Astronomers found a real “Three-Body” star system 7,000 light-years away

Two dead stars and one living star are circling each other about 7,000 light-years from Earth, and Chinese astronomers have now mapped how. The trio, named PSR J0435+3233, looks a bit like the setup in Liu Cixin’s famous novel The Three-Body Problem. It behaves very differently, though, and that is exactly why scientists find it so valuable.

A radio telescope the size of a small valley

The discovery came from FAST, the Five-hundred-meter Aperture Spherical radio Telescope in southwestern China. It is the world’s biggest single-dish radio telescope. According to People’s Daily, the pulsar was first detected on 8 June 2020, and the team then spent about five years watching it closely. A pulsar is the leftover core of a star that exploded. It is tiny and extremely dense, and it sends out beams of radio waves that sweep past Earth like a lighthouse.

This pulsar spins once every 3.2 milliseconds, which works out to more than 300 turns every second. The South China Morning Post compares that to the blades of a kitchen blender. Because those pulses arrive with clock-like precision, even tiny delays reveal that something is tugging on the pulsar.

Two orbits, nested like a set of dolls

The timing delays showed two separate orbits. In the inner one, the pulsar circles a helium white dwarf, another dead star, once every eight days. In the outer one, a Sun-like star travels around that tight pair once every 73.5 years on a stretched, oval path.

The team, led by Z. L. Yang with J. L. Han as corresponding author, combined radio and gamma-ray timing with archival optical and infrared data and with positions from the Gaia space telescope. The paper in The Astrophysical Journal Letters puts the system about 2.1 kiloparsecs away, which is roughly 6,800 light-years, with a fairly wide margin of error. The distant star is a G-type subgiant with a mass close to that of the Sun.

Why it is not quite the Three-Body Problem

In physics, the three-body problem describes three objects of similar weight pulling on each other in a chaotic dance that has no tidy solution. The pulsar system is calmer. A tight inner pair and a far-off third star form what astronomers call a hierarchical triple, and that arrangement stays stable and predictable. The fiction and the real star system share a name, but not much else.

A rare survivor

Pulsars form when massive stars explode as supernovae, and that blast can easily hurl companions away. Triple systems that include a fast-spinning pulsar are therefore extremely rare. People’s Daily reports that the only earlier example came from the Green Bank Telescope in the United States and holds one pulsar and two white dwarfs, which would make this the second known. The authors suggest the three stars may have been born together from the same gas cloud and stayed bound to each other.

The pulsar also shows an odd drift. Its spin period grows by about one nanosecond per year, which Chinese media say is roughly 100 times faster than in comparable pulsars. The third star’s pull may help explain that.

What happens in 2036

The paper’s fit puts the outer star’s closest approach in about April 2036. That gives astronomers a scheduled test. Chinese state media say the system could serve as a natural laboratory for probing the strong equivalence principle, an idea in Einstein’s gravity theory which says that gravity should pull on objects the same way regardless of what they are made of. A neutron star is a very different object from a white dwarf, so watching both fall toward a third star can push that idea harder than any lab on Earth.

Caveats and open questions

The masses of the three stars are not pinned down yet. The paper offers two workable orbital geometries, one almost perpendicular to the inner orbit and one moderately tilted, and each gives different masses. The 2036 flyby should help choose between them. The authors also expect the system to end up as a neutron star with two white dwarfs as the Sun-like star ages. The claim that this is only the second such system comes from news reports rather than the paper’s abstract, so it may change if other teams find more.

For now, one thing is clear: a patient decade of radio listening has turned a lone flickering pulsar into a three-star story, and the next chapter arrives in 2036.

Sources

• Yang, Han et al., The PSR J0435+3233 Triple System (arXiv:2608.01227, accepted by The Astrophysical Journal Letters)
• People’s Daily: China’s FAST telescope identifies pulsar as part of evolving primordial triple star system
• CGTN: China’s FAST telescope finds rare triple star system still evolving
• South China Morning Post: Chinese astronomers find real 3-body system