New Horizons is a small spacecraft on its way to Pluto. It will make its closest approach next Summer. To get to Pluto in a reasonable time, the spacecraft is heading there at high speed. This means it will zip past Pluto and head out into the Kuiper belt. While Pluto is a worthy goal, it would be nice if New Horizons could observe other objects in the outer solar system. But given the high speed of the spacecraft, and the low mass of Pluto, there isn’t a good way to use the planet’s gravity to change direction towards a particular Kuiper belt object (KBO). Basically, New Horizons is on a straight trajectory out of the solar system. So instead astronomers have been searching for KBOs that are along the path of New Horizons, and they’ve found some candidates.
The three possibilities are KBOs known as PT1, PT2 and PT3. In this case PT stands for “potential target.” Of these PT1 is in best alignment with the trajectory of New Horizons, and thus would require the smallest delta-v adjustment. What’s exciting about this is that we haven’t had a good look at any Kuiper belt objects, given their large distance and small size. The closest we’ve got are moons such as Neptune’s Triton, which we think is a captured KBO.
If successful, New Horizons will make its flyby of PT1 in January of 2019.