After 90 years of research, scientists have discovered this mystery.
Previously, we knew that giant red stars are at the end stage of their evolutionary journey. They have diameters hundreds of times that of our Sun. And because the hydrogen supply in their core has been depleted, giant red stars have transitioned to hydrogen fusion in their outer shells. What’s inside these stars? This mystery has recently begun to unfold.
A group of astronomers from various countries has, for the first time, explained what is happening inside a giant red star. After observing the surface of dozens of giant red stars, they discovered extremely strong magnetic field objects hidden within.
Of course, no spacecraft can enter the core of a star. The technique that scientists use is called “asteroseismology.” Specifically, they exploit wave data on the star’s surface to explain what is happening deeper inside. This can be understood simply as performing a medical ultrasound.
However, the two types of waves that scientists are interested in are pressure waves from the star’s interior instability. These waves are similar to normal sound waves. The second type that can be used is gravitational waves generated by the buoyancy of different layers within the star. All the data extracted from these two types of waves are used to reconstruct what is inside a giant red star.
Giant red stars (GRBs) were chosen as the main research objects. They are all in the final stages of evolution. Because the hydrogen fusion process in the outer shell by nuclear reactions causes them to “swell” rapidly. They have a thin, puffed-up atmosphere, a dense helium core, and a radius hundreds of times larger than the original star.
This makes them excellent candidates for the “asteroseismology” technique. Their pressure waves do not escape from the core, but they are converted into gravitational waves. These waves pass through each layer inside the star and cause oscillations in different patterns. One of the relatively special patterns makes one side of the star brighter, while the rest becomes dimmer, known as a binary bright-dark pattern.
The research team found that a strong magnetic field inside the star is the reason why gravitational waves get trapped. They call it the “magnetic greenhouse effect.” This makes the binary bright-dark phenomenon of the star less pronounced.
Taking note of this, NASA used the Kepler space telescope to observe the binary bright-dark phenomenon of some giant red stars. Combined with data from the research team, they calculated that the “magnetic greenhouse effect” is holding a magnetic field inside the giant red star that is more than 10 million times stronger than Earth’s magnetic field. Dr. Jim Fuller, the lead researcher, said, “This is the first time we have been able to detect and measure the magnetic field inside a star. This discovery will help us understand more about the life cycle of a star.”
The discovery of the magnetic field inside the core of a giant red star is a remarkable achievement. Dr. Matteo Cantiello, co-author of the study, said, “In 1926, renowned astronomer Sir Arthur Eddington lamented that the core of a star is the most inaccessible thing in the universe. Nearly 90 years later, and we’ve done it. If Eddington were here today, he would probably be very surprised and delighted.”