Their existence sheds light on how planets formed. New Horizons has detected pairs of binary Kuiper belt asteroids in the outer solar system
New Horizons has discovered two Kuiper belt objects that are, in fact, pairs of binary asteroids. The announcement was made at the 53rd meeting of the American Astronomical Society's Division of Planetary Sciences. The nearby binary pairs have been named 2011 JY31 and 2014 OS393. The objects were first spotted by ground-based observatories, then New Horizons' Long-Range Reconnaissance Imager (LORRI) camera captured them in September 2018 after a flyover of Pluto while en route to Arrokoth.
Images of the two strange asteroid pairs
The high-resolution LORRI imager is equivalent to an 8-inch reflector telescope familiar to many astrophotographers. To be considered for the study, the objects, when targeted, had to be within 0.3 astronomical units of New Horizons' path. Both 2011's JY31 and 2014's OS393 appeared slightly elongated in the images compared to a nearby star.
The team of scientists fitted the shapes with a two-body model: two asteroids in a narrow orbit. The modeling showed that two bodies were better able to explain the elongation, as well as the brightness seen. The model for 2011 JY31 had two 50-km-wide objects nearly 200 km apart, while for 2014 OS393, the model had slightly smaller bodies (30 km in diameter) orbiting each other 150 km apart.
How the asteroid pairs formed
The orbiting twins would have formed in situ and support a formation model in which gentle, low-velocity collisions between small objects, or "pebbles," produce denser clouds filled with pebbles that then collapse into larger planetesimals, such as their binary contacts (like Arrokoth) or their close twins (i.e., the other two asteroids).
Launched from Cape Canaveral on January 19, 2006, New Horizons visited Pluto in 2015, then flew 2,200 miles past Arrokoth on New Year's Day 2019. Since then, the team of researchers has been studying objects in the area.
In addition to the pair of binary asteroids, a rare half-asteroid, half-comet object has also been identified in our solar system. Some scientists, instead, have identified that on some small asteroids there are iron, nickel and cobalt and they are finding a way to extract them.