Five years since its historic flyby of Pluto and 18 months since meeting Arrokoth, NASA’s New Horizons is now involved in a new astronomical endeavor. Together with the Subaru Telescope, it will observe yet-to-be-discovered celestial bodies and maybe even visiting ones.

New Horizons is in a region of space known as the Kuiper Belt, which is believed to be rich in fragments of the Solar System’s formation known as small bodies. Despite large numbers of these objects, finding them is a challenge because they are tiny and spread out over large distances.

“We are using the Subaru Telescope because it is the best in the world for our search purposes. This is due to its unique combination of telescope size – one of the very largest anywhere – and Hyper Suprime-Cam’s (HSC) wide field of view, which can discover many Kuiper Belt objects at once,” Dr Alan Stern of the Southwest Research Institute, the principal investigator of the New Horizons mission, said in a statement.

The area being studied by Subaru’s HSC is equivalent to 18 full moons in the sky. Astronomers estimate that hundreds of new Kuiper Belt objects will be discovered in this way and about 50 will be observable with New Horizons.

Kuiper Belt objects from Subaru’s point of view will appear fully illuminated by sunlight. From New Horizons' perspective, it will be only partly illuminated as it is much closer to these objects than Earth. This difference will provide researchers with important data about these cosmic fragments.

“The search area is within the Milky Way, and thus there are many nearby stars including bright ones, which make the observations even more difficult. The observation team is doing its best to take high-quality data by utilizing the unique capabilities of the Subaru Telescope, and to investigate the origin of the Solar System together with New Horizons,” added Dr Tsuyoshi Terai, a core member of the observation team and a support astronomer for the Subaru Telescope in charge of HSC.

It is certainly possible that one of the newly discovered objects is in the right orbit for a future rendezvous with New Horizons. For example, Arrokoth was discovered in 2014, 12 years after the spacecraft was launched.

Even without another flyby, New Horizons continues to provide insight beyond its core mission of studying Pluto. Just last month, it was used to perform the furthest parallax experiment yet.