Institute for Advanced Study / Princeton University Joint Astrophysics Colloquium

Modern astronomical spectrometers are approaching the exquisite sensitivity to detect the signature of an Earth-mass planet around stars like the Sun. I shall discuss the challenges involved in making these difficult measurements with the Doppler radial velocity technique, and the evolution of the design of these instruments as they seek ever-tighter control of environmental parameters, and increased measurement precision. A suite of new technologies like frequency stabilized laser combs, low drift etalons, and deeper understanding of the detectors is enabling a new level of precision in radial velocity measurements - as well as illustrating new challenges.  I will use two such instruments we have built to illustrate some of the underlying physics and measurement challenges.  I will then discuss how the stars themselves are the remaining challenge, as magnetically driven processes create ‘stellar activity’ noise that can masquerade as planets and obfuscate their detection. I shall highlight a few paths we are exploring to mitigate this – using our star, the Sun, as a guide, and discuss whether the goal of discovering and characterizing terrestrial mass planets capable of hosting liquid water on their surfaces is now within reach.