I remember talking to the exuberant astrophysics professor Sheridan Simon about a football-shaped planet he had created one Super Bowl eve. This was at a science fiction convention and it must have been fifteen years ago. Simon frequented such venues because he had built a cottage industry around creating planets for various science fictional settings. As a lark, he had run the numbers on what would happen to the atmosphere of a world shaped like a pigskin and wound up announcing the result: “It’s plaid! That’s what you would see. A plaid football!”
I think he was pulling my leg, and that wouldn’t have been out of character either for this generous, gregarious man who died all too young. But Mike Brown’s new paper in Nature brought back memories of that conversation with Sheridan Simon in spades. Brown (California Institute of Technology), who specializes in the exotica at the fringes of our Solar System, has been examining an object his team originally found. 2003 EL61 is also shaped like a football, though having no atmosphere, it doesn’t offer as many opportunities for fun as Simon’s planet did.
Brown now believes this Kuiper Belt object was the result of a catastrophic collision sometime around the time Earth was born. The original KBO was doubtless spherical and of roughly Pluto size until it was rammed by a body not much smaller than itself. The rapdily spinning (every four hours) football shape we see today is the result, along with two moons and many other fragments that have long since dispersed.
2003 EL61 plays interestingly into our understanding of how the Solar System evolved. For the area of space we’re talking about isn’t very stable. Here’s Brown on the matter:
“In most places, things go around the sun minding their own business for 4.5 billion years and nothing happens. But in a few places, though, orbits go crazy and change and eventually objects can find themselves on a trajectory into the inner solar system, where they would be what we would then call comets.”
So many of the shattered pieces of 2003 EL61 doubtless made their way in close to the Sun, and Brown believes some have probably hit the Earth at one time or another. And 2003 EL61 itself may become what Brown calls ‘…the largest comet in eons,’ although this won’t happen for a billion years. How big? Brown figures the incoming football will shine about 6000 times brighter than the Hale-Bopp comet did just a few years ago. If Sheridan Simon were still around, he could have some fun with that.
The paper is Brown et al., “A collisional family of icy objects in the Kuiper belt,” Nature 446 (15 March 2007), 294-296. Abstract here.