This is an excerpt from my post on Astrobites:

Title:  Why Are Pulsar Planets Rare?
Authors: Rebecca G. Martin, Mario Livio, and Divya Palaniswamy
First Author’s Institution: University of Nevada
Status: Accepted in the Astrophysical Journal

Pulsar planets were the first type of planet ever discovered beyond the solar system, and it shocked the astronomical world.  These were not the planets we expected: solar system-like planets around a Sun-like star.  Instead, these planets orbited a pulsar, a rapidly rotating neutron star (the extremely dense core of a massive star that exploded as a supernova). However, since their initial discovery in 1992, only five such pulsar planets have been found, making them quite rare.  Fewer than 1% of pulsars have been found to host planets.  In this paper, the authors explore how these planets may have formed as a way to explain the rarity of pulsar planets.