The Oort Cloud is a hypothetical, roughly spherical barrier over 50,000 AU (1 ly) from the Sun. This means that the outer reaches of the cloud are a quarter of the distance of the Sun to Proxima Centauri, the closest star to the Sun, which lies over 4,2 light-years from it. The Oort Cloud can contain up to a few trillion comets and lesser, but still large amounts of Trans-Neptunian Objects, such as Sedna or Tyche. Tyche was discovered in 2013 and is the 9th and outermost major planet. Tyche's gravitational pull causes the orbits of many comets to change, sometimes forcing them into the inner Solar System, creating impact effects with Earth, Jupiter, and Eris. Jupiter as impacted in 1994 by Comet Shoemaker-Levy. The outer Oort Cloud is the boundary of the Sun's gravitational influence.