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.

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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.