Rare ‘Cannibal’ Star System Discovered: Pulsar Devours Helium Star in Tight Orbit
In a groundbreaking discovery, astronomers have identified a rare binary star system featuring a millisecond pulsar locked in a tight orbit with a helium star. This system, dubbed PSR J1928+1815, offers unprecedented insights into the final stages of stellar evolution and the dramatic interactions between stars in close proximity.
The research, published in the journal Science, details how a team of scientists in China used the Five-hundred-meter Aperture Spherical radio Telescope (FAST) to observe this fascinating celestial dance. What makes this system unique is the incredibly close proximity of the two stars, orbiting each other in a mere 3.6 hours. They are approximately 50 times closer than Mercury is to the Sun.
The pulsar, a rapidly spinning neutron star, is rapidly spinning, nearly 100 times a second. Millisecond pulsars gain such incredible speed as they siphon material from nearby companions. Previous models suggested that such interactions can lead to a "common envelope" phase, where one star essentially orbits within the outer layers of the other. This new observation seems to confirm that theory.
"Researchers on the team first spotted the pulsar back in May of 2020", explains lead researcher Dr. ZongLin Yang. "and soon thereafter noticed that not only did it spin incredibly fast, but for one-sixth of its orbit, its radiation emissions were blocked. That suggested an object was passing between it and Earth."
The team believes the helium star companion was once a larger star with a hydrogen envelope. Over time, the pulsar's intense gravitational pull stripped away the hydrogen, leaving behind a core primarily made up of helium. This process explains the system's compact nature and provides valuable information about mass transfer in binary systems.
The implications of this discovery are significant. Scientists estimate that only 16 to 84 similar systems may exist in the entire Milky Way galaxy. Finding and studying these rare examples is crucial for understanding the evolution of binary stars and the formation of exotic objects like millisecond pulsars.
This newfound system likely spent roughly 1,000 years in the common envelope phase. According to Han Jin-Lan, chair of the radio astronomy division, The pulsar would have then started siphoning off its companion's outer layers, forming a common envelope around them both. After this phase the tightly bound binary system was left behind.
The discovery raises important questions about stellar evolution and the dynamics of binary systems. What other hidden gems are lurking in our galaxy, waiting to be discovered? Share your thoughts and theories in the comments below!
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