Astronomers have discovered a rare binary star system, designated PSR J1928+1815, located 455 light-years away. This system features a millisecond pulsar orbiting a helium star, offering unprecedented insights into stellar evolution.
Observations made with China's Five-hundred-meter Aperture Spherical radio Telescope (FAST) revealed that the pulsar spins rapidly, completing a rotation every 10.55 milliseconds. The pulsar and its companion star orbit each other in a tight 3.6-hour orbit, separated by only 1.12 million kilometers—approximately 50 times closer than Mercury is to the Sun.
The system is believed to have formed through a "common envelope" phase, where the pulsar spiraled inside the companion star, causing the ejection of the outer layers and leaving behind a helium core. This discovery, reported in the journal *Science* on May 22, 2025, supports theoretical models of binary star evolution and suggests that 16 to 84 similar systems may exist in the Milky Way.