After the New Horizons spacecraft made its historic flyby of Pluto in July 2015, the plan was always to send it further out of the Solar System to study other objects. Now, the spacecraft has returned the first science from such observations.
New Horizons observed a Kuiper Belt object (KBO) on two separate occasions called 1994 JR1, which measures 145 kilometers (90 miles) across. KBOs are remnants of the early Solar System, in the form of icy comets and asteroids, so studying them could reveal important clues about our beginnings.
These observations weren’t comparable with the Pluto flyby though, when New Horizons flew just a few tens of thousands of kilometers above the surface. Instead, New Horizons snapped the KBO from a distance of 111 million kilometers (69 million miles) in early April, following preliminary observations from more than twice as far away in November 2015.
But this post-Pluto science is important, because it helps New Horizons practice for a more ambitious mission in 2019. On January 1 of that year, mission scientists will send New Horizons flying past a KBO called 2014 MU69 closer than it came to Pluto, although the exact flyby distance is not known yet.
As for JR1, well, we did actually learn a bit from these views. First, scientists were able to pinpoint its location to within 1,000 kilometers (621 miles), the most accurate for any small KBO. This allowed them to rule out a theory that JR1 might be a distant satellite of Pluto. They were also able to work out JR1’s rotation speed, clocking it at one rotation every 5.4 Earth hours.
Above, an animation of JR1 moving from two of 20 observations made in April 2016. Top left is an internal camera reflection, which NASA calls "a kind of selfie." NASA/JHUAPL/SwRI
“That’s relatively fast for a KBO,” said science team member John Spencer, from the Southwest Research Institute (SwRI) in Colorado, in a statement. “This is all part of the excitement of exploring new places and seeing things never seen before.”
Before New Horizons reaches 2014 MU69, it will study about 20 more KBOs, pending approval for this extended mission from NASA (which seems a done deal at the moment). Pluto may have been impressive, but these endeavors will tell us even more about the outer Solar System than ever before.