A diamond planet around a pulsar

PSR J1719-1438 is a pulsar with a rotation period of 5.8 milliseconds, 4000 light-years away from the Earth, visible in the constellation Serpens.

Timing measurements showed the presence of an exoplanet in orbit around it.

The planet completes a revolution in just two hours and 10 minutes and orbits at a distance of 600,000 km, less than a solar ray. Its mass is slightly higher than that of Jupiter, but its radius is 40% than the Jovian one. This means that the density of the planet is very high: it should therefore be composed mostly of carbon. This means that PSR J1719-1438b has a structure that is very similar to that of the diamond!

The planet actually is nothing but the remnant of a very massive star whose gas has been torn away by the pulsar during the process which accelerated it up to its current rotation speed.

Credit: NASA/JPL-CALTECH/R. HURT (SSC).