For a long time it was assumed that it was impossible or near-impossible to have stable planets in systems with two suns orbiting one another. However, a few years ago the first such systems with planets were discovered, and today New Scientist reports that it is in fact those binary systems where planets can be found with a greater probability than for example in solar systems with just one sun.
This is, of course, good for those who promote the idea that Earth has been repeatedly visited by Aliens from Sirius, which is a system with at least two, and possibly three, stars. Whether it in practice makes their case any stronger, I don’t know.
The feud about the number of planets is starting to calm down, as New Scientist reports that the latest, and so-far best received, proposal is to demote Pluto and simply say that the definition of a planet is a significantyl large object which is “the dominant body in its orbital zone”.
This makes me wonder what happens if we discover twin planets, where two planets orbit one another, as well as their sun.
It also makes me wonder what the new mnemonic is going to be for the solar system. “My Very Excellent Mother Just Sent Us Nine Pizzas” used to be the trick to remember the order of the nine-planet solar system (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto), but obviously the sentence will not make any sense if Pizza is omitted. A recent Language Log article actually set out to construct a mnemonic for the original proposition that included thirteen planets: My Very Excellent Mother Could Just Send Us Nine Cheerleaders Playing Xylophones. I remain waiting for their suggestion about the non-Pluto mnemonic.
For years now a war has been raging among astronomers about the definition of a “planet”. As BBC news reports, some sort of a solution is attempted next Tuesday, when experts gather in Prague to vote for a definition that would not only keep Pluto, but also include its twin Charon, the larger object 2003 UB313, as well as the largest asteroid, Ceres.
If the vote is passed, it would potentially open a can of worms, as the list of planets in our solar system would suddenly not be fixed, and new planets could be “discovered” as the new definiton would be applied to bodies found in the Kuiper belt. My opinion, therefore, would be to just keep the list of planets as it is, and decide that Pluto is on the list because of historical reasons. This may not be very scientific, but then again I’m not sure whether the whole issue is a scientific one, or rather one of purely linguistic nature.
