NASA has published an image captured by its New Horizons space probe in which its LORRI instrument detected Ultima Thule, the Kuiper belt object – but there may be two objects and/or a moon – that represents its next target for a flyby scheduled for New Year’s Day 2019. When the 48 photos combined in the image were taken, on August 16, 2018, New Horizons was still about 172 million kilometers (107 million miles) from Ultima Thule and being able to identify its target is positive because mission managers can start assessing any adjustments to the probe’s course.
Ultima Thule is an unofficial nickname of the Kuiper Belt Object officially cataloged as 2014 MU69 announced by NASA in March 2018. Precisely because it’s not clear whether it’s a single or multiple object, at the moment it’s not possible for the International Astronomical Union (IAU) to ratify any name.
So far, the observations of Ultima Thule have been conducted in particular with the Hubble Space Telescope and some with the SOFIA flying telescope, instruments that only for a few years have been following this object, providing astronomers with information to reconstruct its orbit. This is an important task to set the New Horizons space probe’s route but the data are still limited. The consequence is that finding Ultima Thule for New Horizons with the instruments on board is even more important to understand first if the object is where expected and if the probe’s course need to be adjusted.
The Long Range Reconnaissance Imager (LORRI) instrument was used to search for Ultima Thule, which appeared as a dim object in photos taken on August 16, 2018. Hal Weave, principal investigator of the LORRI instrument, explained that for NASA scientists it was like looking for a needle in a haystack with the additional difficulty of having a star in a position near Ultima Thule and about 17 times brighter. To find the “needle” it was useful to have previous photos of the “haystack”, taken by LORRI in September 2017, which allowed to determine which light sources were stars.
The image (NASA/JHUAPL/SwRI) shows on the left side the image consisting of 48 photos taken by LORRI and then sent to Earth, where they were processed and combined. The yellow square surrounds the area containing Ultima Thule, enlarged on the right side, where the light of the various visible stars has been eliminated, leaving Ultima Thule in the center of the yellow crosshairs.
Alan Stern, New Horizons principal investigator, pointed out that determining if Ultima Thule was detected by the LORRI instrument was a difficult task but the result was positive. This confirmed that the calculations of its orbit based on the data collected by the Hubble Space Telescope were correct.
In this period, Ultima Thule is about 6.5 billion kilometers (4 billion miles) from the Sun. The New Horizons space probe is getting progressively closer to its target so it will get easier and easier to identify it until the point where it will be possible to start seeing its feature in a mission that’s really reaching the final frontier.