Weather Detected

An exoplanet reflects and emits light as it orbits its host star, thus forming a distinctive phase curve. By observing this light, we can study the atmosphere and surface of distant planets. post post

Example flux maps of the planetary dayside and their thermal emission (red), reflected flux (blue) and total (magenta) phase curve components.

The planets in our Solar System show a wide range of atmospheric phenomena, including stable wind patterns, changing storms and evolving anomalies.

HAT-P-7 b is an exoplanet with brightness varying in offset from its orbit which implies that the peak brightness repeatedly shifts from one side of the planet’s substellar point to the other. The variability occurs on a timescale of tens to hundreds of days.

These shifts in brightness are indicative of variability in the planet’s atmosphere, and result from a changing balance of thermal emission and reflected flux from the planet’s dayside. We suggest that variation in wind speed in the planetary atmosphere, leading to variable cloud coverage on the dayside and a changing energy balance, is capable of explaining the observed variation.


I find it interesting that these results varying on a timescale of tens to hundreds of days have been extracted from four years of previously reported observations through extremely careful data analysis. The weak signal can be separated from that of the bright star by relying on the known orbital period of 2.2 days.

In radio terms the orbital period provides a carrier wave for the weak signal. I'm reminded of the clever placement of carrier signals to coax existing wireless networking equipment to hear Low Power WiFi.

Similarly advanced signal processing provides for the Exquisite Sensitivity of the LIGO interferometers detecting gravitational waves.