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Astronomers have discovered a new cosmic phenomenon in which a white dwarf star has been switching “off and on”, with its brightness dipping and strengthening in just 30 minutes.
The discovery was based on observations from a NASA satellite searching for alien planets, and described as “extraordinary” by a team of astronomers at Durham University and their partners across the world.
Initially they believed the fluctuations were something that was interfering with the way the white dwarf, which is part of a binary system, was feeding from a companion star – but they did not expect the cause to be as unique as it turned out to be.
As the flow of material from a donor star to the main white dwarf is governed by gravity it should remain relatively constant, so there was no obvious reason why the star’s luminosity would change on such short timescales as were being seen.
The researchers realised what was happening was something that had never been seen before – repeated and rapid reconfigurations of the white dwarf’s surface magnetic field.
The binary system known as TW Pictoris is about 1,400 light years away from Earth.
Normally, when its white dwarf is “on”, the star feeds from its companion, glowing brightly into space – but sometimes this stops and the star dims, turning “off”.
This has been seen before, but it does not usually happen so quickly.
According to the research published in the journal Nature Astronomy, the reason is because the white dwarf has an unusually fast magnetic field which is spinning so rapidly that it blocks the stream of matter from reaching the main star.
Lead author Dr Simone Scaringi, who works at Durham’s Centre for Extragalactic Astronomy, said: “The brightness variations seen in accreting white dwarfs are generally relatively slow, occurring on timescales of days to months.
“To see the brightness of TW Pictoris plummet in 30 minutes is in itself extraordinary as it has never been seen in other accreting…
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Source : skynews
