Key parameters at a glance
- A radius of 2.12 Earth radii
- A mass of 6.80 Earth masses
- Surface gravity around 1.51 g
- An orbital period of 5.800 days
- Semi-major axis 0.0377 AU
- Equilibrium temperature 384 K (111 °C)
- Distance from Earth 104.94 light-years
- Earth Similarity Index 0.638
- Travel time at Voyager 1 speed 1,850,658 years
- Almost certainly tidally locked to its host star given the close orbit
TOI-2120 b Planet Profile
Physical Specs
Classification
Planet Type
Sub-Neptune
Discovery
Size rank in cohort
Rank by radius
#1781of 1978
top 90.0%
This planet
2.12R⊕
Sub-Neptune median
2.71R⊕
Nearest-size peers
| Metric | Earth | TOI-2120 b | Jupiter |
|---|---|---|---|
| Radius (R⊕) | 1.00 | 2.12 | 11.21 |
| Mass (M⊕) | 1.00 | 6.80 | 317.83 |
| Density (g/cm³) | 5.51 | — | 1.33 |
| Surface Gravity (g) | 1.00 | 1.51 | 2.53 |
| Insolation (S⊕) | 1.00 | 3.61 | 0.037 |
Alternative Mass Estimates
| Method | Value | Interpretation |
|---|---|---|
| Best measured mass | 6.800 M⊕ | Direct mass measurement (not derived). |
Star Catalogue Identifiers
TIC
TIC 389900760
Gaia DR2
Gaia DR2 513299860904522752
Gaia DR3
Gaia DR3 513299860904522752
System
TOI-2120
Percentile among Sub-Neptune cohort
Orbit & Habitability
Orbital Dynamics
Year Length
A year here lasts approximately 5.80 Earth days (1.6% of a terrestrial year) on a highly eccentric trajectory at a mean orbital distance of 0.0377 AU.
Transit Fingerprint
Depth
0.857 %
Duration
1.014 h
Impact parameter b
0.550
Rp / R★
0.079600
Transit midpoint (BJD)
2,458,795.8237
Photometric dip
Transit produces a flux drop of 8,567 ppm lasting ≈ 1.01 h.
Extended Orbital Architecture
Planet / star radius ratio
0.079600
Semi-major axis / stellar radius
33.210
Impact parameter (b)
0.550
RV semi-amplitude (K)
7.300 m/s
Transit mid-time (BJD)
2,458,795.8237
Angular separation (arcsec)
1.17000
Eq. Temperature
384K
(111 °C)
Insolation (S⊕)
3.61
Earth = 1.00
Earth Similarity (ESI)
0.638
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
Hori et al. 2024Instrument
TESS CCD Array
Publication
2024-06
Observation locale
Space
Discovery cohort
Planets confirmed in 2024 at Transiting Exoplanet Survey Satellite (TESS) (12 shown).
Host System: TOI-2120
Spectral Class
M-type red dwarf
Effective Temperature
3,131 K — cooler than the Sun (5,778 K)
Estimated Age
—
Stellar Radius
0.245 R☉
Stellar Mass
0.211 M☉
Metallicity [Fe/H]
0.39
Extended Stellar Properties
Surface gravity (log g)
4.985 dex
Stellar density
20.600 g/cm³
Systemic radial velocity
20.90 km/s
Metallicity ratio
[Fe/H]
Multi-band Host Photometry — 7 bands
Astrometric Data
Parallax
31.051 mas
Total Proper Motion
374.516 mas/yr
PM Right Ascension
306.28 mas/yr
PM Declination
-215.53 mas/yr
Galactic Cartesian (pc)
x = 0.380 · y = 0.165 · z = 0.910
Equatorial (J2000)
RA 23.50732° · Dec 65.51399°
Galactic ℓ, b
127.330° · 3.007°
Ecliptic λ, β
53.498° · 50.283°
HTM-20 index
-627143816
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