Interstellar missions aren’t science fiction. They’re a plausible, but technically risky, option to consider.

Let’s say the star dims a bit after 50 days, and there’s a 50% chance that’s due to noise. Then the star dims again after another 50 days with the same odds of error. Now we can be 1-(2*50%) = 75% confident we’ve got a big orbiting object. After three such observations in a row, 87.5%, after four, 93.75%, and so on.

The error decreases exponentially, so with enough periods we can be extremely confident. Similarly, the error in the amount of brightness change (and thus in the inferred diameter) and in the amount of wobble (thus in the inferred mass) decreases rapidly with the number of observations.

As for how normal or odd our own solar system is, we have much left to learn to figure that out. I don’t take the studies of statistical distribution that have come out so far too seriously — e.g. the ones that try to extrapolate the data to estimate the number of earthlike planets — because of the selection biases we discussed above. With our own methods, we couldn’t rule out any unobserved planets at Kepler distances corresponding to any of the masses and orbital distances of any of the planets in our own solar system. Indeed most such planets in the Kepler sample region will probably remain undetected, and the vast majority not reliably detected (i.e. “planet candidates” only rather than announced discoveries). To detect more planets that are farther out or smaller we need more patience and a spacecraft that is much longer-lived than Kepler likely will be.

Googaw wrote @ October 20th, 2012 at 2:56 am

thank you both very much…yeah I see the method and assume what they are doing is scientifically and math rigorous, I saw some of the smoothed and raw data the other day.

I am just wondering (with no real information actually but just speculating) if what we are seeing is “noise” however and looking to hard at the data to find something.? Dont know and perhaps I am being to “solar system centric” but well the planet around AC would be “Vulcan” (the one they looked for in our solar system before relativity explained Mercury…

It just strikes me as odd…but then again our system might be odd.

I look forward to better “tubes”. RGO

That’s a great explanation for the Alpha Centauri detection and a large number of earlier exoplanet discoveries, and of the selection effect that produces a distribution of sizes and orbits in the observed planets very different from the actual overall distribution. Kepler uses a different method, the slight dimming of stars when their planets transit, but that method too is biased towards discovering larger planets. It’s also biased towards discovering planets with shorter orbits, albeit for different and partially fixable reasons — it requires several orbits (several transits) to get enough data to cut through the noise. There’s more such noise than expected, so it will take several more years of a Kepler extended duration mission or a follow-up mission to be able to reliably detect a significant fraction of the planets within its survey region that are near terrestrial in size and near one-year orbits. The vast majority of its discoveries will be larger and have much shorter orbits than that. Let’s hope Kepler’s remaining reaction wheels remain intact long enough!

It’s both the most interesting type of planet from our Earth-centric point-of-view, but it’s also among the most hardest type of exoplanet to find

To me this implies that we should be a bit more patient and a bit less earth-centric. In the meantime there are a ton of interesting and important things to be learned about the temperature, surface and atmospheric chemistry, etc. of super-Jupiters, cold Jupiters, hot Jupiters, hot and cold Neptunes, hot super-terrestrials, super-terrestrials in or near the habitable zone, hot rocky planets, large dust rings, etc. As well as from imaging some of the ones orbiting brighter stars with JWST etc.

It makes sense if you understand the detection method. They measure the wobble in the star’s spectral red/blueshift as the star gets pulled ever so slightly back-and-forth by the planets orbiting it. Really big planets and/or planets really close to their parent star are going to produce the biggest wobbles in those parent stars. And that’s all astronomers are able to detect right now — the really big wobbles in the parent stars — which skews the exoplanet population they’re able to confirm towards really big planets and planets really close to their stars. Although able to detect some exoplanets, our still-primitive, ground-based telescopes are acting like sieves, letting all the small grains of sand through and only capturing the big rocks. Until they’re able to field more sensitive telescopes, like WFIRST, astronomers won’t get a population of exoplanets that includes the more “normal” types of planets found in our solar system. And astronomers won’t really be able to define a “normal” solar system until they’ve taken a census or two with these more sensitive telescopes.

This is why finding a terrestrial planet in a habitable zone is such a holy grail for exoplanet astronomers. It’s both the most interesting type of planet from our Earth-centric point-of-view, but it’s also among the most hardest type of exoplanet to find, i.e., a relatively small planet a good distance from its parent star (which isn’t going to produce much of a wobble in that parent star’s spectrum).

Hope this helps.

Do you buy this? I am not in a position to intelligently discuss the methods and data used (but assume the people who make thestatements are)…it just strikes me odd that most if not all the planets we are discovering all are quite different from anything in our solar system? OK that could mean we are just ‘unique”…but there is nothing in our solar system that goes around the sun 3.X days…

comments? RGO

I’m all for miniaturization (and standardization) of robotic probes whereever it makes technical and economic sense. But absent a practical quantum communications device, it’s hard to see how a probe weighing grams could get a signal back to our solar system from light years away. Metamaterial antennas might allow a cubesat to transmit over interplanetary distances using laptop power. Pen-sized lasers could do theoretically same at very low bandwidths with large enough receivers (infrared telescopes) on Earth. But neither of these concepts is gram-sized or capable of operating over interstellar distances.

FWIW…

The problem with the starship propulsion research is that so far at least it is just slideware. They need to get into the laboratory to make and break things, however far from a real starship they may be. In the meantime there are likely to be practical applications in earth orbit — it’s many decades premature to be focusing on tech that could only be useful for starships.

require laser power approaching the 30 terawatt range sustained over 80-odd years

That’s why the other leg of this research, at least as important as the propulsion, and with even greater and more obvious practical application much closer to home, is miniaturization. We certainly won’t be boosting today’s spacecraft to Alpha Centauri. 100 years from now a starship should mass mere grams.

Meanwhile to forward the actual exploration of actual planets in this decade, here are a couple low-cost missions that would greatly increase our knowledge of hundreds of known planets and discover thousands of new planets respectively:

http://finesse.jpl.nasa.gov/

FINESSE would remotely characterize the chemicals on 200 planets: some of them presumably similar to planets in our own solar system, but dozens of them unique planets of a kind we’ve never studied before.

http://ntrs.nasa.gov/search.jsp?R=20120011750

TESS would be a follow-up to Kepler optimized to work with the James Webb Space Telescope and other future planet imaging telescopes. In other words to discover thousands of planets around bright stars which would make the best targets for JWST etc. to image and do even more in-depth remote (spectroscopic) chemical analysis.

By comparison traditional planetary science is becoming a sideshow. There is now far more to be learned from the thousands of just discovered and soon to be discovered planets.

[*] The Omniscient Prophets of our new Space Planning Directorate excepted of course!