The year 2016 barely began when the claim was made that there is evidence for a yet undiscovered planet (Planet 9) within our solar system. You would think that nothing could stir more the astronomy community and the general public…. But here comes the direct detection of gravitational waves and the excitement reaches new heights… No question, for astronomy the year 2016 is off to an extraordinary start!
While you might not be surprised to read about Planet 9 in this column (see also “Focus on Planet 9“), you might wonder why I mentioned gravitational waves. Obviously, because their direct detection is a monumental milestone in physics and astronomy and a dramatic confirmation of the theory of general relativity proposed by Albert Einstein in 1916. But not only…
By essence, astronomy is an observational science and so theoretical predictions of this calibre are intrinsically rare. Nevertheless, for planetary scientists another extraordinary example springs to mind. The existence of Neptune was deduced from the analysis of small perturbations in the orbit of Uranus by Urbain Le Verrier and John Couch Adams in 1845! Shortly thereafter, the astronomer Johann Gottfried Galle discovered the planet within less than one degree of the predicted position. Another dramatic observational confirmation of Newton’s theory of gravitation published a century and a half before.
With Newtonian gravity and general relativity well established, the detection of the putative Planet 9 will not really come as the observational confirmation of some fundamental laws of physics. It rather will have to be considered as a dramatic demonstration of the power of the existing laws, cutting edge astronomical observations, and sound reasoning.
While everyone is eagerly waiting for a detection, this claim shows that exploring the solar system is far from boring and that the potential for enormous surprises is still there. It also shows the added value of combining theory and observations which is precisely what PlanetS is all about.
Director NCCR PlanetS