Astronomers see star ‘turn on and off’ in major discovery – .

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Scientists saw a white dwarf blinking for the first time.
In what they described as “unexpected” discoveries that do not fit with existing understandings of the universe, the researchers were able to watch the star go extinct, become bright and then dark.

It was observed through a NASA telescope typically used to hunt exoplanets or distant worlds in other planetary systems.

White dwarfs are the end state of most stars: after burning the hydrogen that powers the star, they become dense packets that glow in the night sky.

They are about as big as the Earth, but have a mass more comparable to our Sun.

The white dwarf observed by researchers is known to accret or feed on a companion star in orbit.

It has been seen to lose brightness within 30 minutes, a process that previously only occurred in the accumulation of white dwarfs over a period of days to months.

Because the brightness of a growing white dwarf is affected by the amount of surrounding material it feeds on, researchers suggest something is interfering with its food supply.

Researchers at Durham University hope this discovery will help them learn more about the physics behind accretion – where objects like black holes, white dwarfs and neutron stars feed on the surrounding material of stars. neighbors.

Use of NASA’s transit exoplanet satellite (Tess) to observe the phenomenon in the binary system of the white dwarf, TW Pictoris, which is about 1,400 light years from Earth.

TW Pictoris consists of a white dwarf that feeds on a surrounding accretion disk fueled by hydrogen and helium from its smaller companion star.

As the white dwarf eats – or accumulates – it becomes brighter.

The satellite allowed the team to see sheer drops and never-before-seen increases in brightness in an accumulating white dwarf over such short time scales.

The researchers believe that what they are witnessing could be reconfigurations of the surface magnetic field of the white dwarf.

During the “on” mode, when the brightness is high, the white dwarf feeds on the accretion disk as it would normally.

Suddenly and abruptly, the system shuts down and its brightness collapses, astronomers observed.

The researchers say that when this happens, the magnetic field spins so fast that a barrier prevents fuel from the accretion disk from constantly falling on the white dwarf.

During this phase, the amount of fuel that the white dwarf is able to feed on is regulated by a process called magnetic gating.

Lead author Dr Simone Scaringi, Center for Extragalactic Astronomy at Durham University, said: “The variations in luminosity observed in the accumulation of white dwarfs are generally relatively slow, occurring on scales of time from a few days to a few months.

“Seeing the brightness of TW Pictoris drop in 30 minutes is, in itself, extraordinary as has never been seen in other accretive white dwarfs and is totally unexpected based on our understanding of how these systems are supposed to power. the accretion disk.

“It seems to turn on and off.

“This is really a previously unrecognized phenomenon and because we can draw comparisons to similar behavior in much smaller neutron stars, it could be an important step in helping us better understand the process by which other accreting objects feed on the surrounding material and the important role of magnetic fields in this process.

The research, published in Nature Astronomy, was funded in the UK by the University of Durham.

The research team also included the Italian National Institute of Astrophysics, the South African Astronomical Observatory, the University of Cape Town and the Free State University, both also in South Africa, the University Radboud, in the Netherlands, the University of Southampton, in the United Kingdom, and the University of Notre Dame, in the United States.

Additional reports by agencies

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