period 4.97 d · percentile 54 / cohort 567

Distance 19.88 pc · percentile 9 / cohort 566

ESI 0.683 · percentile 82 / cohort 570

Orbit & Habitability

Orbital Dynamics

Period

4.965 days

Semi-major axis

0.0400 AU

Eccentricity

0.036

Inclination

88.31 °

Year Length

A year here lasts approximately 4.97 Earth days (1.4% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0400 AU.

Transit Fingerprint

Depth

0.063 %

Duration

1.000 h

Impact parameter b

0.760

Rp / R★

0.027300

Transit midpoint (BJD)

2,459,000.4581

Photometric dip

Transit produces a flux drop of 633 ppm lasting ≈ 1.00 h.

Extended Orbital Architecture

Planet / star radius ratio

0.027300

Semi-major axis / stellar radius

26.010

Impact parameter (b)

0.760

Transit mid-time (BJD)

2,459,000.4581

Long. of periastron (ω)

23.00°

Angular separation (arcsec)

2.01000

Eq. Temperature

463K

(190 °C)

Insolation (S⊕)

9.10

Earth = 1.00

Earth Similarity (ESI)

0.683

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.

Discovery Paper

Primary reference

Silverstein et al. 2024

Instrument

TESS CCD Array

Publication

2024-02

Observation locale

Space

Discovery cohort

Planets confirmed in 2024 at Transiting Exoplanet Survey Satellite (TESS) (12 shown).

Gliese 12 b · Rocky Terrestrial TOI-6002 b · Super-Earth TOI-5713 b · Super-Earth TOI-4336 A b · Sub-Neptune TOI-406.01 · Sub-Neptune TOI-1224 c · Sub-Neptune TOI-2088 b · Sub-Neptune TOI-2120 b · Sub-Neptune TOI-1806.01 · Sub-Neptune TOI-4633 c · Sub-Neptune TOI-260 b · Super-Earth TOI-663 d · Super-Earth

Host System: LHS 1678

Spectral Class

M-type red dwarf

Effective Temperature

3,490 K — cooler than the Sun (5,778 K)

Estimated Age

7.00 Gyr — older than the Sun (4.6 Gyr)

Stellar Radius

0.329 R☉

Stellar Mass

0.345 M☉

Metallicity [Fe/H]

—

Extended Stellar Properties

Surface gravity (log g)

4.890 dex

Stellar density

13.900 g/cm³

Systemic radial velocity

11.47 km/s

Rotational v·sin i

0.53 km/s

Rotation period

64.00 days

Activity index (log R'HK)

-6.087

Distance

19.88 parsec

Light-years 64.83 ly

V-band magnitude

12.60 mag

Voyager-speed travel 1,143,347 yr

Multi-band Host Photometry — 6 bands

Astrometric Data

Parallax

50.277 mas

Total Proper Motion

996.945 mas/yr

PM Right Ascension

239.41 mas/yr

PM Declination

-967.77 mas/yr

Galactic Cartesian (pc)

x = 0.286 · y = 0.713 · z = -0.640

Equatorial (J2000)

RA 68.17899° · Dec -39.79087°

Galactic ℓ, b

243.298° · -42.917°

Ecliptic λ, β

54.461° · -60.566°

HTM-20 index

1504924265

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