{{DISPLAYTITLE:Eta2 Hydri}} Eta2 Hydri, Latinized from η2 Hydri and often catalogued as HD 11977, is a star in the constellation of Hydrus. It is visible to the naked eye with an apparent visual magnitude of +4.68, and is one of the least variable stars known. The distance to Eta2 Hydri is approximately 222 light-years based on parallax measurements, but it is drifting closer to the Sun with a radial velocity of −18 km/s. The stellar classification of Eta2 Hydri is G8IIIb, which indicates this is a evolved giant star. It is located in the clump zone of the HR diagram, which indicates it has already ascended the red giant branch and is now generating energy by core helium fusion surrounded by a hydrogen fusing shell. Based on its mass, it was probably a class A star (similar to Vega or Fomalhaut) when it was on the main sequence. It is estimated to be around 1.3 billion years old and has expanded to 10 times the Sun's diameter, though is only around 1.9 times as massive as the Sun. The star has a leisurely rotation, with a period of no more than 230–270 days. As of 2005, an extrasolar planet was confirmed to be orbiting the star. Planetary system In 2005, the giant planet Eta2 Hydri b was found in orbit around Eta2 Hydri by measuring radial velocity variations. This object has at least 6.3 times the mass of the Sun and is orbiting with a period of . It is the first giant planet to be found in orbit around an intermediate-mass giant star. See also HD 11964 References External links G-type giants Horizontal-branch stars Planetary systems with one confirmed planet Hydrus (constellation) Hydrus, eta2 Durchmusterung objects 011977 008928 0570