Astronomers uncover a rare stellar trio with a Sun-like companion

Astronomers have confirmed a rare stellar trio: a rapidly spinning pulsar, a white dwarf and a Sun-like star orbiting them both. It is only the second confirmed three-star system known to contain a pulsar.

China’s FAST radio telescope first detected the pulsar, J0435+3233, in 2020. A pulsar is the remnant of an exploded star, sending out regular signals like a lighthouse. Five years of monitoring revealed that it and a white dwarf, another stellar remnant, orbit each other every eight days. But the time between its pulses was increasing unusually quickly.

A team led by Han Jinlin of the Chinese Academy of Sciences combined FAST observations with international optical, infrared and gamma-ray data. They identified a third star, with almost the Sun’s mass, orbiting the pair every 73.5 years. Its gravitational pull explains the unusual change in the pulsar’s measured timing.

The researchers infer that all three formed from the same cloud, but evolved at different rates. Unlike the previously known pulsar triple, which contains two white dwarfs, this system still has a Sun-like star rather than only stellar remnants.

A European team independently reached the same conclusion using similar archival data. Published on 9 October in The Astrophysical Journal Letters, the research provides a rare opportunity to investigate how triple-star systems evolve and to test theories of gravity.