China FAST Telescope Identifies Evolving Primordial Pulsar Triple System

Xinhua News Agency reported that Chinese researchers combined radio observation data from China's FAST telescope with international optical and gamma-ray multi-band astronomical data to reveal pulsar J0435+3233 as the first primordial triple system still in an evolutionary stage, making it the second confirmed pulsar triple system. Pulsar J0435+3233 was first observed through FAST on June 8, 2020, by the National Astronomical Observatories drift scan survey team with a rotation period of 3.2 milliseconds, after which follow-up monitoring by the Xinjiang Astronomical Observatory team across five years obtained 192 measurement results. FAST data analysis indicated that the pulsar and a white dwarf orbit a common center of mass in a circular orbit every 8 days, while the pulsar period increases by 1 nanosecond each year. A team led by Han Jinlin of the National Astronomical Observatories analyzed open archival radio, infrared, and optical data alongside 160 valid gamma-ray photons accumulated over 18 years by the Fermi satellite, locking in the optical companion and verifying the triple system. The second companion is an evolving sun-like star with nearly the same mass as the Sun, which orbits the binary system every 73.5 years with an eccentricity of 0.6, causing the previously measured abnormal increase in the pulsar rotation period. The discovery reflects multi-band data fusion and relay exploration by domestic and international research teams, with findings published on October 9, 2026, Beijing time in The Astrophysical Journal Letters.

According to stellar evolution theory, after long evolution the sun-like companion star will eventually extinguish, transforming this setup into a long-term stable triple system composed of one pulsar and two white dwarfs.