In the Solar System, the inner planets (Mercury to Mars) are rocky, and the outer planets (Jupiter to Neptune) are gaseous. This pattern – rock to gas – has been consistently observed across the Milky Way until now.

They did my boy Pluto dirty with this one.

But joke aside, it's a bit strange that they present this as so unprecedented when we have Pluto, a big rock (almost planet), orbiting outside the gas giants in our own system. I would think that very little would be required for Pluto to actually be considered a planet (just a slight bit more rocks and dust for it to collect and grow off), yet they still make it sound like the idea of a rocky planet existing outside the gas-planets was basically unheard of until now.