Weighing the Kuiper Belt
The measurement was made with an unusual instrument – the Cassini spacecraft observing Saturn “An understanding of the masses of these TNOs would help to pin down any gravitational interactions from Planet Nine”
ar away in the gloomy, distant suburbs of the outer Solar System, beyond the orbit of Neptune, lies a whole swarm of small, icy bodies. These trans-Neptunian objects (TNOs) mostly orbit at a distance of between about 30 and 50 astronomical units (AU) from the Sun – where 1 AU is the distance between the Sun and Earth. They make up the Kuiper Belt, a diffuse disc some 20 times wider than the asteroid belt and around 100 times more massive.
As more and more TNOs have been discovered, something very strange has been noticed; one group of TNOs cluster together and all make their closest approach to the Sun in the same sector. In 2016, an unseen ninth planet was proposed to explain these curious anomalies – a super-Earth orbiting at over 400 AU, whose gravity is shepherding these Kuiper Belt objects. Attempts to locate this elusive potential planet have so far failed, but what would really help pin down any gravitational interactions from Planet Nine is a much clearer understanding of the masses
Fof Saturn to metre-level accuracy. This is a staggering degree of precision and has enabled them to create one of the most accurate planetary ephemeris tables ever produced. So good, in fact, that they have been able to compare the actual orbital path of Saturn with predictions to determine how much Saturn’s orbit has been perturbed by gravitational interactions from the Kuiper Belt. Taking into account the nine particularly large TNOs that are known about, and a series of three rings within the Kuiper Belt, Di Ruscio estimates that the total mass of the Kuiper Belt is around 3.6 x 1023 kg – or about 6 per cent that of Earth.
With this knowledge now in hand, astronomers will be able to calculate a much better picture of how this Kuiper Belt is being disturbed by a ninth planet, and where to look for it – if it does exist!
was reading… Analysis of Cassini radio tracking data for the construction of INPOP19a – A new estimate of the Kuiper Belt mass Read it online at: https://hal.archives-ouvertes.fr/ hal-02881391