Latest news with #NationalAstronomicalObservatories
Yahoo
3 days ago
- General
- Yahoo
Scientists Startled by Discovery of Small Star Swimming Through Outer Layers of Another Larger Star
A team of researchers in China have discovered a stunning binary system in which a stellar object known as a pulsar orbited inside the outer layers of its companion star — which it accomplished after stripping its host's innards and dispersing them into space. The findings, detailed in a new study published in the journal Science, are an incredibly rare example of a "spider star" that preys on its companion, so-named because of the female arachnids that devour males after mating. And tantalizingly, the grisly scene is some of the best evidence yet of a stage of stellar evolution called the common envelope phase, which has never been directly observed by astronomers. Pulsars are rapidly spinning neutron stars, the incredibly dense stellar cores that are left over in the aftermath of a supernova. Everything about neutron stars exhaust superlatives — their gravity most of all. They are so tightly packed, containing more mass than our Sun inside a form just a dozen miles in radius, that all their atoms and their constituent protons and electrons have been crushed into neutrons, with just a teaspoon of this improbable matter weighing trillions of pounds. Their powerful magnetic fields, billions of times stronger than Earth's, unleash beams of radio waves into space along their poles. Further beggaring belief, some neutron stars become pulsars, which spin up to hundreds of times per second after siphoning material from a stellar companion, if it has one. Their sweeping beams of radiation, like cosmic lighthouses, look like a repeating signal to observers. The newly discovered pulsar, PSR J1928+1815, intrigued the astronomers because its radio pulses suggested that it was extremely close to its host, completing an orbit every 3.6 hours. They also noticed that for one-sixth of that orbit, the pulsar would vanish from view, indicating that the host was eclipsing it. "That's a large part of the orbit," coauthor Jin-Lin Han, a radio astronomer at the National Astronomical Observatories in Beijing, told Gizmodo. "That's strange, only a larger companion can do this." Over four and a half years, Han's team closely observed the system using the Five-hundred-meter Aperture Spherical Radio Telescope (FAST) in southern China, the largest and most powerful single-dish radio telescope in the world. Their observations revealed that the host star was between one to 1.6 times the mass of our Sun, while the pulsar was more likely 1.4 stellar masses. Determining the make of the host star, however, took some additional sleuthing. Its tight orbit and the fact that it was only detectable in radio wavelengths, Giz noted, ruled out its being a Sun-like star. And since it was large enough to eclipse the pulsar, it had to be something larger than a stellar remnant like another neutron star. That pointed to something altogether more spectacular: a helium star, created after the pulsar, when it was still an ordinary neutron star, tore off its host's layers and created a huge common envelope, a cloud of hydrogen gas that swallows both the stars. In this case, the poor star under attack managed to cling on to its evacuated innards for just 1,000 years — a blink in a stellar lifespan — before the whole, mighty envelope fell apart. Fleeting as it was, its impact is lasting: the friction exerted by the gases gradually nudged both stars closer together. Common envelopes are rare because the process of a neutron star stripping its companion, which causes it to spin and graduate to a pulsar, usually results in all the siphoned material being devoured. But if the companion is massive enough, much of it survives. The discovery marks the first spider star found orbiting a helium star. While the astronomers didn't get to witness the envelope in action, this is some of the most convincing evidence to date that this long-theorized stage of stellar evolution exists. In all, the team estimates that there're just 16 to 84 star systems like this one in the entire Milky Way — and, against all odds, we got to see one. More on space: Scientists Puzzled by Mysterious Motion in Atmosphere of Saturn's Moon
Gizmodo
22-05-2025
- Science
- Gizmodo
One Star Is Orbiting Inside Another in This Never-Before-Seen Binary System
For the first time, astronomers have spotted a rapidly spinning neutron star that is gravitationally bound to a helium star companion. The discovery of this unusual binary system helps confirm a long theorized—but rarely seen—cosmic process called common envelope evolution. Binary star systems, or pairs of stars that orbit around each other, are very common. In fact, it's estimated that 85% of stars in the universe have at least one companion. But this newly discovered pair is unlike any seen before. In this case, a helium star is bound to a millisecond pulsar: a fast-spinning neutron star that emits beams of radiation at regular intervals. These stars achieve their extraordinary rotation rates by siphoning matter from nearby stellar companions. In May 2020, a team of researchers led by Jin Lin Han, a radio astronomer at the National Astronomical Observatories and the Chinese Academy of Sciences in Beijing, used China's FAST radio telescope to detect weak signals from a point deep within the Milky Way galaxy. A few months later, the researchers confirmed that these signals were radiation emissions from a pulsar. They then tracked these bursts for four and a half years, and their measurements revealed that this star isn't alone. It's actually part of a binary system, orbiting its companion every 3.6 hours. But for one-sixth of that orbit, the pulsar's radiation is blocked—or eclipsed—by its companion. 'That's a large part of the orbit,' Han told Gizmodo. 'That's strange, only a larger companion can do this.' In binary systems, a millisecond pulsar is usually accompanied by a white dwarf: a hot, dense core left behind after a star like our Sun has exhausted its fuel. But the data Han and his colleagues collected indicated that this companion had to lie somewhere in between a compact object and a normal star, he said. Further investigation of this strange companion revealed that it is roughly as massive as our Sun, but it couldn't be a normal star because it was undetectable in all wavelengths outside of the radio spectrum. This led the researchers to conclude that it's a star stripped clean of its hydrogen, leaving behind a core primarily composed of helium. They published their findings today in the journal Science. This type of binary system 'has never been discovered before,' Han said. But it has long been theorized that such a pairing could form via common envelope evolution, and he and his colleagues believe that's what happened here. 'The process of common envelope evolution is slightly different to how stars like pulsars are often thought to interact in binary systems,' Duncan Lorimer, a professor of physics and astronomy at West Virginia University who was not involved in the study, told Gizmodo in an email. Normally, a neutron star's intense gravitational field pulls material from a companion star that has expanded, allowing its gaseous outer layers to be 'eaten' by the neutron star, he explained. This process, called accretion, causes the neutron star to 'spin up' and become a pulsar. But in common envelope evolution, 'the companion star is so large that its outer layers engulf the neutron star as well,' Lorimer said. 'This acts as a brake on the whole binary system.' Inside the companion star's outer layers—the envelope—friction causes the pulsar and the companion's core to spiral toward each other, forming a highly compact binary system, like the one Han and his colleagues have now observed. With an orbital period of just 3.6 hours, this pulsar and its companion are circling each other very closely. Ultimately, the outer layers of the companion star are expelled, Lorimer said, which explains why this millisecond pulsar's helium star companion has been stripped. 'The evolutionary pathway that the authors set out, it's not a surprising pathway,' Victoria Kaspi, a professor of physics at McGill University who was not involved in the study, told Gizmodo. 'It's one that has been recognized, identified, discussed in detail for many years.' 'The interesting question is, if you're going to find 1,000 millisecond pulsars, what fraction of them will be like this one? It's about one in 1,000—something like that. And they found it,' she said. Han and his colleagues believe there are more than a dozen other systems like this one in our galaxy, making them exceptionally rare. The fact that these researchers found one of them is a 'great breakthrough,' Lorimer said. 'The more millisecond pulsars we find, the more likely we are to find examples of rare evolutionary outcomes. This system is an excellent example of that,' he said.
South China Morning Post
05-05-2025
- Science
- South China Morning Post
Is ancient Chinese astronomer Shi Shen's stellar catalogue the world's first star log?
Two Chinese scientists believe their country's earliest star catalogue – an astronomical list of celestial bodies known as 'Shi's Star Catalogue' – is the world's oldest star log, dating back some 2,400 years. Advertisement Citing new evidence in a study published on April 4 in the peer-reviewed astronomy journal Research in Astronomy and Astrophysics, researchers Zhao Yongheng and He Boliang from the National Astronomical Observatories, under the Chinese Academy of Sciences, said that Shi's Star Catalogue was created around 335BC. That would make the stellar accounts , also known as the Star Manual of Master Shi, the oldest known human records of the stars, according to the study. In their investigation, the astronomers used image processing technology to convert ancient records into measurable celestial coordinates, which ultimately confirmed approximate years of observations in the main content of Shi's Star Catalogue, which was followed by supplementary revisions centuries later, around AD125. Experts believe that astronomers from both China and Greece began studying the night sky in detail at around the same time. Advertisement Until now, the Hipparchus star catalogue from Greece has been recognised as the world's oldest, believed to have been created in the 2nd century BC. But the new research published by Zhao and He suggests that the Chinese catalogue is the oldest known human record of the stars.
