Saturday, October 23, 2021

Astronomers capture for the 1st time white dwarf star "turning on and off"

For the first time, astronomers have spotted a white dwarf star "turning on and off" quickly. Located about 1,400 light-years from Earth, the star performed the phenomenon for just 30 minutes and the record was released this Monday (18) in the scientific journal Nature Astronomy. According to the scientists, the object is in the TW Pictoris binary system, composed of two white dwarfs, which are those whose hydrogen fuel has completely run out. 

The unexpected change in brightness was observed in only one of these stars, which is feeding from an accretion disk around its companion. The more it "nourishes", the more its light increases. The phenomenon could be followed using NASA's Transiting Exoplanet Survey Satellite (TESS) space telescope. The observations were carried out by an international team, led by an expert from the University of Durham, UK. The group saw abrupt drops and surprising brightness increases. 

Scientists believe there is something interfering with the white dwarf's feeding — probably its magnetic field. When her glow is “on”, the star picks up material from the companion's disk. When its luminosity dims, it's because the field rotates so fast that a centrifugal barrier prevents the disc's fuel from falling onto the white dwarf. In other words, the star's rotating magnetic field acts as a “magnetic gate” that regulates the entry of helium and hydrogen into the accretion disk. This ends up altering the luminosity that is seen by astronomers until the system “turns on” again and the light returns to normal.

 

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