Scientists of the Arms Observatory (Ireland) and the University of West Ontario (Canada) revealed that with age in some white dwarfs, strong magnetic fields are formed. At the same time, at a minimum, one of the four degenerate stars will become magnetic. New data helps to explain the appearance and development of magnetic fields at the final stage of the life of the stars of the main sequence, to which the sun also belongs. The mystery of the mystery of white dwarfs is reported in an article published in the reproducts of the ARXIV preprints.
More than 90 percent of the stars of our galaxy will complete their existence in the form of white dwarfs. Although many have a magnetic field, it is still unknown, what is the mechanism of its occurrence, and whether it develops during the white dwarf cooling phase. Over time, white dwarfs become cold and more dull, and astronomers most often explore hot and bright stars. In addition, more massive white dwarfs have smaller sizes and also emit less light, so observations are focused on less heavy and young stars.
In the new work, scientists took advantage of spectropolarmetric observation methods that are sensitive to magnetic fields. They analyzed all the white dwarfs located within 20 parses from the Sun, including those previously not observed. It turned out that the magnetic fields were rare at the beginning of the life of white dwarfs when the star enters the cooling phase. Consequently, the magnetic field is not a characteristic of a degenerate star from the moment of birth.
This picture is completely different from what is observed, for example, in magnetic AP and BP stars of the main sequence, in which the intensity of the field with age is rapidly decreasing. Therefore, magnetism in white dwarfs is a completely different phenomenon than magnetism in Ap- and BP stars. The frequency of the magnetic field in white dwarfs correlates with a lot of stars, and the fields appear more often after the carbon-oxygen stars core crystallizes.