New Horizons is on its course toward Pluto and its moons, and with the images that it has captured so far, scientists are wondering why Ultima Thule, a trans-Neptunian object located at the Kuiper Belt lacks a light curve.
Even though scientists determined in 2017 that the Kuiper Belt object isn't shaped like a sphere – that it is probably elongated or maybe even two objects – they haven't seen the repeated pulsations in brightness that they'd expect from a rotating object of that shape.
The periodic variation in brightness during every rotation produces what scientists refer to as a light curve.
Read more on the New Horizons site.
(Image credit: NASA/JHUAPL/SwRI)