Ultra

Ultra is a planet located in an area of space relative to the outer Solar System, but off the plane of the ecliptic almost by 40 degrees. The planet, which had never been seen prior to it's discovery by Victor Bergman in 1994, is thought to have originated outside the Solar System.

The Ultra Probe (aka Astro 8) was launched to investigate Ultra on June 6th 1996, only for contact to be lost when it arrives in February 1997.

Trivia
There are two different dates for the planet's discovery - June 23rd in the Shane Johnson Timeline, and August 8th in the Kevin McCorry Timeline.