Key parameters at a glance
- A radius of 2.33 Earth radii
- A mass of 7.70 Earth masses
- Surface gravity around 1.42 g
- An orbital period of 4.659 days
- Equilibrium temperature 450 K (177 °C)
- Distance from Earth 140.86 light-years
- Earth Similarity Index 0.574
- Travel time at Voyager 1 speed 2,483,984 years
- Almost certainly tidally locked to its host star given the close orbit
TOI-1243 b Planet Profile
Physical Specs
Classification
Planet Type
Sub-Neptune
Discovery
Size rank in cohort
Rank by radius
#1451of 1978
top 73.3%
This planet
2.33R⊕
Sub-Neptune median
2.71R⊕
Nearest-size peers
| Metric | Earth | TOI-1243 b | Jupiter |
|---|---|---|---|
| Radius (R⊕) | 1.00 | 2.33 | 11.21 |
| Mass (M⊕) | 1.00 | 7.70 | 317.83 |
| Density (g/cm³) | 5.51 | 3.30 | 1.33 |
| Surface Gravity (g) | 1.00 | 1.42 | 2.53 |
| Insolation (S⊕) | 1.00 | 17.27 | 0.037 |
Alternative Mass Estimates
| Method | Value | Interpretation |
|---|---|---|
| Best measured mass | 7.700 M⊕ | Direct mass measurement (not derived). |
Star Catalogue Identifiers
TIC
TIC 219698776
Gaia DR2
Gaia DR2 1119059574424538496
Gaia DR3
Gaia DR3 1119059574424538496
System
TOI-1243
Percentile among Sub-Neptune cohort
Orbit & Habitability
Orbital Dynamics
Year Length
A year here lasts approximately 4.66 Earth days (1.3% of a terrestrial year).
Transit Fingerprint
Depth
0.173 %
Duration
0.901 h
Impact parameter b
0.780
Rp / R★
0.041800
Transit midpoint (BJD)
2,459,369.8310
Photometric dip
Transit produces a flux drop of 1,725 ppm lasting ≈ 0.90 h.
Extended Orbital Architecture
Planet / star radius ratio
0.041800
Semi-major axis / stellar radius
25.500
Impact parameter (b)
0.780
RV semi-amplitude (K)
4.600 m/s
Transit mid-time (BJD)
2,459,369.8310
Eq. Temperature
450K
(177 °C)
Insolation (S⊕)
17.27
Earth = 1.00
Earth Similarity (ESI)
0.574
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.
Discovery Paper
Primary reference
Poultourtzidis et al. 2026Instrument
TESS CCD Array
Publication
2026-01
Observation locale
Space
Discovery cohort
Planets confirmed in 2026 at Transiting Exoplanet Survey Satellite (TESS) (12 shown).
Host System: TOI-1243
Spectral Class
M-type red dwarf
Effective Temperature
3,515 K — cooler than the Sun (5,778 K)
Estimated Age
—
Stellar Radius
0.511 R☉
Stellar Mass
0.515 M☉
Metallicity [Fe/H]
-0.20
Extended Stellar Properties
Surface gravity (log g)
4.730 dex
Stellar density
5.400 g/cm³
Rotational v·sin i
2.00 km/s
Metallicity ratio
[Fe/H]
Multi-band Host Photometry — 11 bands
Astrometric Data
Parallax
23.127 mas
Total Proper Motion
174.684 mas/yr
PM Right Ascension
-100.40 mas/yr
PM Declination
-142.95 mas/yr
Galactic Cartesian (pc)
x = -0.226 · y = 0.220 · z = 0.949
Equatorial (J2000)
RA 135.73264° · Dec 71.63642°
Galactic ℓ, b
141.972° · 35.800°
Ecliptic λ, β
111.275° · 51.563°
HTM-20 index
831173694
Similar Worlds
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Sub-Neptune · M-type red dwarf
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