Editing Mu Arae (section)

=== Discovery ===
In 2001, an extrasolar planet was announced by the [[Anglo-Australian Planet Search]] team, together with the planet orbiting [[Epsilon Reticuli]]. The planet, designated [[Mu Arae b]], was thought to be in a highly [[eccentricity (orbit)|eccentric]] orbit of around 743 days.<ref name=Butler_2001/> The discovery was made by analysing variations in the star's [[radial velocity]] (measured by observing the [[Doppler shift]] of the star's [[spectral line]]s) as a result of being pulled around by the planet's [[gravity]].  Further observations revealed the presence of a second object in the system (now designated as [[Mu Arae e]]), which was published in 2004. At the time, the parameters of this planet were poorly constrained and it was thought to be in an orbit of around 8.2 years with a high eccentricity.<ref name="McCarthy2004"/> Later in 2004, a small inner planet designated [[Mu Arae c]] was announced with a mass comparable with that of [[Uranus]] in a 9-day orbit. This was the first of the class of planets known as "[[hot Neptune]]s" to be discovered. The discovery was made by making high-precision radial velocity measurements with the [[High Accuracy Radial Velocity Planet Searcher]] (HARPS) [[spectrograph]].<ref name="santos"/>

In 2006, two teams, one led by [[Krzysztof Goździewski]] and the other by [[Francesco Pepe]] independently announced four-planet models for the radial velocity measurements of the star, with a new planet ([[Mu Arae d]]) in a near-circular orbit lasting approximately 311 days.<ref name="gozdziewski"/><ref name="pepe"/> The new model gives revised parameters for the previously known planets, with lower eccentricity orbits than in the previous model and including a more robust characterization of the orbit of Mu Arae e. The discovery of the fourth planet made Mu Arae the second known four-planet extrasolar system, after [[55 Cancri]].