Sighting of a star that turns on and off

The finding was published in ‘Nature Astronomy’. It’s a study by astronomers led by Durham University. A flickering star, a white dwarf, was spotted. They are about the size of the Earth, but have a mass closer to that of the Sun. The observed white dwarf is powered by an orbiting companion star. Astronomers saw it lose brightness within 30 minutes. This had been seen over a period of several days to months.

A star was sighted that rapidly flickers on and off.
A star was sighted that is rapidly turning on and off.
Hungry dwarf

The brightness of a white dwarf is affected by the amount of surrounding material it feeds on. In this case, something is interfering with its food supply. It is hoped that this will provide new information about accretion. In accretion, objects such as black holes, white dwarfs and neutron stars feed on the surrounding material.

What can happen for such an abrupt change? It is thought to have to do with the surface magnetic field of the white dwarf. During the white dwarf’s “on” mode..The white dwarf feeds off the accretion disk as it normally would. Suddenly, the system shuts down and its brightness plummets. Why? It happens because the magnetic field is spinning too fast. A centrifugal barrier prevents the fuel from the accretion disk from falling onto the white dwarf. During this phase, the “fuel” of the white dwarf is regulated through the “magnetic gating” (magnetic gating).

And what is that? It’s when the spinning magnetic field of the white dwarf regulates the fuel passing through a “gate” into the accretion disk. This gives rise to small, semi-regular increases in brightness observed by astronomers. After a while, the system sporadically “turns on” again. And the brightness increases back to its original level.

This phenomenon also occurs with neutron stars, like the one in this image, and black holes.
This phenomenon also occurs with neutron stars, like the one in this image, and black holes.
Undecided star

“To see the brightness of TW Pictoris plummet in 30 minutes is in itself extraordinary. It has never been seen in other accreting white dwarfs. It seems to turn on and off.”adds Dr. Simone Scaringi of the Durham University Astronomy Centre.

“This is really a hitherto unrecognized phenomenon. We will be able to make comparisons with similar behaviour in much smaller neutron stars. It could be an important step in helping us to better understand the process. And the important role of magnetic fields in this process.”.

White dwarfs are more common in the Universe than neutron stars. Since one star was sighted that turns on and off, there must be others. Astronomers hope to look for other examples of this behavior. Just look to the stars, look and look, and wait.

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