Key parameters at a glance

A radius of 9.79 Earth radii
A mass of 43.86 Earth masses
Surface gravity around 0.46 g
An orbital period of 3.584 days
Semi-major axis 0.0467 AU
Equilibrium temperature 1,324 K (1051 °C)
Distance from Earth 2,591.76 light-years
Earth Similarity Index 0.091
Travel time at Voyager 1 speed 45,705,619 years

HATS-8 b Planet Profile

Physical Specs

Radius

9.79 R⊕

Radius (Jupiter)

0.873 R♃

Mass

43.86 M⊕

Mass (Jupiter)

0.138 M♃

Density

0.26 g/cm³

Surface Gravity

0.46 g (Earth)

Classification

Planet Type

Neptune-like

ESI Score 0.091

HZ Position Inner

Controversial No

Discovery

Year 2015

Method Transit

Facility HATSouth

Telescope 0.18 m Takahashi Epsilon Astrograph

Size rank in cohort

Rank by radius

#18of 574

top 3.0%

This planet

9.79R⊕

Neptune-like median

6.39R⊕

Nearest-size peers

Kepler-56 c 9.80 R⊕ Kepler-1517 b 9.76 R⊕ Kepler-688 b 9.76 R⊕

Metric	Earth	HATS-8 b	Jupiter
Radius (R⊕)	1.00	9.79	11.21
Mass (M⊕)	1.00	43.86	317.83
Density (g/cm³)	5.51	0.26	1.33
Surface Gravity (g)	1.00	0.46	2.53
Insolation (S⊕)	1.00	510.82	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	43.861 M⊕	Direct mass measurement (not derived).

Star Catalogue Identifiers

TIC

TIC 96847781

Gaia DR2

Gaia DR2 6767008363999712512

Gaia DR3

Gaia DR3 6767008363999712512

System

HATS-8

Percentile among Neptune-like cohort

Radius 9.785 R⊕ · percentile 97 / cohort 574

Mass 43.861 M⊕ · percentile 66 / cohort 574

Orbital period 3.58 d · percentile 9 / cohort 524

Distance 794.64 pc · percentile 67 / cohort 572

ESI 0.091 · percentile 2 / cohort 574

Orbit & Habitability

Orbital Dynamics

Period

3.584 days

Semi-major axis

0.0467 AU

Eccentricity

0.376

Inclination

87.80 °

Year Length

A year here lasts approximately 3.58 Earth days (1.0% of a terrestrial year) on a highly eccentric trajectory at a mean orbital distance of 0.0467 AU.

Transit Fingerprint

Depth

0.773 %

Duration

3.031 h

Impact parameter b

0.360

Rp / R★

0.081400

Transit midpoint (BJD)

2,456,672.1102

Photometric dip

Transit produces a flux drop of 7,728 ppm lasting ≈ 3.03 h.

Extended Orbital Architecture

Planet / star radius ratio

0.081400

Semi-major axis / stellar radius

9.210

Impact parameter (b)

0.360

RV semi-amplitude (K)

17.700 m/s

Transit mid-time (BJD)

2,456,672.1102

Angular separation (arcsec)

0.05870

Eq. Temperature

1,324K

(1051 °C)

Insolation (S⊕)

510.82

Earth = 1.00

Earth Similarity (ESI)

0.091

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

Bayliss et al. 2015

Instrument

Apogee 4K CCD Sensor

Publication

2015-08

Observation locale

Ground

Discovery cohort

Planets confirmed in 2015 at HATSouth (6 shown).

HATS-6 b · Gas Giant HATS-7 b · Neptune-like HATS-14 b · Gas Giant HATS-10 b · Gas Giant HATS-13 b · Gas Giant HATS-9 b · Gas Giant

Host System: HATS-8

Spectral Class

G-type yellow (Sun-like)

Effective Temperature

5,679 K — cooler than the Sun (5,778 K)

Estimated Age

5.10 Gyr — older than the Sun (4.6 Gyr)

Stellar Radius

1.086 R☉

Stellar Mass

1.056 M☉

Metallicity [Fe/H]

0.21

Extended Stellar Properties

Surface gravity (log g)

4.386 dex

Stellar density

1.150 g/cm³

Systemic radial velocity

19.96 km/s

Rotational v·sin i

2.00 km/s

Metallicity ratio

[Fe/H]

Distance

794.64 parsec

Light-years 2,591.76 ly

V-band magnitude

14.51 mag

Voyager-speed travel 45,705,619 yr

Multi-band Host Photometry — 11 bands

Astrometric Data

Parallax

1.231 mas

Total Proper Motion

9.448 mas/yr

PM Right Ascension

-6.47 mas/yr

PM Declination

-6.89 mas/yr

Galactic Cartesian (pc)

x = 0.380 · y = -0.817 · z = -0.434

Equatorial (J2000)

RA 294.94169° · Dec -25.74837°

Galactic ℓ, b

14.084° · -21.462°

Ecliptic λ, β

292.383° · -4.227°

HTM-20 index

615165211