With news of new extrasolar planets being released nearly weekly, there is a general feeling that we are in the midst of a singular moment in cosmic discovery. And the news a few weeks ago of a planet that is about the same size as Earth has provided the sense that the discovery of a planet truly similar to Earth – one that could actually sustain life – is on the horizon.
But can we actually predict when the first Earth-like planet will be discovered? In a forthcoming paper in PLoS ONE (to be published October 4th), Greg Laughlin and I attempted to do this. This paper, A Scientometric Prediction of the Discovery of the First Potentially Habitable Planet with a Mass Similar to Earth, uses the properties of previously discovered exoplanets, including the year of their discovery, to estimate when the likeliest time of this potentially habitable planet will be discovered. (Greg writes about our paper here).
Spoiler: early to mid-2011.
Of course, it’s a bit more complicated than that, but here’s an overview of what we did. Using the properties of previously discovered exoplanets, we developed a simple metric of habitability for each planet that uses its mass and temperature to rate it on a scale of 0 to 1, where 1 is Earth-like, and 0 is so very not Earth-like. Plotting these values over time and taking the upper envelope yields a nice march towards habitability.
Using a simple bootstrap sampling analysis, we calculated when a logistic curve fit to such an upper envelope would get to a habitability of approximately 1. And the likeliest time is early to mid-2011, or more precisely, early May 2011. Of course, there are precision considerations, but we are heartened by recognizing that our method shows a 75% chance of such an announcement by the end of 2013 (which is when many astronomers predict such a discovery), and that February 2011 is when we are due for a large release of data and announcement by NASA’s Kepler mission. Our method, using only previous discoveries, accords well with such informed estimates.
Now, we wait and see how close our prediction actually is to reality.
Samuel Arbesman, & Gregory Laughlin (2010). A Scientometric Prediction of the Discovery of the First Potentially Habitable Planet with a Mass Similar to Earth PLoS ONE (in press) arXiv: 1009.2212v1