Key parameters at a glance
- A radius of 12.53 Earth radii
- A mass of 155.42 Earth masses
- Surface gravity around 0.99 g
- An orbital period of 2.909 days
- Semi-major axis 0.0340 AU
- Equilibrium temperature 695 K (422 °C)
- Distance from Earth 504.72 light-years
- Earth Similarity Index 0.187
- Travel time at Voyager 1 speed 8,900,792 years
- Almost certainly tidally locked to its host star given the close orbit
TOI-4666 b Planet Profile
Physical Specs
Classification
Planet Type
Gas Giant
Discovery
Size rank in cohort
Rank by radius
#1230of 1771
top 69.4%
This planet
12.53R⊕
Gas Giant median
13.52R⊕
Nearest-size peers
| Metric | Earth | TOI-4666 b | Jupiter |
|---|---|---|---|
| Radius (R⊕) | 1.00 | 12.53 | 11.21 |
| Mass (M⊕) | 1.00 | 155.42 | 317.83 |
| Density (g/cm³) | 5.51 | 0.43 | 1.33 |
| Surface Gravity (g) | 1.00 | 0.99 | 2.53 |
| Insolation (S⊕) | 1.00 | 55.60 | 0.037 |
Alternative Mass Estimates
| Method | Value | Interpretation |
|---|---|---|
| Best measured mass | 155.418 M⊕ | Direct mass measurement (not derived). |
Star Catalogue Identifiers
TIC
TIC 165202476
Gaia DR2
Gaia DR2 4855422771071903232
Gaia DR3
Gaia DR3 4855422771071903232
System
TOI-4666
Percentile among Gas Giant cohort
Orbit & Habitability
Orbital Dynamics
Year Length
A year here lasts approximately 2.91 Earth days (0.8% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0340 AU.
Transit Fingerprint
Depth
4.516 %
Duration
51.290 h
Impact parameter b
0.045
Rp / R★
0.196530
Transit midpoint (BJD)
2,460,265.1362
Photometric dip
Transit produces a flux drop of 45,160 ppm lasting ≈ 51.29 h.
Extended Orbital Architecture
Planet / star radius ratio
0.196530
Semi-major axis / stellar radius
12.450
Impact parameter (b)
0.045
RV semi-amplitude (K)
103.000 m/s
Transit mid-time (BJD)
2,460,265.1362
Long. of periastron (ω)
183.00°
Angular separation (arcsec)
0.22000
Eq. Temperature
695K
(422 °C)
Insolation (S⊕)
55.60
Earth = 1.00
Earth Similarity (ESI)
0.187
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
Frensch et al. 2025Instrument
TESS CCD Array
Publication
2025-10
Observation locale
Space
Discovery cohort
Planets confirmed in 2025 at Transiting Exoplanet Survey Satellite (TESS) (12 shown).
Host System: TOI-4666
Spectral Class
M-type red dwarf
Effective Temperature
3,793 K — cooler than the Sun (5,778 K)
Estimated Age
3.00 Gyr — younger than the Sun (4.6 Gyr)
Stellar Radius
0.585 R☉
Stellar Mass
0.576 M☉
Metallicity [Fe/H]
0.79
Extended Stellar Properties
Surface gravity (log g)
4.664 dex
Stellar density
4.380 g/cm³
Rotation period
15.30 days
Metallicity ratio
[Fe/H]
Multi-band Host Photometry — 11 bands
Astrometric Data
Parallax
6.433 mas
Total Proper Motion
22.476 mas/yr
PM Right Ascension
4.11 mas/yr
PM Declination
-22.10 mas/yr
Galactic Cartesian (pc)
x = 0.431 · y = 0.646 · z = -0.630
Equatorial (J2000)
RA 56.28989° · Dec -39.06318°
Galactic ℓ, b
242.573° · -52.109°
Ecliptic λ, β
38.427° · -56.626°
HTM-20 index
52575270
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