The US-British team of astronomers has discovered that the exoplanet WASP-12b could have ultra-rich concentrations of carbon and that the core of the planet may consist of pure diamond. The research team of the Taurus Hill Observatory has also observed this exoplanet WASP-12b. The latest successful transit observation was made 4.1.2009. The light curve is below.

Observers: Veli-Pekka Hentunen and Markku Nissinen.

More about the "Diamond planet":

YLE - "Taivaalta löytyi "timanttiplaneetta" (in Finnish)
BBC - "'Diamond exoplanet' idea boosted by telescope find" (in English)