What is magnetar?
If the mass of a star exceeds the mass of the sun by eight or more, then in the later stages of evolution, when almost all the fuel is used up, it turns into a supernova. If the mass of the residue after the explosion is large for a white dwarf (a type of star that glows due to its thermal energy) but small for a black hole formation, then a neutron star is formed. The radius of such objects is measured in tens of kilometers, but due to their extreme density, their mass is close to that of the sun. Matter familiar to humans on Earth cannot exist in such conditions, and so such stars contain exotic matter composed of pure neutrons, more densely compressed than an atomic nucleus.
Neutron stars can be very different, and some form magnetars. These are the strongest magnets in the universe with fields of the order of 10.eleven TL. For comparison, the fields of the strongest superconducting artificial magnets are measured in tens of Tesla. Because the nearest magnetar is so far from Earth, astronomers know very little about them. It is unclear, among other things, how and from what stars they were formed. At least, no stars are known to scientists that could transform into a magnetar.
False Wolf-Rayet
The binary star HD 45166 has been known to astronomers for over a hundred years, and all that time scientists could not understand its anomalous nature. 4 thousand sv is removed from the earth. It consists of a year and two components: an ordinary star with four solar masses and its strange companion. In terms of spectral characteristics, it resembles extremely bright and hot (up to 200,000 kelvin) Wolf-Rayet stars. This class includes massive stars in the final stages of their evolution that have consumed a significant portion of their hydrogen but are rich in helium.
But HD 45166 is different from other Wolf-Rayet stars. Radiation from any star can be decomposed into a spectrum using, for example, a prism, but other methods will be required for X-rays and radio range. The spectrum completely depends on the characteristics of the star, thanks to which you can find out its chemical composition and other parameters. That’s why astronomers say it contains a lot of oxygen, nitrogen, and carbon, and its mass is (and not dozens of times) that of the Sun.
With reveal Tomer Shenar of the University of Amsterdam and colleagues compared observation results using three optical telescopes: the 3.60-metre CFHT in Hawaii, the Chilean MPG/ESO, and the Mercator telescope in the Canary Islands.
The most magnetic star
An analysis of the star’s emission showed that some spectral lines of the anomalous component HD 45166 were strongly split due to the Zeeman effect. As a rough analogy, a prism can be thought of as separating light, but the observer sees separate stripes instead of a “rainbow” due to an unusual light source. Under the influence of a magnetic field, these strips can split into many small and thin ones, called the Zeeman effect.
As a result, the scientists were able to find that the anomalous component HD 45166 has a magnetic field of 4.3 Tesla. That’s not much by the standards of superconducting magnets (they cost 8.7 T at the Large Hadron Collider), but it’s an absolute record for “ordinary” stars (not neutron ones). Additionally, man-made magnets are small, and a star’s magnetic field has a high inductance over its entire field. It was also possible to clarify that the temperature of this star is 15 thousand kelvins less than previously thought, about 56 thousand kelvins, and its mass is equal to two suns.
All this makes it necessary to separate the anomalous star into a separate new species. “It’s very interesting to discover a new type of astronomical object, especially when it’s been hidden for so long,” explained Tomer Shenar.
The mystery of the origin of magnetars
Scientists have predicted what awaits the star in the future. Simulations have shown that it will eventually shrink and turn into a neutron star. The surface area will decrease many times, resulting in an increase in the magnetic field due to the law of conservation of magnetic flux. If the radius equals 12 km, the inductance of the magnetic field will reach 10 lb.10 Tl lb – just such a field is observed in magnetars.
So where did such a strange star of the Wolf-Rayet type come from? It could not have formed as a result of the simple aging of a single star like the Sun or more massive. The authors believe the anomaly was the result of the fusion of the nuclei of two stars in the last stages of evolution. Originally the system was a triplet, where the two stars are very close together and the third surviving to this day is far away.
Then one of the two “congested” stars stripped off its mostly hydrogen outer layers and was largely captured by the second star. He eventually dropped the hydrogen-filled shell, too. As a result, a dense cloud of hydrogen formed, slowing the movement of the remaining helium nuclei, which eventually collapsed and coalesced.