Looks like Pluto’s got some competition.
Two sets of astronomers have spotted a new planetoid in the outskirts of our Solar System. It is the brightest object in the region after Pluto, and it has its own small moon.
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In recent years astronomers have spotted several Kuiper-belt planetoids, including ones named Quaoar and Varuna; the latest has been nicknamed Santa. Philosophical debates continue about how large such objects have to be before we call them ‘planets’ rather than simple lumps of rock
Funny, I thought the earth was simply a lump of rock. Am I wrong? Is the earth really made of cheese or some other non-rock substance? And what’s with the philosopher bashing? Surely philosophers do more than just debate what one should label a planet! 😉
Pluto and Santa look like they were not formed in the same way as the first eight planets. The first eight planets are all in the same plane and all have round orbits. They are also large and made of gas or medium-sized and made of rock. These objects are smaller, further away, have more elliptic orbits, are out of plane, and are probably made of ice.
Okay, you could count every solar system object like that a “planet”; but then there would be billions of them. Probably the only logical rescue for the terminology is to disqualify Pluto.
From a completely civilian point of view, I’m guessing that the average mildly educated reader intuitively thinks that planets have “days”. Personally, I very unreasonably sort of unreasonably associate “molten core” with non-Gaseous planets. I think there’s evidence that the four terrestrial planets all have/had one. Lump of rock sort of implies solid all the way through, perhaps not round and therefore possibly not spinning at a regular rate.