Key parameters at a glance

A radius of 14.35 Earth radii
A mass of 331.80 Earth masses
Surface gravity around 1.61 g
An orbital period of 4.642 days
Semi-major axis 0.0575 AU
Equilibrium temperature 1,428 K (1155 °C)
Distance from Earth 1,321.71 light-years
Earth Similarity Index 0.088
Travel time at Voyager 1 speed 23,308,320 years

HAT-P-42 b Planet Profile

Physical Specs

Radius

14.35 R⊕

Radius (Jupiter)

1.280 R♃

Mass

331.80 M⊕

Mass (Jupiter)

1.044 M♃

Density

0.61 g/cm³

Surface Gravity

1.61 g (Earth)

Classification

Planet Type

Gas Giant

ESI Score 0.088

HZ Position Inner

Controversial No

Discovery

Year 2012

Method Transit

Facility HATNet

Telescope Canon 200mm f/1.8L

Size rank in cohort

Rank by radius

#297of 1771

top 16.7%

This planet

14.35R⊕

Gas Giant median

13.52R⊕

Nearest-size peers

TOI-6130 b 14.35 R⊕ TOI-2152 A b 14.36 R⊕ TOI-4794 b 14.36 R⊕

Metric	Earth	HAT-P-42 b	Jupiter
Radius (R⊕)	1.00	14.35	11.21
Mass (M⊕)	1.00	331.80	317.83
Density (g/cm³)	5.51	0.61	1.33
Surface Gravity (g)	1.00	1.61	2.53
Insolation (S⊕)	1.00	684.10	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	331.801 M⊕	Direct mass measurement (not derived).

Star Catalogue Identifiers

TIC

TIC 270468559

Gaia DR2

Gaia DR2 583455604761166848

Gaia DR3

Gaia DR3 583455604761166848

System

HAT-P-42

Percentile among Gas Giant cohort

Radius 14.348 R⊕ · percentile 83 / cohort 1771

Mass 331.801 M⊕ · percentile 36 / cohort 1747

Orbital period 4.64 d · percentile 35 / cohort 1533

Distance 405.24 pc · percentile 70 / cohort 1759

ESI 0.088 · percentile 22 / cohort 1771

Orbit & Habitability

Orbital Dynamics

Period

4.642 days

Semi-major axis

0.0575 AU

Eccentricity

0.000

Inclination

85.90 °

Year Length

A year here lasts approximately 4.64 Earth days (1.3% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0575 AU.

Transit Fingerprint

Depth

0.753 %

Duration

4.034 h

Impact parameter b

0.577

Rp / R★

0.086000

Transit midpoint (BJD)

2,455,952.5260

Photometric dip

Transit produces a flux drop of 7,525 ppm lasting ≈ 4.03 h.

Extended Orbital Architecture

Planet / star radius ratio

0.086000

Semi-major axis / stellar radius

8.080

Impact parameter (b)

0.577

RV semi-amplitude (K)

113.500 m/s

Transit mid-time (BJD)

2,455,952.5260

Angular separation (arcsec)

0.14200

Eq. Temperature

1,428K

(1155 °C)

Insolation (S⊕)

684.10

Earth = 1.00

Earth Similarity (ESI)

0.088

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

Boisse et al. 2013

Instrument

2K CCD Sensor

Publication

2013-10

Observation locale

Ground

Discovery cohort

Planets confirmed in 2012 at HATNet (5 shown).

HAT-P-38 b · Neptune-like HAT-P-43 b · Gas Giant HAT-P-39 b · Gas Giant HAT-P-40 b · Gas Giant HAT-P-41 b · Gas Giant

Host System: HAT-P-42

Spectral Class

G-type yellow (Sun-like)

Effective Temperature

5,743 K — cooler than the Sun (5,778 K)

Estimated Age

5.20 Gyr — older than the Sun (4.6 Gyr)

Stellar Radius

1.530 R☉

Stellar Mass

1.178 M☉

Metallicity [Fe/H]

0.27

Extended Stellar Properties

Surface gravity (log g)

4.140 dex

Stellar density

0.528 g/cm³

Systemic radial velocity

20.26 km/s

Rotational v·sin i

3.50 km/s

Metallicity ratio

[Fe/H]

Distance

405.24 parsec

Light-years 1,321.71 ly

V-band magnitude

12.13 mag

Voyager-speed travel 23,308,320 yr

Multi-band Host Photometry — 16 bands

Astrometric Data

Parallax

2.440 mas

Total Proper Motion

33.516 mas/yr

PM Right Ascension

-2.91 mas/yr

PM Declination

-33.39 mas/yr

Galactic Cartesian (pc)

x = -0.707 · y = 0.699 · z = 0.106

Equatorial (J2000)

RA 135.34436° · Dec 6.09708°

Galactic ℓ, b

223.004° · 31.582°

Ecliptic λ, β

135.979° · -10.401°

HTM-20 index

1352622032