WASP-78

WASP-78, is a single F-type main-sequence star about 2350 light-years away. It is likely to be younger than the Sun at 3.4^+1.5
_−0.8 billion years.^[5] WASP-78 is depleted in heavy elements, having a 45% concentration of iron compared to the Sun.

WASP-78

Observation data Epoch J2000      Equinox J2000
Constellation	Eridanus
Right ascension	04h 15m 01.5043s[1]
Declination	−22° 06′ 59.103″[1]
Apparent magnitude (V)	12.0[2]
Characteristics
Evolutionary stage	main-sequence star[citation needed]
Spectral type	F8[2]
Astrometry
Radial velocity (Rv)	1.26[3] km/s
Proper motion (μ)	RA: −0.367(11) mas/yr[1] Dec.: 6.395(13) mas/yr[1]
Parallax (π)	1.3851±0.0136 mas[1]
Distance	2,350 ± 20 ly (722 ± 7 pc)
Details
Mass	1.33±0.09[2] M☉
Radius	2.20±0.12[2] R☉
Luminosity	5.8±0.2[4] L☉
Surface gravity (log g)	3.88±0.04[2] cgs
Temperature	6100±150[2] K
Metallicity [Fe/H]	-0.35±0.14[2] dex
Rotation	0.4±0.4[2]
Rotational velocity (v sin i)	6.63±0.16[5] km/s
Age	3.4+1.5 −0.8[5] Gyr
Other designations
Gaia DR2 5089851638095503616, TYC 5889-271-1, GSC 05889-00271, 2MASS J04150149-2206591[3]
Database references
SIMBAD	data

Planetary system

In 2012 a transiting hot Jupiter planet b was detected on a circular orbit. The planetary equilibrium temperature is 2350±80 K,^[2] while the nightside temperature measured in 2019 is 2200±41 K.^[6] The dayside planetary temperature measured in 2020 is 2560±130 K.^[7]

A survey in 2016 measured a Rossiter-McLaughlin effect and found the planetary orbit is well aligned with the equatorial plane of the star, misalignment equal to −6.4±5.9°^[5] The planet cannot have formed in its current orbit and has likely undergone in the past a migration from the initial highly eccentric orbit.^[8]

The WASP-78 planetary system^[2]

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
b	0.89±0.08 MJ	0.0362±0.0008	2.17517632±0.0000047	0	83.2+2.3 −1.6°	1.70±0.11 RJ