An unusual white dwarf – about the same size as the moon, but more massive than our sun – could potentially turn into a true neutron star.
Astronomers have discovered the smallest and largest white dwarf ever. It can be read in the magazine nature. The particular white dwarf is about the same size as the Moon, but larger than our Sun. Burning ember formed when two less massive white dwarfs fused together. And this star’s future may be just as special as his past. Because researchers expect that a small white dwarf can turn into a neutron star.
As a star ages, hydrogen fusion in the star’s core stops and it swells. Then a red giant is created. As the star then blows its outer layers of gas and dust, the core shrinks, leaving a white dwarf. The star has reached the end of his life. Such a white dwarf is roughly the size of Earth, but has a much greater density (a teaspoon of white dwarf matter weighs the equivalent of an elephant on Earth!). The dying process also has a huge impact on planets orbiting such a star. Most planets gravitate toward and swallow the star, and our sun will end up becoming a compact white dwarf in five billion years. In fact, about 97% of stars turn white dwarfs.
It may seem a bit contradictory. Because how can a star also be the smallest and heaviest? This is how you work with white dwarfs. Small white dwarfs are heavier than large dwarfs. This is due to the fact that in white dwarfs – as described above – nuclear fusion no longer occurs so that it balances their gravity in ordinary stars.
How did the special white dwarf – called ZTF J1901 + 1458 – get such a prestigious title as the smallest and largest? As mentioned, this relates to the merging of two separate white dwarfs. Although our Sun is lonely, many other stars orbit each other in pairs. Stars age together, and if each weighs less than eight solar masses, they develop into white dwarfs.
The current study provides insight into what could happen after that stage. White dwarfs orbiting each other lose energy in the form of gravitational waves and merge. If the dead stars together have sufficient mass, a supernova Ia explosion occurs. But if they stay below a certain mass threshold, they combine to form a new white dwarf, much larger than any of the ancestors. Then this star rotates faster on its axis and develops a strong magnetic field.
What is a type 1 supernova?
This type of supernova occurs in narrow binary star systems, where one star is a white dwarf and the other a red giant (or second white dwarf). Type Ia supernovae play an important role in our understanding of the universe. A Type Ia supernova is the brightest type of supernova: radiating more than a billion times the energy of our Sun. This allows them to see them at great distances. In addition, in their violent explosions, they eject many elements from which new stars and galaxies appear.
Astronomers believe that ZTF J1901 + 1458 followed the last evolutionary path. Its predecessors fused and produced a white dwarf 1.35 times as massive as our sun. The white dwarf has an intense magnetic field that is a billion times stronger than that of our Sun. In addition, it rotates at an insane rate, making one revolution every seven minutes (the fastest known white dwarf rotates every 5.3 minutes).
Who doesn’t find this cool enough; The ZTF J1901 + 1458 receiver can also be special. According to the researchers, the young white dwarf can collapse even more. In this case, the star turns into a neutron star. They usually form when a star, much larger than our Sun, explodes in a supernova. “It’s still very speculative, but it’s possible that the white dwarf could become so massive that it could turn into a neutron star,” said researcher Ilaria Kayazu. “In this case, the electrons are captured by the protons in the nucleus, forming neutrons. When enough electrons are captured, the nucleus collapses.” Then a real neutron star is created.
Researchers believe that objects like ZTF J1901 + 1458 are common in our Milky Way. They infer this from the white dwarf’s proximity (only 130 light-years away) and its young age (the star is 100 million years old at most). This could mean that a large percentage of other neutron stars are born in a similar way. So the researchers plan to find more white dwarfs like ZTF J1901 + 1458. “There are a lot of questions that still need to be answered,” Chiazu said. How quickly do white dwarfs merge and is this enough to explain the number of Type Ia supernovae? How is a strong magnetic field generated during such events and why is there such a diversity in magnetic field strength among white dwarfs? Finding so many white dwarfs born from Mergers will help mysteriously solve this problem.”