Planet Nine
Scientists observed some very strange behaviour at the edge of our solar system, and the only possible explanation is that there is another planet which is 9th.
No one has seen this planet, but we have seen its gravitational influence. The scientists modelled the hypothetical planet’s gravitational effects on several known bodies in the region and found a near perfect match, which they described as a jaw-dropping moment.
For the observable effects to occur, the planet would be about 10 times bigger than Earth and be much farther than Neptune on a very elliptical orbit. The next scientific discovery now remains to observe the planet directly.
Difficult words: observe (to watch), influence (power), body (space object), jaw-dropping (amazing), elliptical (like an ellipse – narrow circle), orbit (a long, circular journey).