Over the past 15 years much planet-hunting has focused on simply cataloging individual worlds whirling about other stars. This search was turbo-boosted last week. Two teams of astronomers reported that they are at the point where they can study the architecture of entire planetary systems.
By being able to characterize entire planetary systems — from Jovian gas giants to Earth-sized planets — we will gain important insights into the construction of alien solar systems in our galactic neighborhood.
In what seemed like a battle of press releases, last Tuesday the European Southern Observatory announced that five confirmed planets are circling the sun-like star HD10180, which is just 27 light-years away in the southern constellation Hydrus.
Two days later, NASA's Kepler space observatory reported possibly three planets (two of which have been confirmed) around a star called Kepler-9, which is a whopping 2,000 light-years away in the summer constellation Lyrae. Two of the confirmed Kepler planets are the size of Saturn. This adds to the fifteen planetary systems known to have at least three planets.
I find the HD 10180 system more intriguing than Kepler-9 because it has five Neptune-mass planets huddled close to the star — within the radius of Mars’ orbit. The outermost of these, HD 10180g, is within this star’s habitable zone where liquid water would remain stable. Though the planet is a 24 Earth-mass gas giant, it probably has a family of moons. Some may be big enough to be habitable by possessing an atmosphere and seas. This might be a great place to go looking for the blue-skinned "Avatar" aliens.
We see stark similarities and differences when comparing both systems to our solar system. The layout of the worlds offers insights into the assembly and evolution of planetary systems:
The mapping of these two systems will also allow us to eventually put our solar system into a broader context and determine how typical it is among what seems to be incredible diversity among planetary systems.
HD 10180 would be an intriguing system for a far-future interstellar probe to reconnoiter. The artificially intelligent machine would be like the Saturn Cassini mission on steroids. The probe would tour all the moons and planets in HD 10180. It would obediently send back streams of spellbinding pictures to the descendants of its earthbound builders — who would have to patiently wait 27 years for the first snapshot following the probe’s arrival. The probe might dispatch nanobot landers to do biology experiments on the surfaces of earth-like moons.
No doubt other bizarre and wondrous stellar systems await planet-hunters. It's a booming industry.