Key parameters at a glance

A radius of 6.88 Earth radii
A mass of 23.52 Earth masses
Surface gravity around 0.50 g
An orbital period of 4.375 days
Semi-major axis 0.0504 AU
Equilibrium temperature 1,294 K (1021 °C)
Distance from Earth 1,120.43 light-years
Earth Similarity Index 0.111
Travel time at Voyager 1 speed 19,758,736 years

HATS-38 b Planet Profile

Physical Specs

Radius

6.88 R⊕

Radius (Jupiter)

0.614 R♃

Mass

23.52 M⊕

Mass (Jupiter)

0.074 M♃

Density

0.40 g/cm³

Surface Gravity

0.50 g (Earth)

Classification

Planet Type

Neptune-like

ESI Score 0.111

HZ Position Inner

Controversial No

Discovery

Year 2020

Method Transit

Facility HATSouth

Telescope 0.18 m Takahashi Epsilon Astrograph

Size rank in cohort

Rank by radius

#214of 574

top 37.1%

This planet

6.88R⊕

Neptune-like median

6.39R⊕

Nearest-size peers

HD 34445 f 6.88 R⊕ Kepler-799 b 6.88 R⊕ KIC 3558849 b 6.90 R⊕

Metric	Earth	HATS-38 b	Jupiter
Radius (R⊕)	1.00	6.88	11.21
Mass (M⊕)	1.00	23.52	317.83
Density (g/cm³)	5.51	0.40	1.33
Surface Gravity (g)	1.00	0.50	2.53
Insolation (S⊕)	1.00	464.70	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	23.519 M⊕	Direct mass measurement (not derived).

Star Catalogue Identifiers

TIC

TIC 168281028

Gaia DR2

Gaia DR2 5472386851683941376

Gaia DR3

Gaia DR3 5472386851683941376

System

HATS-38

Percentile among Neptune-like cohort

Radius 6.882 R⊕ · percentile 63 / cohort 574

Mass 23.519 M⊕ · percentile 39 / cohort 574

Orbital period 4.38 d · percentile 17 / cohort 524

Distance 343.53 pc · percentile 50 / cohort 572

ESI 0.111 · percentile 4 / cohort 574

Orbit & Habitability

Orbital Dynamics

Period

4.375 days

Semi-major axis

0.0504 AU

Eccentricity

0.000

Inclination

87.21 °

Year Length

A year here lasts approximately 4.38 Earth days (1.2% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0504 AU.

Transit Fingerprint

Depth

0.327 %

Duration

3.216 h

Impact parameter b

0.476

Rp / R★

0.057000

Transit midpoint (BJD)

2,457,725.1604

Photometric dip

Transit produces a flux drop of 3,271 ppm lasting ≈ 3.22 h.

Extended Orbital Architecture

Planet / star radius ratio

0.057000

Semi-major axis / stellar radius

9.810

Impact parameter (b)

0.476

RV semi-amplitude (K)

9.900 m/s

Transit mid-time (BJD)

2,457,725.1604

Angular separation (arcsec)

0.14700

Eq. Temperature

1,294K

(1021 °C)

Insolation (S⊕)

464.70

Earth = 1.00

Earth Similarity (ESI)

0.111

0 = alien, 1 = Earth-identical

Inside the inner HZ boundary (too hot for liquid water) — the dayside is scorched.

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

Jord Aacute N et al. 2020

Instrument

Apogee 4K CCD Sensor

Publication

2020-11

Observation locale

Ground

Discovery cohort

Planets confirmed in 2020 at HATSouth (6 shown).

HATS-71 b · Gas Giant HATS-49 b · Neptune-like HATS-72 b · Neptune-like HATS-48 A b · Neptune-like HATS-47 b · Gas Giant HATS-37 A b · Neptune-like

Host System: HATS-38

Spectral Class

G-type yellow (Sun-like)

Effective Temperature

5,732 K — cooler than the Sun (5,778 K)

Estimated Age

11.89 Gyr — older than the Sun (4.6 Gyr)

Stellar Radius

1.105 R☉

Stellar Mass

0.890 M☉

Metallicity [Fe/H]

-0.10

Extended Stellar Properties

Surface gravity (log g)

4.301 dex

Stellar density

1.025 g/cm³

Systemic radial velocity

4.14 km/s

Rotational v·sin i

3.10 km/s

Metallicity ratio

[Fe/H]

Distance

343.53 parsec

Light-years 1,120.43 ly

V-band magnitude

11.97 mag

Voyager-speed travel 19,758,736 yr

Multi-band Host Photometry — 14 bands

Astrometric Data

Parallax

2.883 mas

Total Proper Motion

23.021 mas/yr

PM Right Ascension

-21.75 mas/yr

PM Declination

-7.54 mas/yr

Galactic Cartesian (pc)

x = -0.815 · y = 0.393 · z = -0.427

Equatorial (J2000)

RA 154.27106° · Dec -25.27630°

Galactic ℓ, b

264.165° · 25.744°

Ecliptic λ, β

166.846° · -33.223°

HTM-20 index

196938743