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Exoplanet List of exoplanets
Exoplanet Comparison HAT-P-4 b.png
Size comparison of HAT-P-4b with Jupiter.
Parent star
Star HAT-P-4
Constellation Boötes
Right ascension (α) 15h 19m 58s
Declination (δ) +36° 13′ 47″
Distance 1010 ± 100 ly
(310 ± 30 pc)
Spectral type F
Orbital elements
Semi-major axis (a) 0.0446 ± 0.0012 AU
Eccentricity (e) 0
Orbital period (P) 3.056536 ± 0.000057 d
Orbital speed (υ) 158.55 km/s
Inclination (i) 89.9 +0.1
Argument of
(ω) 12.33°
Time of periastron (T0) 2,454,245.8154 JD
Semi-amplitude (K) 76.93 m/s
Physical characteristics
Mass (m) 0.68 ± 0.04 MJ
(216 ± 13 M)
Radius (r) 1.27 ± 0.05 RJ
(14.2 R)
Density (ρ) 410 ± 60 kg m−3
Surface gravity (g) 10.5 m/s² (1.07 g)
Discovery information
Discovery date Oct 2, 2007
Discoverer(s) Kovacs et al.
Discovery method transit
Discovery site Mass.,  USA
Discovery status Published
Database references
Extrasolar Planets
Exoplanet Archive data
Open Exoplanet Catalogue data

HAT-P-4b is an extrasolar planet orbiting the star HAT-P-4 over 1000 light years away in Boötes constellation. It was discovered by transit on October 2, 2007, which looks for slight dimming of stars caused by planets that passed in front of them. It is the fourth planet discovered by the HATNet Project.[1]

It is a hot Jupiter with 68% the mass and 127% the radius of Jupiter, and 41% the density of water (31% of Jupiter). Since the inclination is known by transit observation, the true mass is known.


  1. ^ Kovács, G.; et al. (2007). "HAT-P-4b: A Metal-rich Low-Density Transiting Hot Jupiter". The Astrophysical Journal Letters. 670 (1): L41–L44. arXiv:0710.0602Freely accessible. Bibcode:2007ApJ...670L..41K. doi:10.1086/524058. 

External links[edit]

Media related to HAT-P-4b at Wikimedia Commons

Coordinates: Sky map 15h 19m 58s, +36° 13′ 47″