Finding the next doomed worlds

Overview

Ultra-hot Jupiters (UHJs), defined here as giant planets with orbital periods under 2 days, are so large that tidal effects play a critical role in their formation and long-term dynamical stability. The population of hot-Jupiter host stars is younger than the general population of either field stars or planet-hosting stars, suggesting that many giant, close-in planets quickly inspiral or are otherwise destroyed. One UHJ, WASP-12 b, has been observed to have a decreasing orbital period, corresponding to a remaining lifetime of 3 Myr and a stellar tidal dissipation parameter Q_*’ = 1.8 x 10^5 However, even relatively rapid decay such as WASP-12 b demonstrates takes many years (10+) to observe, requiring observations over a long time span and across many instruments. UHJs are also relatively rare among planets, and the possible range of tidal dissipation parameters is unknown, making it hard to predict which particular UHJs might be decaying on human observable time scales. This proposal will observe 400+ transits of 38 UHJs over four years to provide a population of precisely timed objects, and will reveal how close to the brink these doomed worlds are.

Methodology

We will observe 38 UHJs using three sites in the northern and southern hemisphere, using mostly moderate-aperture, roboticized telescopes to acquire hundreds of transits with midtimes accurate to 1-2 minutes. We will update the transit ephemerides, so that future transits may be more accurately predicted. Combining four years of new data with literature data will give most of our target UHJs 10+ years of observations, which we will search for deviations from constant periods. If WASP-12 b is typical, we would expect some of the population we observe to have detectable orbital decay during the course of this proposal. If none is detected, than we can place constraints on the allowed $Q_star^prime$ value, providing the first empirical estimate of this fundamental property for a broad range of stars hosting UHJs.

Significance

We will monitor a population of bright (V<13), deep (>0.9%), transiting ultra-hot-Jupiters for deviations from constant period. This population is extremely valuable for many future research projects, including (but not limited to): high-precision atmospheric observations, possibly of escaping atmospheres, with JWST and other telescopes; theoretical modeling of how Q_*’ varies with planetary and stellar properties; and investigations into the formation and evolution of systems with giant, close-in planets.