The object does not yet have a formal name; it is called "1110113Y" on the Hubble website and "PT1" within the New Horizons team. Another numerical designation will come after the object is submitted to the Minor Planet Center, which the search team says it will do after they perform followup observations with Hubble in October to pin down the astrometry more precisely. Eventually, it will get a provisional name (2014 followed by some letters and numbers) from the Minor Planet Center. Hopefully it will get a formal name before January 2019, which is when New Horizons will fly past it.

Although PT1 is the most likely of the Hubble-discovered objects to be targeted, it's possible that followup observations may make PT2 or PT3 more desirable. PT2 and PT3 are both slightly brighter than PT1 and are therefore probably larger. Unfortunately, it's not possible to target two of these objects within New Horizons' fuel budget; they must select one.

What do we know about PT1 so far? Its orbit is circular and close to the plane of the ecliptic, so it is a Cold Classical Kuiper belt object, meaning that it has had a very different history from Pluto. Pluto is a member of a population of objects in the Kuiper belt whose orbits were changed as Neptune migrated outward, scattering them. Pluto now has an inclined and elliptical orbit that is locked in a resonance with Neptune, such that Pluto orbits the Sun twice for every three times Neptune does. In contrast, Cold Classical objects were probably never tossed around in this way. So PT1 could be very pristine, a cold, never-heated relic of solar system formation. On the other hand, it's very small, estimated to be 30 to 45 kilometers in diameter, and scientists think that most objects of that size are not primordial, but are actually fragments from collisions of larger objects, which would make it less pristine. No matter what, its size and orbital position mean that it will look very, very different from Pluto.