Key parameters at a glance

A radius of 3.83 Earth radii
A mass of 8.30 Earth masses
Surface gravity around 0.57 g
An orbital period of 20.773 days
Semi-major axis 0.1450 AU
Equilibrium temperature 641 K (368 °C)
Distance from Earth 220.31 light-years
Earth Similarity Index 0.303
Travel time at Voyager 1 speed 3,885,188 years

1 sibling around HIP 9618

HIP 9618 b shares its host star with 1 other confirmed planet. Side-by-side measurements below.

Planet	Type	Radius (R⊕)	Mass (M⊕)	Period (d)	Eq. T (K)	Year
HIP 9618 b this	Sub-Neptune	3.83	8.30	20.773	641	2023
HIP 9618 c	Sub-Neptune	3.43	7.00	52.564	470	2023

HIP 9618 b Planet Profile

Physical Specs

Radius

3.83 R⊕

Radius (Jupiter)

0.342 R♃

Mass

8.30 M⊕

Mass (Jupiter)

0.026 M♃

Density

0.81 g/cm³

Surface Gravity

0.57 g (Earth)

Classification

Planet Type

Sub-Neptune

ESI Score 0.303

HZ Position Inner

Controversial No

Discovery

Year 2023

Method Transit

Facility Transiting Exoplanet Survey Satellite (TESS)

Telescope 0.1 m TESS Telescope

Size rank in cohort

Rank by radius

#53of 1978

top 2.6%

This planet

3.83R⊕

Sub-Neptune median

2.71R⊕

Nearest-size peers

TOI-1422 b 3.83 R⊕ HD 20781 e 3.83 R⊕ Kepler-232 c 3.83 R⊕

Metric	Earth	HIP 9618 b	Jupiter
Radius (R⊕)	1.00	3.83	11.21
Mass (M⊕)	1.00	8.30	317.83
Density (g/cm³)	5.51	0.81	1.33
Surface Gravity (g)	1.00	0.57	2.53
Insolation (S⊕)	1.00	40.30	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	8.300 M⊕	Direct mass measurement (not derived).

Star Catalogue Identifiers

HD 12572

HIP

HIP 9618

TIC

TIC 306263608

Gaia DR2

Gaia DR2 94468978202180352

Gaia DR3

Gaia DR3 94468978202180352

System

HIP 9618

Percentile among Sub-Neptune cohort

Radius 3.828 R⊕ · percentile 97 / cohort 1978

Mass 8.300 M⊕ · percentile 57 / cohort 1978

Orbital period 20.77 d · percentile 64 / cohort 1946

Distance 67.55 pc · percentile 15 / cohort 1975

ESI 0.303 · percentile 28 / cohort 1978

Orbit & Habitability

Orbital Dynamics

Period

20.773 days

Semi-major axis

0.1450 AU

Eccentricity

0.000

Inclination

— °

Year Length

A year here lasts approximately 20.77 Earth days (5.7% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.1450 AU.

Transit Fingerprint

Depth

0.142 %

Duration

4.943 h

Impact parameter b

0.248

Rp / R★

0.036589

Transit midpoint (BJD)

2,458,767.4228

Photometric dip

Transit produces a flux drop of 1,415 ppm lasting ≈ 4.94 h.

Extended Orbital Architecture

Planet / star radius ratio

0.036589

Semi-major axis / stellar radius

32.900

Impact parameter (b)

0.248

RV semi-amplitude (K)

2.060 m/s

Transit mid-time (BJD)

2,458,767.4228

Long. of periastron (ω)

90.00°

Angular separation (arcsec)

2.15000

Eq. Temperature

641K

(368 °C)

Insolation (S⊕)

40.30

Earth = 1.00

Earth Similarity (ESI)

0.303

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.

Discovery Paper

Primary reference

Osborn et al. 2023

Instrument

TESS CCD Array

Publication

2023-08

Observation locale

Space

Discovery cohort

Planets confirmed in 2023 at Transiting Exoplanet Survey Satellite (TESS) (12 shown).

TOI-700 e · Rocky Terrestrial TOI-2095 c · Super-Earth TOI-715 b · Super-Earth TOI-2095 b · Super-Earth TOI-2096 c · Super-Earth TOI-1680 b · Super-Earth TOI-2096 b · Rocky Terrestrial TOI-904 c · Sub-Neptune TOI-1470 c · Sub-Neptune TOI-198 b · Super-Earth TOI-244 b · Super-Earth TOI-4184 b · Sub-Neptune

Host System: HIP 9618

Spectral Class

G-type yellow (Sun-like)

Effective Temperature

5,649 K — cooler than the Sun (5,778 K)

Estimated Age

5.60 Gyr — older than the Sun (4.6 Gyr)

Stellar Radius

0.959 R☉

Stellar Mass

0.942 M☉

Metallicity [Fe/H]

-0.02

Extended Stellar Properties

Surface gravity (log g)

4.445 dex

Stellar density

1.490 g/cm³

Activity index (log R'HK)

-4.990

Metallicity ratio

[Fe/H]

Distance

67.55 parsec

Light-years 220.31 ly

V-band magnitude

9.20 mag

Voyager-speed travel 3,885,188 yr

Multi-band Host Photometry — 11 bands

Astrometric Data

Parallax

14.776 mas

Total Proper Motion

191.883 mas/yr

PM Right Ascension

158.82 mas/yr

PM Declination

107.68 mas/yr

Galactic Cartesian (pc)

x = 0.800 · y = 0.479 · z = 0.363

Equatorial (J2000)

RA 30.90501° · Dec 21.28133°

Galactic ℓ, b

144.587° · -38.536°

Ecliptic λ, β

36.118° · 8.200°

HTM-20 index

1752874521