A Young White Dwarf Companion to Pulsar B1620-26: Evidence for Early Planet Formation

The pulsar B1620-26 has two companions, one of stellar mass and one of planetary mass. We detected the stellar companion with the use of Hubble Space Telescope observations. The color and magnitude of the stellar companion indicate that it is an undermassive white dwarf ($0.34 \pm 0.04$solar mass) of age$480 \times 10^6 \pm 140 \times 10^6$years. This places a constraint on the recent history of this triple system and supports a scenario in which the current configuration arose through a dynamical exchange interaction in the cluster core. This implies that planets may be relatively common in low-metallicity globular clusters and that planet formation is more widespread and has happened earlier than previously believed.