Key parameters at a glance
- A radius of 15.69 Earth radii
- A mass of 406.82 Earth masses
- Surface gravity around 1.65 g
- An orbital period of 3.076 days
- Semi-major axis 0.0450 AU
- Equilibrium temperature 1,713 K (1440 °C)
- Distance from Earth 689.99 light-years
- Earth Similarity Index 0.072
- Travel time at Voyager 1 speed 12,168,022 years
HAT-P-8 b Planet Profile
Physical Specs
Classification
Planet Type
Gas Giant
Discovery
Size rank in cohort
Rank by radius
#180of 1771
top 10.1%
This planet
15.69R⊕
Gas Giant median
13.52R⊕
Nearest-size peers
| Metric | Earth | HAT-P-8 b | Jupiter |
|---|---|---|---|
| Radius (R⊕) | 1.00 | 15.69 | 11.21 |
| Mass (M⊕) | 1.00 | 406.82 | 317.83 |
| Density (g/cm³) | 5.51 | 0.69 | 1.33 |
| Surface Gravity (g) | 1.00 | 1.65 | 2.53 |
| Insolation (S⊕) | 1.00 | 1,519.96 | 0.037 |
Alternative Mass Estimates
| Method | Value | Interpretation |
|---|---|---|
| Best measured mass | 406.822 M⊕ | Direct mass measurement (not derived). |
Star Catalogue Identifiers
TIC
TIC 188876052
Gaia DR2
Gaia DR2 1891507552824189568
Gaia DR3
Gaia DR3 1891507552826485632
System
HAT-P-8
Percentile among Gas Giant cohort
Orbit & Habitability
Orbital Dynamics
Year Length
A year here lasts approximately 3.08 Earth days (0.8% of a terrestrial year) on a nearly circular orbit at a mean orbital distance of 0.0450 AU.
Transit Fingerprint
Depth
0.830 %
Duration
3.902 h
Impact parameter b
0.320
Rp / R★
0.092100
Transit midpoint (BJD)
2,456,052.7560
Photometric dip
Transit produces a flux drop of 8,300 ppm lasting ≈ 3.90 h.
Extended Orbital Architecture
Planet / star radius ratio
0.092100
Semi-major axis / stellar radius
6.130
Impact parameter (b)
0.320
RV semi-amplitude (K)
153.100 m/s
Transit mid-time (BJD)
2,456,052.7560
Long. of periastron (ω)
116.00°
Sky-projected obliquity (λ)
-17.00°
Angular separation (arcsec)
0.21300
Eq. Temperature
1,713K
(1440 °C)
Insolation (S⊕)
1,519.96
Earth = 1.00
Earth Similarity (ESI)
0.072
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
Latham et al. 2009Instrument
2K CCD Sensor
Publication
2009-10
Observation locale
Ground
Discovery cohort
Planets confirmed in 2008 at HATNet (3 shown).
Host System: HAT-P-8
Spectral Class
F-type yellow-white
Effective Temperature
6,200 K — hotter than the Sun (5,778 K)
Estimated Age
3.40 Gyr — younger than the Sun (4.6 Gyr)
Stellar Radius
1.570 R☉
Stellar Mass
1.270 M☉
Metallicity [Fe/H]
0.01
Extended Stellar Properties
Surface gravity (log g)
4.150 dex
Stellar density
0.460 g/cm³
Systemic radial velocity
-22.38 km/s
Rotational v·sin i
11.50 km/s
Metallicity ratio
[Fe/H]
Multi-band Host Photometry — 11 bands
Astrometric Data
Parallax
4.698 mas
Total Proper Motion
76.247 mas/yr
PM Right Ascension
74.75 mas/yr
PM Declination
15.05 mas/yr
Galactic Cartesian (pc)
x = 0.779 · y = -0.238 · z = 0.580
Equatorial (J2000)
RA 343.04149° · Dec 35.44718°
Galactic ℓ, b
97.145° · -21.383°
Ecliptic λ, β
0.929° · 38.801°
HTM-20 index
126243890
Observation Record
Photometric series
8
RV measurements
1
Emission spectra
3
Archive notes
3
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