Key parameters at a glance

A radius of 4.13 Earth radii
A mass of 9.20 Earth masses
Surface gravity around 0.54 g
An orbital period of 55.997 days
Semi-major axis 0.3080 AU
Equilibrium temperature 643 K (370 °C)
Distance from Earth 455.35 light-years
Earth Similarity Index 0.289
Travel time at Voyager 1 speed 8,030,091 years

2 siblings around HD 28109

HD 28109 c shares its host star with 2 other confirmed planets. Side-by-side measurements below.

Planet	Type	Radius (R⊕)	Mass (M⊕)	Period (d)	Eq. T (K)	Year
HD 28109 b	Sub-Neptune	2.69	6.20	22.891	867	2022
HD 28109 c this	Neptune-like	4.13	9.20	55.997	643	2022
HD 28109 d	Sub-Neptune	3.11	5.80	84.290	561	2022

HD 28109 c Planet Profile

Physical Specs

Radius

4.13 R⊕

Radius (Jupiter)

0.368 R♃

Mass

9.20 M⊕

Mass (Jupiter)

0.029 M♃

Density

0.70 g/cm³

Surface Gravity

0.54 g (Earth)

Classification

Planet Type

Neptune-like

ESI Score 0.289

HZ Position Inner

Controversial No

Discovery

Year 2022

Method Transit

Facility Transiting Exoplanet Survey Satellite (TESS)

Telescope 0.1 m TESS Telescope

Size rank in cohort

Rank by radius

#537of 574

top 93.4%

This planet

4.13R⊕

Neptune-like median

6.39R⊕

Nearest-size peers

Kepler-697 b 4.13 R⊕ Kepler-966 b 4.13 R⊕ Kepler-279 e 4.13 R⊕

Metric	Earth	HD 28109 c	Jupiter
Radius (R⊕)	1.00	4.13	11.21
Mass (M⊕)	1.00	9.20	317.83
Density (g/cm³)	5.51	0.70	1.33
Surface Gravity (g)	1.00	0.54	2.53
Insolation (S⊕)	1.00	29.95	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	9.200 M⊕	Direct mass measurement (not derived).

Star Catalogue Identifiers

HD 28109

HIP

HIP 20295

TIC

TIC 29781292

Gaia DR2

Gaia DR2 4668163021600295552

Gaia DR3

Gaia DR3 4668163021600295552

System

HD 28109

Percentile among Neptune-like cohort

Radius 4.130 R⊕ · percentile 6 / cohort 574

Mass 9.200 M⊕ · percentile 4 / cohort 574

Orbital period 56.00 d · percentile 73 / cohort 524

Distance 139.61 pc · percentile 31 / cohort 572

ESI 0.289 · percentile 48 / cohort 574

Orbit & Habitability

Orbital Dynamics

Period

55.997 days

Semi-major axis

0.3080 AU

Eccentricity

0.004

Inclination

89.61 °

Year Length

A year here lasts approximately 56.00 Earth days (15.3% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.3080 AU.

Transit Fingerprint

Depth

0.072 %

Duration

8.957 h

Impact parameter b

0.310

Rp / R★

0.026320

Transit midpoint (BJD)

2,458,337.2807

Photometric dip

Transit produces a flux drop of 715 ppm lasting ≈ 8.96 h.

Extended Orbital Architecture

Planet / star radius ratio

0.026320

Semi-major axis / stellar radius

46.700

Impact parameter (b)

0.310

RV semi-amplitude (K)

1.350 m/s

Transit mid-time (BJD)

2,458,337.2807

Long. of periastron (ω)

39.00°

Angular separation (arcsec)

2.21000

Eq. Temperature

643K

(370 °C)

Insolation (S⊕)

29.95

Earth = 1.00

Earth Similarity (ESI)

0.289

0 = alien, 1 = Earth-identical

Inside the inner HZ boundary (too hot for liquid water) — the surface is too hot to retain surface water.

Detection Signatures

Transit photometry

A transit dip has been observed from at least one telescope.

Radial velocity

Stellar wobble has been measured spectroscopically.

Transit timing variations

Gravitational interactions from neighbours have been detected.

Discovery Paper

Primary reference

Dransfield et al. 2022

Instrument

TESS CCD Array

Publication

2022-05

Observation locale

Space

Discovery cohort

Planets confirmed in 2022 at Transiting Exoplanet Survey Satellite (TESS) (12 shown).

TOI-1452 b · Super-Earth TOI-712 d · Sub-Neptune TOI-1468 c · Sub-Neptune TOI-2136 b · Sub-Neptune LTT 1445 A c · Rocky Terrestrial TOI-712 c · Sub-Neptune LP 890-9 b · Super-Earth TOI-2081 b · Sub-Neptune GJ 3929 b · Rocky Terrestrial HD 260655 c · Super-Earth HD 73583 c · Sub-Neptune TOI-1759 b · Sub-Neptune

Host System: HD 28109

Spectral Class

F-type yellow-white

Effective Temperature

6,189 K — hotter than the Sun (5,778 K)

Estimated Age

3.20 Gyr — younger than the Sun (4.6 Gyr)

Stellar Radius

1.425 R☉

Stellar Mass

1.227 M☉

Metallicity [Fe/H]

0.10

Extended Stellar Properties

Surface gravity (log g)

4.250 dex

Stellar density

0.621 g/cm³

Rotational v·sin i

8.00 km/s

Activity index (log R'HK)

-4.991

Metallicity ratio

[Fe/H]

Distance

139.61 parsec

Light-years 455.35 ly

V-band magnitude

9.42 mag

Voyager-speed travel 8,030,091 yr

Multi-band Host Photometry — 11 bands

Astrometric Data

Parallax

7.134 mas

Total Proper Motion

24.360 mas/yr

PM Right Ascension

22.03 mas/yr

PM Declination

-10.40 mas/yr

Galactic Cartesian (pc)

x = 0.156 · y = 0.339 · z = -0.928

Equatorial (J2000)

RA 65.23831° · Dec -68.10269°

Galactic ℓ, b

280.680° · -38.734°

Ecliptic λ, β

339.507° · -80.401°

HTM-20 index

574516844