Astounding Discovery: Scientists Uncover Unique Double-Star System with One Star Orbiting Inside the Other!

Astronomers have made a fascinating discovery: a rare binary star system where one star actually used to orbit inside its partner. The focus of this study is a pulsar called PSR J1928+1815, located about 455 light-years from Earth. A pulsar is a neutron star, a remnant of a massive star that exploded in a supernova. These stars are incredibly dense, primarily made up of neutrons, the result of protons and electrons being crushed together by intense gravity.

Pulsars spin rapidly, sending beams of radio waves from their magnetic poles. We only see the pulse when one of these beams points toward Earth, kind of like a cosmic lighthouse. Researchers believe this pulsar formed from a hot blue star more than eight times the mass of our sun.

Using the Five-hundred-meter Aperture Spherical Radio Telescope (FAST) in China—a gigantic telescope—the team discovered that PSR J1928+1815 has a companion star. This companion is a helium star, which has lost most of its hydrogen layers, leaving behind a helium core. The two stars are quite close, about 700,000 miles apart—around 50 times closer than Mercury is to the sun—and they orbit each other every 3.6 hours.

PSR J1928+1815 is classified as a millisecond pulsar, spinning nearly 100 times a second. This speed often occurs because pulsars pull in material from neighboring stars, speeding up their rotation. Previous studies suggested that such pulsar-binary systems may go through a “common envelope” phase, where the pulsar resides within the outer layers of its companion. However, this is the first time scientists have identified such a system.

Researchers modeled the system’s formation, positing that the stars began about 185 million miles apart. Over time, the pulsar began to pull away the outer layers of its companion, forming a shared envelope around both stars. After roughly 1,000 years, the pulsar moved closer to the core of its companion, shedding the remaining envelope and creating a stable binary system.

Statistically, only about 16 to 84 similar systems like PSR J1928+1815 might exist in our Milky Way. For context, our galaxy contains around 100 billion to 400 billion stars. The findings were detailed in the journal Science on May 22, 2023. This discovery not only sheds light on star formation but also helps us understand the complex dynamics of binary star systems better.

Experts emphasize the importance of these findings. Dr. Jin-Lan Han, a prominent figure in the research, notes that this discovery could inform future studies on stellar evolution and the life cycles of binary systems. As we explore the universe, revelations like these offer a window into the forces shaping our cosmos.

To read more about this discovery, check out the full study in Science.

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