Thursday, November 08, 2007

OT: Planets Like Ours

I saw this news item and wanted to pass it on as fuel for thought for all of us SF authors.


Solar system “packed with planets” looks like our own

Nov. 6, 2007
World Science staff

As­tro­no­mers say they have found a dis­tant so­lar sys­tem that looks more like ours than do any of the others known. Though it lacks any ev­i­dence of hab­it­a­ble worlds, they added, some might turn up there.

It’s the “first quin­tu­ple plan­e­tary sys­tem,” and may have as yet-unde­tected Earth-like plan­ets or hab­it­a­ble moons, said San Fran­cis­co State Un­ivers­ity as­tron­o­mer Deb­ra Fisch­er, a mem­ber of the re­search team.

It seems to be “packed with plan­ets,” as ours is, she added. All the plan­ets de­tected there are much heav­i­er than Earth, she not­ed, which poses prob­lems for their hab­it­abil­ity. But Earth-sized plan­ets, prac­tic­ally un­de­tect­a­ble out­side our So­lar Sys­tem with cur­rent tech­nol­o­gy, could easily have gone un­no­ticed.

The find­ing “has me jump­ing out of my socks,” said Ge­off Mar­cy of the Un­ivers­ity of Cal­i­for­nia, Berke­ley, an­oth­er mem­ber of the re­search team. The group an­nounced the find­ings at a press con­fer­ence in Pas­a­de­na, Ca­lif. Tues­day.

The dis­cov­ery sug­gests so­lar sys­tems much like our own are com­mon, he added. “Our Milky Way gal­axy, with 200 bil­lion stars, con­tains bil­lions of plan­e­tary sys­tems—many as rich as our own,” he said. “We strongly sus­pect many of these har­bor Earth-like plan­ets.”

More than 250 plan­ets out­side our sys­tem are known, but most of them are in so­lar sys­tems or in ar­range­ments that would seem to make it hard for life to form there.

A pos­si­ble ex­cep­tion was an­nounced last April with a re­port that a plan­et or­bit­ing the star Gliese 581 might be hab­it­a­ble. But as­tron­o­mers have be­gun de­bat­ing wheth­er that’s the case, ac­cord­ing to Fisch­er’s team. It’s very tricky to de­fine a star’s “hab­it­a­ble zone,” the re­gion around it with the right tem­per­a­tures for liq­uid wa­ter to ex­ist, Mar­cy said.

The new find­ings—involving the star 55 Can­cri, visi­ble with bi­no­cu­lars in the con­stella­t­ion Can­cer—do re­veal a hab­it­a­ble-zone plan­et, they added. But it seems too large for life as we know it to take root there: it weighs the equiv­a­lent of an es­ti­mat­ed 45 Earths, which sci­en­tists say would probably make it a gas gi­ant like Sat­urn, though smaller.

“Such plan­ets are probably not hab­it­a­ble,” Mar­cy said; but it might well have hab­it­a­ble moons that re­main to be found. “If there is a moon or­bit­ing this new, mas­sive plan­et, it might have pools of liq­uid wa­ter on a rocky sur­face,” said Fisch­er. The hab­it­a­ble-zone gi­ant is about as far from its star as Ve­nus is from the Sun; but it would be cool­er than Ve­nus be­cause the star is some­what smal­ler and fainter than ours, the re­search­ers added.

The oth­er plan­ets around 55 Can­cri, whose whole plan­e­tary co­te­rie took 18 years to dis­cov­er, are also giants, they said. Re­search­ers dis­cov­ered the worlds us­ing the Dop­pler tech­nique, in which a plan­et’s gravita­t­ional tug is de­tected by the wob­ble its gra­vity pro­duces in the par­ent star.

A key fea­ture of the new­found sys­tem is that most of its worlds have near-circular or­bits around the star, Fisch­er said. That’s im­por­tant be­cause it means they would­n’t suf­fer dras­tic tem­per­a­ture varia­t­ions at dif­fer­ent times of the year; rath­er, their tem­per­a­ture fluctua­t­ions would be more or less equiv­a­lent to those of our sea­sons. The 55 Can­cri sys­tem also re­sembles ours in terms of its ap­prox­i­mate size, the re­search­ers said. A pa­per on the find­ings is to ap­pear in The Astro­phy­si­cal Jour­nal.

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