This prompted the Bern team, Prof Christoph Mordasini and Esther Linder, to use computer simulations to work out basic characteristics for the hypothetical ninth planet.

The Bern-based astrophysicists assumed that Planet Nine was a smaller version of Uranus and Neptune – a small ice giant with an envelope of hydrogen and helium.

Using their planet evolution model, they calculated how parameters like the planetary radius or the brightness evolved over time since the Solar System formed 4.6 billion years ago.

Their results suggest that for a planet 10 times more massive than Earth (the estimate obtained by Brown and Batygin), it would have a diameter 7.5 times bigger than our planet’s. They also estimate that its temperature would be an icy -226C (-375F).