Thursday, October 25, 2012

AC B's P

To spell it out, our closest solar neighbor, Alpha Centauri, has three suns. Of these Alpha Centauri A is the biggest; it is about 10 percent more massive and 52 percent more luminous than our sun. It is about 4.4 light years from our sun. Alpha Centauri B is nearly as big as our sun (90.7%) but significantly less luminous (44.5% of the sun). This post is here because quite recently a Swiss astronomical team, headed by Xavier Dumusque, at the Geneva Observatory, discovered an earth-size planet orbiting a Cen B (to use a naming convention from astronomy). They published their findings in Nature on October 17 of this year. A and B are quite close to each other—the nearest distance between them is 900 million miles. The third sun that forms this system, known as Proxima Centauri, is the smallest (about 12.5% of the sun) and circles the AB twins at a trillion-mile distance. For that reason, periodically, it is the closest to the earth.

Our interest, of course, is in that unnamed planet, the P of my title. The current scientific consensus is that planets must be circling distant suns. One might say obviously. Seen in the frame of science, we are just a random sample, and if our sun has planets, others must have them too. But science is cautious, and rightly so. For decades, though, a search has been underway; in the course of it several gigantic, Jupiter-sized bodies have been discovered. a Cen B’s P, not named thus far, is the first of the right size. Alas, it orbits B at a distance much closer than Mercury circles our sun. For this reason the size is right but nothing else is. If there is life there, it has to take the form of fire demons.

Somewhere, surely, as probabilities dictate, there must be a planet of earth’s size and density, at the right distance from its sun, one neither too hot nor too dim to support life, with the same endowments of gas and water as ours, in existence just the right amount of time—to produce life spontaneously. And then, life once given, inevitably (given time and happy accidents enough), intelligent life will have evolved.

That is why we are interested in P.

Much food for thought. As this most recent addition to our knowledge shows, the improbability of life is a good deal higher than its inevitability. But there are those billions of galaxies filled with billions of stars. So, surely… Here and there, I assume, there are contrarian views. And vive la différence. Something even more improbable may be life’s explanation than all that we can possibly discover by microscopes and telescopes.

I show the same graphic, an artist’s rendition, everybody else does, courtesy of Wikipedia (link); that crescent on the right is P; B looks much bigger than A, but that is due to perspective. And my hat tip, and thanks, go to John Magee of eagle eyes and bottomless energy. He pointed me to this phenomenon and—amusingly—on a day when the Tigers were still struggling and the spin on the debates still raged. The subject of his e-mail? “The actual big news yesterday…”

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