Key parameters at a glance

A radius of 16.02 Earth radii
A mass of 231.70 Earth masses
Surface gravity around 0.90 g
An orbital period of 2.716 days
Semi-major axis 0.0391 AU
Equilibrium temperature 1,623 K (1350 °C)
Distance from Earth 1,299.75 light-years
Earth Similarity Index 0.066
Travel time at Voyager 1 speed 22,921,054 years

WASP-81 b Planet Profile

Physical Specs

Radius

16.02 R⊕

Radius (Jupiter)

1.429 R♃

Mass

231.70 M⊕

Mass (Jupiter)

0.729 M♃

Density

0.33 g/cm³

Surface Gravity

0.90 g (Earth)

Classification

Planet Type

Gas Giant

ESI Score 0.066

HZ Position Inner

Controversial No

Discovery

Year 2017

Method Transit

Facility Multiple Facilities

Telescope Multiple Telescopes

Size rank in cohort

Rank by radius

#161of 1771

top 9.0%

This planet

16.02R⊕

Gas Giant median

13.52R⊕

Nearest-size peers

WASP-101 b 16.03 R⊕ HATS-34 b 16.03 R⊕ WASP-58 b 16.03 R⊕

Metric	Earth	WASP-81 b	Jupiter
Radius (R⊕)	1.00	16.02	11.21
Mass (M⊕)	1.00	231.70	317.83
Density (g/cm³)	5.51	0.33	1.33
Surface Gravity (g)	1.00	0.90	2.53
Insolation (S⊕)	1.00	1,034.09	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	231.698 M⊕	Direct mass measurement (not derived).

Star Catalogue Identifiers

TIC

TIC 399402994

Gaia DR2

Gaia DR2 4244243354278985472

Gaia DR3

Gaia DR3 4244243354278985472

System

WASP-81

Percentile among Gas Giant cohort

Radius 16.018 R⊕ · percentile 91 / cohort 1771

Mass 231.698 M⊕ · percentile 24 / cohort 1747

Orbital period 2.72 d · percentile 12 / cohort 1533

Distance 398.51 pc · percentile 69 / cohort 1759

ESI 0.066 · percentile 11 / cohort 1771

Orbit & Habitability

Orbital Dynamics

Period

2.716 days

Semi-major axis

0.0391 AU

Eccentricity

0.066

Inclination

88.69 °

Year Length

A year here lasts approximately 2.72 Earth days (0.7% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0391 AU.

Transit Fingerprint

Depth

1.453 %

Duration

3.530 h

Rp / R★

0.112000

Transit midpoint (BJD)

2,456,195.5746

Photometric dip

Transit produces a flux drop of 14,527 ppm lasting ≈ 3.53 h.

Extended Orbital Architecture

Planet / star radius ratio

0.112000

Semi-major axis / stellar radius

6.560

RV semi-amplitude (K)

100.800 m/s

Transit mid-time (BJD)

2,456,195.5746

Angular separation (arcsec)

0.09810

Eq. Temperature

1,623K

(1350 °C)

Insolation (S⊕)

1,034.09

Earth = 1.00

Earth Similarity (ESI)

0.066

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

Triaud et al. 2017

Instrument

Multiple Instruments

Publication

2017-05

Observation locale

Ground

Discovery cohort

Planets confirmed in 2017 at Multiple Facilities (4 shown).

PSR B0329+54 b · Rocky Terrestrial TAP 26 b · Gas Giant WASP-53 b · Gas Giant WASP-53 c · Unclassified

Host System: WASP-81

Spectral Class

G-type yellow (Sun-like)

Effective Temperature

5,870 K — hotter than the Sun (5,778 K)

Estimated Age

—

Stellar Radius

1.283 R☉

Stellar Mass

1.080 M☉

Metallicity [Fe/H]

-0.36

Extended Stellar Properties

Surface gravity (log g)

4.258 dex

Stellar density

0.723 g/cm³

Systemic radial velocity

-60.29 km/s

Metallicity ratio

[Fe/H]

Distance

398.51 parsec

Light-years 1,299.75 ly

V-band magnitude

12.47 mag

Voyager-speed travel 22,921,054 yr

Multi-band Host Photometry — 11 bands

Astrometric Data

Parallax

2.482 mas

Total Proper Motion

31.214 mas/yr

PM Right Ascension

27.20 mas/yr

PM Declination

-15.32 mas/yr

Galactic Cartesian (pc)

x = 0.561 · y = -0.826 · z = 0.057

Equatorial (J2000)

RA 304.20799° · Dec 3.29395°

Galactic ℓ, b

46.060° · -17.293°

Ecliptic λ, β

307.376° · 22.404°

HTM-20 index

1621023262