Key parameters at a glance

A radius of 21.63 Earth radii
A mass of 352.79 Earth masses
Surface gravity around 0.75 g
An orbital period of 2.175 days
Semi-major axis 0.0349 AU
Equilibrium temperature 2,470 K (2197 °C)
Distance from Earth 2,460.06 light-years
Earth Similarity Index 0.030
Travel time at Voyager 1 speed 43,383,116 years

WASP-78 b Planet Profile

Physical Specs

Radius

21.63 R⊕

Radius (Jupiter)

1.930 R♃

Mass

352.79 M⊕

Mass (Jupiter)

1.110 M♃

Density

0.13 g/cm³

Surface Gravity

0.75 g (Earth)

Classification

Planet Type

Gas Giant

ESI Score 0.030

HZ Position Inner

Controversial No

Discovery

Year 2012

Method Transit

Facility SuperWASP

Telescope Canon 200mm f/1.8L

Size rank in cohort

Rank by radius

#18of 1771

top 1.0%

This planet

21.63R⊕

Gas Giant median

13.52R⊕

Nearest-size peers

BD-14 3065 b 21.59 R⊕ KELT-19 A b 21.41 R⊕ PDS 70 b 21.97 R⊕

Metric	Earth	WASP-78 b	Jupiter
Radius (R⊕)	1.00	21.63	11.21
Mass (M⊕)	1.00	352.79	317.83
Density (g/cm³)	5.51	0.13	1.33
Surface Gravity (g)	1.00	0.75	2.53
Insolation (S⊕)	1.00	4,812.62	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	352.791 M⊕	Direct mass measurement (not derived).

Star Catalogue Identifiers

TIC

TIC 139528693

Gaia DR2

Gaia DR2 5089851638095503616

Gaia DR3

Gaia DR3 5089851638095503616

System

WASP-78

Percentile among Gas Giant cohort

Radius 21.633 R⊕ · percentile 99 / cohort 1771

Mass 352.791 M⊕ · percentile 38 / cohort 1747

Orbital period 2.18 d · percentile 8 / cohort 1533

Distance 754.26 pc · percentile 82 / cohort 1759

ESI 0.030 · percentile 1 / cohort 1771

Orbit & Habitability

Orbital Dynamics

Period

2.175 days

Semi-major axis

0.0349 AU

Eccentricity

0.000

Inclination

83.20 °

Year Length

A year here lasts approximately 2.18 Earth days (0.6% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0349 AU.

Transit Fingerprint

Depth

0.650 %

Duration

4.968 h

Impact parameter b

0.510

Rp / R★

0.085200

Transit midpoint (BJD)

2,457,966.1863

Photometric dip

Transit produces a flux drop of 6,500 ppm lasting ≈ 4.97 h.

Extended Orbital Architecture

Planet / star radius ratio

0.085200

Semi-major axis / stellar radius

3.540

Impact parameter (b)

0.510

RV semi-amplitude (K)

113.800 m/s

Transit mid-time (BJD)

2,457,966.1863

Sky-projected obliquity (λ)

-6.40°

Angular separation (arcsec)

0.04620

Eq. Temperature

2,470K

(2197 °C)

Insolation (S⊕)

4,812.62

Earth = 1.00

Earth Similarity (ESI)

0.030

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

Smalley et al. 2012

Instrument

iKon-L CCD Camera

Publication

2012-11

Observation locale

Ground

Discovery cohort

Planets confirmed in 2012 at SuperWASP (12 shown).

WASP-59 b · Neptune-like WASP-80 b · Gas Giant WASP-42 b · Gas Giant WASP-67 b · Gas Giant WASP-56 b · Gas Giant WASP-47 b · Gas Giant WASP-41 b · Gas Giant WASP-57 b · Gas Giant WASP-58 b · Gas Giant WASP-52 b · Gas Giant WASP-55 b · Gas Giant WASP-61 b · Gas Giant

Host System: WASP-78

Spectral Class

F-type yellow-white

Effective Temperature

6,100 K — hotter than the Sun (5,778 K)

Estimated Age

2.80 Gyr — younger than the Sun (4.6 Gyr)

Stellar Radius

2.460 R☉

Stellar Mass

1.870 M☉

Metallicity [Fe/H]

-0.35

Extended Stellar Properties

Surface gravity (log g)

4.100 dex

Stellar density

0.180 g/cm³

Systemic radial velocity

0.48 km/s

Rotational v·sin i

7.10 km/s

Metallicity ratio

[Fe/H]

Distance

754.26 parsec

Light-years 2,460.06 ly

V-band magnitude

11.97 mag

Voyager-speed travel 43,383,116 yr

Multi-band Host Photometry — 11 bands

Astrometric Data

Parallax

1.297 mas

Total Proper Motion

6.441 mas/yr

PM Right Ascension

-0.46 mas/yr

PM Declination

6.42 mas/yr

Galactic Cartesian (pc)

x = 0.410 · y = 0.831 · z = -0.376

Equatorial (J2000)

RA 63.75627° · Dec -22.11639°

Galactic ℓ, b

218.385° · -43.765°

Ecliptic λ, β

56.225° · -42.528°

HTM-20 index

431766473