HAT-P-4b

HAT-P-4b

Extrasolar planet		List of extrasolar planets
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
Semimajor 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 −2.2°
Argument of periastron	(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.
Detection method		transit
Discovery site		Mass., USA
Discovery status		Published
Database references
Extrasolar Planets Encyclopaedia		data
SIMBAD		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.

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.

References

• Kovács et al.; Bakos, G. Á.; Torres, G.; Sozzetti, A.; Latham, D. W.; Noyes, R. W.; Butler, R. P.; Marcy, G. W. et al (2007). "HAT-P-4b: A Metal-rich Low-Density Transiting Hot Jupiter". The Astrophysical Journal Letters 670 (1): L41–L44. Bibcode 2007ApJ...670L..41K. doi:10.1086/524058. http://www.iop.org/EJ/article/1538-4357/670/1/L41/22113.html. 

External links

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