4 Ursae Majoris b

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**4 Ursae Majoris b**
Parent star
Extrasolar planet		List of extrasolar planets
Star		4 Ursae Majoris
Constellation		Ursa Major
Right ascension	(α)	08^h 40^m 12.8^s
Declination	(δ)	+64° 19′ 40″
Distance		252 ly (77 pc)
Spectral type		K1+IIIb
Orbital elements
Semimajor axis	(a)	0.87 ± 0.04 AU
Eccentricity	(e)	0.432 ± 0.024
Orbital period	(P)	269.3 ± 1.96 d
Angular distance	(θ)	13.945 mas
Longitude of periastron	(ω)	23.81 ± 4.42°
Time of periastron	(T₀)	2,452,987.3936 ± 4.31 JD
Semi-amplitude	(K)	215.6 ± 7.1 m/s
Physical characteristics
Mass	(m)	>7.1 ± 1.6 M_J
Radius	(r)	>0.95 R_J
Discovery information
Discovery date		28 March 2007
Discoverer(s)		Doellinger et al.
Detection method		Doppler Spectroscopy
Discovery status		Published
Other designations
Pi² Ursae Majoris b, HD 73108 b, HIP 42527 b, HR 3403 b, SAO 14616 b

4 Ursae Majoris b, also known as Pi² Ursae Majoris b, is an extrasolar planet orbiting the star 4 Ursae Majoris, approximately 252 light-years away in the constellation of Ursa Major. The mass is calculated to be over 7 times more than Jupiter, classifying as mid-superjovian (Ib). It eccentrically orbits the star a little bit closer than Earth to the Sun, but it takes only three-fourths of a year in period. This makes the orbital velocity 12% faster than the Earth.

It has a fast semi-amplitude of 215.6 m/s because the planet is a mid-superjovian that orbits slightly closer than Earth to the star. The radius is probably slightly smaller than Jupiter and has a very strong gravitational pull.

[edit] See also

[edit] References

M.P. Doellinger, A. P. Hatzes, L. Pasquini, E. W. Guenther, M. Hartmann, L. Girardi, M. Esposito (2007). "Discovery of a planet around the K giant star 4 UMa".