Chinese astronomers discover rare compact binary system of pulsar, helium star

China

Chinese astronomers discover rare compact binary system of pulsar, helium star

2025-05-23 11:30 Last Updated At：16:17

Chinese astronomers have discovered a rare compact binary system consisting of a millisecond pulsar and a companion helium star formed by common envelope evolution, which sheds light on future research on stellar evolution theory.

The research, conducted by a team led by professor Han Jinlin from the National Astronomical Observatories of the Chinese Academy of Sciences using China's Five-hundred-meter Aperture Spherical Radio Telescope (FAST), was published on Science online on Thursday.

Pulsars are spinning neutron stars that originate from the imploded cores of massive dying stars through supernova explosions. They emit twin beams of radio waves from their magnetic poles. These beams appear to pulse because astronomers see them only when a pulsar pole is pointed at Earth.

Thanks to the high sensitivity and detection abilities of FAST, the Chinese team identified a pulsar with a spin period of 10.55 milliseconds in a compact binary system, which has an orbit radius of 500,000 kilometers and an orbital period of 3.60 hours.

The companion star has 1.0 to 1.6 solar masses, eclipses the pulsar for about 17 percent of the orbit, and is undetected at other wavelengths, so it is most likely a stripped helium star.

The scientists interpret this system as having recently undergone a common envelope phase, thus producing a compact binary.

Such binary systems are very rare and hard to detect, because they only exist for about 10 million years. The team estimates only dozens of other examples of this system may exist in the entire galaxy.

This discovery is of great significance to the study of stellar evolution, physics of accretion onto compact stars, and gravitational-wave sources from mergers of binary stars.

FAST, the world's largest filled-aperture and most sensitive radio telescope, is located in a naturally deep and round karst depression in southwest China's Guizhou Province. It started formal operations in January 2020 and was officially opened to the world in March 2021.

Japanese official criticizes Takaichi's erroneous remarks

The series of erroneous words and actions by Japanese Prime Minister Sanae Takaichi not only seriously deviate from the spirit of pacifist Constitution of the country but also further exacerbate regional tensions, said Tomoko Tamura, a member of the House of Representatives.

In an exclusive interview with China Central Television (CCTV), Tamura criticized Takaichi for straining Japan-China relations by making erroneous remarks on Taiwan, calling on her to improve bilateral relations.

Tamura pointed out that the political consensus reached during the normalization of diplomatic relations between the two countries remains of great significance, and Japan should respect and abide by it as the basis for repairing and rebuilding friendly relations with China.

"The erroneous remarks by Sanae Takaichi this time have led to the deterioration of China-Japan relations. This is absolutely unacceptable and must be retracted. Regarding the relations between two sides, the consensus reached during the normalization of diplomatic relations in 1972 is of utmost importance. At that time, the Chinese government asserted that Taiwan is part of China and the Japanese government fully understood and respected this stance. Now we should reaffirm this consensus, as well as the crucial agreements reached by both countries after 1972. Japan should explicitly acknowledge these significant agreements to rebuild friendly relations with China," she said.

Tamura also pointed out that in recent years, Japan has attempted to reshape its security policy, boosting defense spending, easing arms-export restrictions, pursuing offensive weapons development, and clearly deviating from the fundamental principle of "exclusively defense-oriented" policy.

"Japan's possession of long-range missiles clearly exceeded the scope of 'exclusively defense-oriented' policies. Japan is accelerating its military expansion. From the perspective of the Japanese constitution, this is absolutely not allowed. We are deeply concerned about the current Takaichi administration's disregard for the Japanese constitution. We clearly demand that Japan should adhere to the position of resolving issues through diplomatic efforts," she said.