Gamma1 Leonis b is an exoplanet orbiting the primary component of the binary star system Gamma Leonis, also known by its traditional name Algieba. It is a gas giant located approximately 130 light-years from Earth in the constellation Leo. The "b" designation indicates that it was the first planet discovered in this star system.
Discovery The planet Gamma1 Leonis b was discovered in 2009 using the radial velocity method, which detects the subtle wobble in a star caused by the gravitational pull of an orbiting planet. The discovery was announced by a team led by B. Sato, confirming the presence of a massive object in orbit around Gamma1 Leonis A, the brighter and more massive component of the Algieba binary system.
Characteristics Gamma1 Leonis b is classified as a super-Jupiter, meaning it has a significantly greater mass than Jupiter. Its minimum mass is estimated to be approximately 8.78 times that of Jupiter. It orbits its host star at an average distance of about 1.19 Astronomical Units (AU), which is slightly farther than Earth's orbit around the Sun. Its orbital period is approximately 429 days (about 1.17 years), and it follows a nearly circular path with a low eccentricity. Due to its large mass and likely gaseous composition, it is not considered to be habitable.
Host Star System Gamma1 Leonis b orbits Gamma1 Leonis A, which is a giant star of spectral type K0 III. This star is the brighter component of the Gamma Leonis (Algieba) binary system. The companion star, Gamma2 Leonis, is a G7 III giant, orbiting Gamma1 Leonis at a much wider separation of about 170 AU, with an orbital period estimated to be over 500 years. The presence of a planet orbiting one component of a wide binary system like Algieba provides valuable insights into planet formation in complex stellar environments.
Nomenclature The name "Gamma1 Leonis" refers to the primary star in the system according to the Bayer designation. The "b" suffix, following standard exoplanet naming conventions, denotes the first exoplanet discovered orbiting that star. While Algieba is the traditional name for the entire Gamma Leonis system, the planet is specifically designated Gamma1 Leonis b to indicate its association with the primary star component.