2023-06-19 12:45:29
The discovery of a rare white dwarf star supports the existence of a phenomenon once considered impossible.
White dwarfs are small, dense stars, usually about the size of a planet. They form when a low-mass star has burned up all its nuclear fuel, losing its outer layers. The resulting star no longer has the nuclear activity of active stars, but it still retains a lot of heat and therefore continues to shine.
A recent finding supports the idea that, under the right circumstances, a pair of stars made up of a white dwarf and a red dwarf can eventually behave like a pulsar. Normally, pulsars are neutron stars (corpses of stars denser than white dwarfs but less than black holes) with extremely rapid rotation and emitting electromagnetic waves from their magnetic poles. The misalignment of the magnetic poles with respect to the axis of rotation of the neutron star causes the beams of radiation to rotate in the same way as the spotlights of a maritime lighthouse, sending pulses of electromagnetic waves towards any distant observers who are at points on the planet. cosmos to which these pulses reach.
The new discovery of the white dwarf star accompanied by a red dwarf reproducing pulsar-like behavior is the second of its kind. The first such system to be discovered was AR Scorpii (AR Sco) in 2016.
White dwarf pulsars include such a star that strafes its neighbor (a red dwarf) with powerful beams of particles and radiation, causing the entire system to brighten and dim dramatically, at regular intervals. The mechanism responsible for this involves strong magnetic fields, but very little is known about it.
Artist’s impression of a white dwarf pulsar, with its companion red dwarf star. (Illustration: Mark Garlick / University of Warwick)
An increasingly accepted theory that explains the strength of magnetic fields is the “dynamo model,” according to which white dwarfs have dynamos (electrical generators) at their core, just like Earth does, but much more powerful. However, to test this theory, one or more other white dwarf pulsar cases needed to be found to test whether the predictions hold.
And now, the new case that the scientific community was looking for has finally been found. Ingrid Pelisoli’s team at the University of Warwick in the UK have thoroughly investigated this new white dwarf pulsar, named J191213.72-441045.1 (J1912-4410 for short). Observations support the dynamo model.
Located 773 light-years from Earth and spinning 300 times faster than our planet, the white dwarf is about the same size as Earth, but at least as massive as the Sun. This means that a teaspoon of material a white dwarf would weigh about 15 tons. White dwarfs begin their lives at extremely high temperatures before cooling off over billions of years, and the low temperature of J1912-4410 suggests that this star is remarkably old.
The new study is titled “A 5.3-min-period pulsing white dwarf in a binary detected from radio to X-rays.” And it has been published in the academic journal Nature Astronomy. (Source: NCYT from Amazings)
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