The unknown fifth giant planet

New research from an astronomer at the Southwest Research Institute (SRI) in San Antonio suggests that our solar system family at one point had an additional member to it...and it was an enormous one.

That's right.  Another giant up there in the leagues of Jupiter, Saturn, Neptune, and Uranus.  I'll pause a moment to let the snickers die down from the name of that last planet.

Computer models by David Nesvorny at SRI appear to lead to the notion that current orbital layout of our solar system had only a "2.5%" chance of becoming the way it is without a fifth giant planet.

He said: "The possibility that the solar system had more than four giant planets initially, and ejected some, appears to be conceivable in view of the recent discovery of a large number of free-floating planets in interstellar space, indicating the planet ejection process could be a common occurrence."

From this standpoint, it is thought that Jupiter once drifted towards the center of the solar system and approached the orbits of Mars and our own Earth.  The gas giant was rapidly yanked backward, however, and this had the effect of knocking the fifth unknown giant planet out into deep space.  This all probably happened during the period where planets were just forming in the solar system and nothing in the system was entirely stable.  So the event was something of a cosmic miscarriage.

Makes me wonder what the absent planet would have been like.  What would we have named it?  How bright would it have been in our sky?  What would its unique features have been?  Gives me the germ of a short story idea wherein our solar system still has this unknown, fifth giant.

Yet most disconcerting of all in the above linked article is the fact that our Sun is already halfway through its life expectancy.  Not for fear of imminent supernova but because this will doubtless inspire the various end-of-the-world types out there.

Bring on talk of Rapture and 2012!


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