Pregnant Young Sun

A story in today’s Wall Street Journal (link) reports on the discovery of what may be a new planet forming in the gaseous disk surrounding a young sun quite near us in the Milky May. Near is 335 light years from here. The sun’s name is HD100546. The “planet” is an asymmetry in the gas disk; the point where the asymmetry is observed also emits strong radiation. I note this here for future reference. Of the two theories of planet formation, one has particles, large and small, colliding and cohering as they circle a sun and then, slowly, aggregating into planets. This would suggests that the asteroid belt in our own system has simply failed to “get with the program.” The other model is that planet formation is a spontaneous process that takes place in the wake of a star's own formation—the planets forming, much as the one reported today, from the same raw materials that gave birth to the sun and soon after—thus while a good deal of dynamism is moving that disk of gases and dust. I’ve long favored this second view—and prefer to imagine that the asteroid belt is the record of some planet that got shattered in some collision. The discoverer here is Sascha Quanz, of the ETH University in Switzerland, working with his team at one of two observatories operated by the European Southern Observatory in the Atacama Desert of Chile. The one used was not reported but was probably Paranal, the location of the Very Large Telescope.

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…”