Key parameters at a glance
- A radius of 4.60 Earth radii
- A mass of 19.20 Earth masses
- Surface gravity around 0.91 g
- An orbital period of 34.005 days
- Semi-major axis 0.1136 AU
- Equilibrium temperature 204 K (-69 °C)
- Distance from Earth 125.91 light-years
- Earth Similarity Index 0.459
- Travel time at Voyager 1 speed 2,220,507 years
- Almost certainly tidally locked to its host star given the close orbit
Context from the literature
TOI-6478b is a cold under-dense Neptune-like exoplanet that orbits around TOI-6478, a M-type main sequence star located 126 light years from Earth in the constellation of Hydra. It has a mass of 9.9 Earth masses and a radius of 4.6 Earth radii. The planet orbital period is 34.005019 days.
Excerpted from Wikipedia · full article
TOI-6478 b Planet Profile
Physical Specs
Classification
Planet Type
Neptune-like
Discovery
Size rank in cohort
Rank by radius
#446of 574
top 77.5%
This planet
4.60R⊕
Neptune-like median
6.39R⊕
Nearest-size peers
| Metric | Earth | TOI-6478 b | Jupiter |
|---|---|---|---|
| Radius (R⊕) | 1.00 | 4.60 | 11.21 |
| Mass (M⊕) | 1.00 | 19.20 | 317.83 |
| Density (g/cm³) | 5.51 | 1.08 | 1.33 |
| Surface Gravity (g) | 1.00 | 0.91 | 2.53 |
| Insolation (S⊕) | 1.00 | 0.00 | 0.037 |
Star Catalogue Identifiers
TIC
TIC 332657786
Gaia DR2
Gaia DR2 5673934548598976256
Gaia DR3
Gaia DR3 5673934548598976256
System
TOI-6478
Percentile among Neptune-like cohort
Orbit & Habitability
Orbital Dynamics
Year Length
A year here lasts approximately 34.01 Earth days (9.3% of a terrestrial year) at a mean orbital distance of 0.1136 AU.
Transit Fingerprint
Depth
3.421 %
Duration
2.900 h
Impact parameter b
0.186
Rp / R★
0.180270
Transit midpoint (BJD)
2,459,454.9010
Photometric dip
Transit produces a flux drop of 34,206 ppm lasting ≈ 2.90 h.
Extended Orbital Architecture
Planet / star radius ratio
0.180270
Semi-major axis / stellar radius
104.400
Impact parameter (b)
0.186
Transit mid-time (BJD)
2,459,454.9010
Angular separation (arcsec)
2.94000
Eq. Temperature
204K
(-69 °C)
Insolation (S⊕)
0.00
Earth = 1.00
Earth Similarity (ESI)
0.459
0 = alien, 1 = Earth-identical
Beyond the outer HZ boundary (too cold) — surface water would be frozen. Close-orbiting tidally-locked around a cool host.
Discovery Paper
Primary reference
Scott et al. 2025Instrument
TESS CCD Array
Publication
2025-04
Observation locale
Space
Discovery cohort
Planets confirmed in 2025 at Transiting Exoplanet Survey Satellite (TESS) (12 shown).
Host System: TOI-6478
Spectral Class
M-type red dwarf
Effective Temperature
3,230 K — cooler than the Sun (5,778 K)
Estimated Age
6.00 Gyr — older than the Sun (4.6 Gyr)
Stellar Radius
0.234 R☉
Stellar Mass
0.230 M☉
Metallicity [Fe/H]
-0.53
Extended Stellar Properties
Surface gravity (log g)
5.016 dex
Stellar density
18.610 g/cm³
Metallicity ratio
[Fe/H]
Multi-band Host Photometry — 10 bands
Astrometric Data
Parallax
25.874 mas
Total Proper Motion
180.108 mas/yr
PM Right Ascension
52.41 mas/yr
PM Declination
-172.31 mas/yr
Galactic Cartesian (pc)
x = -0.832 · y = 0.480 · z = -0.278
Equatorial (J2000)
RA 149.99181° · Dec -16.15979°
Galactic ℓ, b
253.966° · 29.975°
Ecliptic λ, β
158.354° · -26.515°
HTM-20 index
-430777037
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