Key parameters at a glance
- A radius of 2.96 Earth radii
- A mass of 9.04 Earth masses
- Surface gravity around 1.04 g
- An orbital period of 4.783 days
- Semi-major axis 0.0535 AU
- Equilibrium temperature 886 K (613 °C)
- Distance from Earth 2,125.83 light-years
- Earth Similarity Index 0.267
- Travel time at Voyager 1 speed 37,488,999 years
- Almost certainly tidally locked to its host star given the close orbit
Kepler-1728 b Planet Profile
Physical Specs
Classification
Planet Type
Sub-Neptune
Discovery
Size rank in cohort
Rank by radius
#553of 1978
top 27.9%
This planet
2.96R⊕
Sub-Neptune median
2.71R⊕
Nearest-size peers
| Metric | Earth | Kepler-1728 b | Jupiter |
|---|---|---|---|
| Radius (R⊕) | 1.00 | 2.96 | 11.21 |
| Mass (M⊕) | 1.00 | 9.04 | 317.83 |
| Density (g/cm³) | 5.51 | 1.93 | 1.33 |
| Surface Gravity (g) | 1.00 | 1.04 | 2.53 |
| Insolation (S⊕) | 1.00 | 145.48 | 0.037 |
Star Catalogue Identifiers
TIC
TIC 121085785
Gaia DR2
Gaia DR2 2100378478222060032
Gaia DR3
Gaia DR3 2100378478222060032
System
Kepler-1728
Percentile among Sub-Neptune cohort
Orbit & Habitability
Orbital Dynamics
Year Length
A year here lasts approximately 4.78 Earth days (1.3% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0535 AU.
Transit Fingerprint
Depth
0.101 %
Duration
2.379 h
Impact parameter b
0.003
Rp / R★
0.028315
Transit midpoint (BJD)
2,455,003.5084
Photometric dip
Transit produces a flux drop of 1,009 ppm lasting ≈ 2.38 h.
Extended Orbital Architecture
Planet / star radius ratio
0.028315
Semi-major axis / stellar radius
16.102
Impact parameter (b)
0.003
Transit mid-time (BJD)
2,455,003.5084
Angular separation (arcsec)
0.08210
Eq. Temperature
886K
(613 °C)
Insolation (S⊕)
145.48
Earth = 1.00
Earth Similarity (ESI)
0.267
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
Valizadegan et al. 2022Instrument
Kepler CCD Array
Publication
2022-02
Observation locale
Space
Discovery cohort
Planets confirmed in 2021 at Kepler (12 shown).
Host System: Kepler-1728
Spectral Class
K-type orange
Effective Temperature
5,170 K — cooler than the Sun (5,778 K)
Estimated Age
12.80 Gyr — older than the Sun (4.6 Gyr)
Stellar Radius
0.807 R☉
Stellar Mass
0.891 M☉
Metallicity [Fe/H]
0.18
Extended Stellar Properties
Surface gravity (log g)
4.574 dex
Stellar density
3.452 g/cm³
Metallicity ratio
[Fe/H]
Multi-band Host Photometry — 17 bands
Astrometric Data
Parallax
1.506 mas
Total Proper Motion
5.262 mas/yr
PM Right Ascension
2.26 mas/yr
PM Declination
4.75 mas/yr
Galactic Cartesian (pc)
x = 0.228 · y = -0.742 · z = 0.630
Equatorial (J2000)
RA 287.09400° · Dec 39.06078°
Galactic ℓ, b
70.094° · 13.669°
Ecliptic λ, β
297.940° · 60.852°
HTM-20 index
-556013328
Similar Worlds
TOI-2459 b
Sub-Neptune · K-type orange
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K2-270 c
Sub-Neptune · K-type orange
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Kepler-735 b
Sub-Neptune · K-type orange
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Kepler-993 b
Sub-Neptune · K-type orange
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TOI-815 b
Sub-Neptune · K-type orange
Radius 2.94 R⊕ · 194.8 ly
Kepler-1086 c
Sub-Neptune · K-type orange
Radius 2.94 R⊕ · 1,520.2 ly