I’ve been putting the finishing touches on a review article covering extrasolar planets that will be posted to arXiv in a few days. The list of to-do’s involves updating the figures, including the one shown just below, which charts \(M\sin i\)‘s of the RV-sourced planets in dark gray and simple radius-derived mass estimates of the transit-sourced planets in red. The steady Moore’s Law-like progression toward ever-lower masses has definitively reached Earth-mass (not to be confused with Earth-like) planets. The process took up only two decades, and was among the more impressive scientific advances of the recent past.
Here’s an elaboration of the above figure that doesn’t make it into the article, but is interesting nonetheless. On the y-axis is \(K/rms\), which is reasonably well correlated with the signal strength of Doppler velocity discoveries. One can certainly detect planets with confidence at low \(K/rms\), but it requires a large number of independent Doppler velocity measurements. The color corresponds to “astrobiological interest” — surely naive, and probably misplaced, but nonetheless quantifiable by my planet valuation formula.