Thursday, February 3, 2011

Solar System K-11 Now Identified!




Even as the tally of catalogued extra-solar planets reaches 1200, the NASA Kepler space mission has scored another monumental find - trumping all others hitherto. That is, Kepler has identified a full solar system (dubbed "K-11") bearing at least six small planets orbiting a narrow "ecliptic plane" like most of the planets of our own. At least one of these appears to be in the "Goldilocks" or habitable zone, such as we find Earth. (The reader can compare the scales of the Kepler-11 solar system and our own from the graphic).

This orbital confinement to a disc-like plane is critical because it suggests a similar initial formation from a collapsing protostellar dust and gas cloud. The central region then collapsed under the influence of gravity to become the star ('sun') while the planets were hurled off in concentric dust and gas rings that condensed to become each of the separate worlds. In the process, as with our own system, angular momentum was also transferred from the central rotating mass to impart spin (axial rotation) to each of the worlds.

However, in the K-11 system all the planets are believed to be gaseous rather than rocky (like the Earth or Mars) suggesting also they are at an earlier phase of formation- and it is unlikely any life forms would be found there. Despite that, the find has aroused intense interest in what else may be out there.

According to Jonathan Fortney, a member of the Kepler science team based at the University of California at Sant Cruz:

"This is a remarkable system and a very exciting sign of what else is to come!"

He added:

"Given the information Kepler is sending back, we're not only able to identify the planets, but we can tell a lot about how big they are, how close they are to their suns and to some extent what they're made of".

This is indeed remarkable, and the Kepler total results (published in the journal Nature) document barely a quarter of the total information constellation collected by Kepler which was launched nearly two years ago. Its main function and objective is to observationally document how many Earth-sized planets exist in a particular segment of space and how many suns are like our own (G2 spectral type). It also seeks to assay how many total planets (especially Earth-sized) are found in habitable zones. The ultimate goal is to assess whether any of the found planets can or might support life.

Owing to the techniques used by Kepler most of the planets identified so far are rather closer to their suns than Mercury, hence outside the Goldilocks zone. However, it's expected that as Kepler collects data over a longer time planets farther from their suns will be identified - and these (because of the increased distance) would more likely to be rocky planets.

The technique used is illustrated in the second graphic which I sketched - showing a planet passing in front of its central star. We call such a passage a "transit". In the course of the planetary body covering a small fraction of the stellar disc in transit, the light curve brightness (B) is slightly reduced. The fraction of reduced brightness enables astronomers to estimate the size of the planet in terms of the stellar radius while the time between such transits reveals the speed of the planet in its orbit.

Stay tuned!

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