Nasa’s New Horizons spacecraft is making good progress towards its next target, an elongated mini planet which may actually be two smaller worlds in orbit around one another.
Since New Horizons made the first ever flyby of Pluto, in July 2015, the spacecraft has been heading into the depths of the solar system. This region is known as the Kuiper belt, and, rather like an icy asteroid belt, is the home to a large collection of celestial objects.
For learning as much as possible, in preparation for the flyby, this tiny world had been the subject of an intense observational campaign from the Earth.
Astronomers had already adjusted New Horizon’s trajectory to fly past Kuiper belt object 2014 MU69. On 17 July this year, 2014 MU69 passed in front of a star briefly blocking out its light. The event was visible from Argentina and astronomers deployed mobile telescopes in Chubat and Santa Cruz to capture the moment from the two locations.
Observing with these different lines of sight allowed the team to compare their data and use the information to indicate the shape of the object.
The results announced this week show the team found that 2014 MU69 had to be extremely elongated and that it could even be a pair of small worlds orbiting one another. It was calculated to be no larger than about 30km across.
Astronomers are increasingly finding that comets and Kuiper belt objects are double systems. This suggests they fell together gently rather than had the kind of high-energy collisions that formed the planets of Earth and Mars.
Their gentle collision speeds meant they preserved the chemicals that were present at the beginning of the solar system. New Horizons will analyse these as it flies past 2014 MU69 on 1 January 2019.
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