Astronomers have discovered for the first time a rapidly orbiting neutron star paired with a helium companion star. This discovery sheds light on a rare common shell evolution process, a theoretical mechanism for the formation of binary systems that has remained poorly understood until now. The results of the study are published in the journal Science.
Unusual pair
Most stars in the Universe exist in binary systems. But the discovered duo has an anomaly. A millisecond pulsar (a neutron star spinning at hundreds of revolutions per second) is associated with a helium companion that has lost its outer layers. Such systems were considered possible in theory, but they had never been observed before.
The discovery was made thanks to China’s FAST radio telescope. In 2020, a team led by Jin Ling Han detected faint radio signals from the depths of the Milky Way. Four years of observations have confirmed: this star is not alone. Inside its outer layers was a pulsar, which formed a very compact binary system. With an orbital period of only 3.6 hours, this pulsar and its companion orbit very closely around each other.
Needle in a haystack
Typically, millisecond pulsars are formed by “sucking” matter from ordinary neighboring stars. In this case, however, the process had a different scenario. The helium companion was once a star that expanded enough to swallow the pulsar. Under the action of gravity, the outer hydrogen layers of the companion dissipated, leaving only a dense helium core gravitationally bound to the neutron star.
“It’s like cosmic braking,” explains Duncan Lorimer, an astronomer from West Virginia. “The companion loses mass and the pulsar accelerates its rotation, forming a superdense system.”
Such a mechanism, known as “common shell evolution,” has been hypothesized for decades but has only now received direct evidence. Such systems account for only 0.1% among millisecond pulsars. Scientists suggest that there may be about a dozen more such systems in the Milky Way.
“It’s like finding a needle in a haystack,” comments Victoria Kaspi of McGill University. “But findings like this help rewrite our ideas about the life cycles of stars.”
Quantum interaction
Han’s team plans to continue monitoring the system to understand how the helium companion interacts with the pulsar at the quantum level. Data from FAST and other telescopes are expected to reveal new details about the thermodynamics of such pairs.
“Each such system is a unique laboratory for studying extreme physical conditions,” Han emphasizes. The discovery is a reminder: even in our galaxy, there remain many mysteries that leave space for scientific sensations.
Previously, we explained the arrangement of X-ray binary stars.
According to Sci News
