How close are we to having the technology to measure planetary obliquity for exoplanets?
Carter &amp; Winn (2010) suggest that the most promising means of detecting exoplanet obliquity would be through miniscule signatures imprinted on the transit light signal at ingress and egress (~ 200 parts per million for a planet as oblate as Saturn). Zhu et al. (2014) use this technique to make the first tentative detection of exoplanet obliquity from a Kepler object, the 18 Jupiter mass brown dwarf Kepler 39b (KOI-423.01). They measure an oblateness of 0.22±0.11. They also place some upper constraints on the oblateness of other planets in the Kepler catalogue.


Transit signal for KOI-423.01 over 12 orbits. The residuals of two models, one with oblateness and one without, are plotted at bottom. The Oblateness model is a better fit to the data.

Oblateness variations are thought to be conducive to exoplanet habitability by regulating temperature modulations, so I expect that measurements of this property over time will be a priority in future exoplanet observations for astrobiology and SETI studies.