Key parameters at a glance

A radius of 17.82 Earth radii
A mass of 248.86 Earth masses
Surface gravity around 0.78 g
An orbital period of 2.972 days
Semi-major axis 0.0436 AU
Equilibrium temperature 1,896 K (1623 °C)
Distance from Earth 3,051.05 light-years
Earth Similarity Index 0.050
Travel time at Voyager 1 speed 53,805,191 years

HAT-P-66 b Planet Profile

Physical Specs

Radius

17.82 R⊕

Radius (Jupiter)

1.590 R♃

Mass

248.86 M⊕

Mass (Jupiter)

0.783 M♃

Density

0.24 g/cm³

Surface Gravity

0.78 g (Earth)

Classification

Planet Type

Gas Giant

ESI Score 0.050

HZ Position Inner

Controversial No

Discovery

Year 2016

Method Transit

Facility HATNet

Telescope Canon 200mm f/1.8L

Size rank in cohort

Rank by radius

#82of 1771

top 4.6%

This planet

17.82R⊕

Gas Giant median

13.52R⊕

Nearest-size peers

HAT-P-49 b 17.82 R⊕ WASP-33 b 17.86 R⊕ KELT-21 b 17.78 R⊕

Metric	Earth	HAT-P-66 b	Jupiter
Radius (R⊕)	1.00	17.82	11.21
Mass (M⊕)	1.00	248.86	317.83
Density (g/cm³)	5.51	0.24	1.33
Surface Gravity (g)	1.00	0.78	2.53
Insolation (S⊕)	1.00	1,939.51	0.037

Alternative Mass Estimates

Method	Value	Interpretation
Best measured mass	248.861 M⊕	Direct mass measurement (not derived).

Star Catalogue Identifiers

TIC

TIC 137881699

Gaia DR2

Gaia DR2 852608874351434752

Gaia DR3

Gaia DR3 852608874351434752

System

HAT-P-66

Percentile among Gas Giant cohort

Radius 17.822 R⊕ · percentile 95 / cohort 1771

Mass 248.861 M⊕ · percentile 27 / cohort 1747

Orbital period 2.97 d · percentile 15 / cohort 1533

Distance 935.46 pc · percentile 86 / cohort 1759

ESI 0.050 · percentile 4 / cohort 1771

Orbit & Habitability

Orbital Dynamics

Period

2.972 days

Semi-major axis

0.0436 AU

Eccentricity

0.090

Inclination

86.20 °

Year Length

A year here lasts approximately 2.97 Earth days (0.8% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0436 AU.

Transit Fingerprint

Depth

0.644 %

Duration

4.699 h

Impact parameter b

0.330

Rp / R★

0.087200

Transit midpoint (BJD)

2,457,258.7991

Photometric dip

Transit produces a flux drop of 6,440 ppm lasting ≈ 4.70 h.

Extended Orbital Architecture

Planet / star radius ratio

0.087200

Semi-major axis / stellar radius

5.010

Impact parameter (b)

0.330

RV semi-amplitude (K)

93.500 m/s

Transit mid-time (BJD)

2,457,258.7991

Angular separation (arcsec)

0.04660

Eq. Temperature

1,896K

(1623 °C)

Insolation (S⊕)

1,939.51

Earth = 1.00

Earth Similarity (ESI)

0.050

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

Hartman et al. 2016

Instrument

2K CCD Sensor

Publication

2016-12

Observation locale

Ground

Host System: HAT-P-66

Spectral Class

G-type yellow (Sun-like)

Effective Temperature

6,002 K — hotter than the Sun (5,778 K)

Estimated Age

4.66 Gyr — older than the Sun (4.6 Gyr)

Stellar Radius

1.881 R☉

Stellar Mass

1.255 M☉

Metallicity [Fe/H]

0.04

Extended Stellar Properties

Surface gravity (log g)

3.993 dex

Stellar density

0.269 g/cm³

Systemic radial velocity

1.94 km/s

Rotational v·sin i

7.57 km/s

Metallicity ratio

[Fe/H]

Distance

935.46 parsec

Light-years 3,051.05 ly

V-band magnitude

13.01 mag

Voyager-speed travel 53,805,191 yr

Multi-band Host Photometry — 17 bands

Astrometric Data

Parallax

1.040 mas

Total Proper Motion

17.908 mas/yr

PM Right Ascension

-9.38 mas/yr

PM Declination

-15.25 mas/yr

Galactic Cartesian (pc)

x = -0.513 · y = 0.289 · z = 0.809

Equatorial (J2000)

RA 150.57263° · Dec 53.95082°

Galactic ℓ, b

160.163° · 49.124°

Ecliptic λ, β

131.129° · 38.813°

HTM-20 index

-2021076836