Scientists have for the first time observed a huge thermonuclear fireball exploding from a white dwarf going nova about 14,800 light years from Earth.
Astronomers at the University of Sydney are part of the team observing a phenomenon known as a nova in the constellation of Delphinus (the Dolphin).
The research is published in the international journal Nature.
Professor Peter Tuthill, from the University’s Sydney Institute for Astronomy and co-author of the paper, says novae often play second fiddle in the popular imagination to their more famous big cousins, the supernovae.
However, he says, they are a truly remarkable celestial phenomenon.
The term nova (Latin for new) was coined when the 16th century Danish astronomer Tycho Brahe first realised that on rare occasions the unchangeable patterns of the fixed stars could be suddenly joined by bright interlopers which took days or weeks to gradually fade from sight.
Astronomers eventually traced the culprit responsible for these stellar conflagrations – an
exotic, compact star called a white dwarf whose intense gravitational field is able to strip
matter from a larger nearby companion star.
“Like a little stellar mosquito, the white dwarf continually sucks hydrogen from its partner,
forming an ocean on its surface,” he says.
“After drawing about as much mass as the entire planet Saturn, the pressure reaches a critical point, then boom.
“The stellar surface turns into one titanic hydrogen bomb hurling a fireball out into space and propelling a formerly dim, obscure star system into prominence as a nova in our night skies.”
Professor Tuthill says the ferocity of the expansion is breathtaking, engulfing a region the size of the Earth’s orbit within a day, and passing Jupiter’s orbit in less than two weeks.
Despite the enormous size of the fireball, at a distance of fifteen thousand light years, it took very special technology to be able to image it at all.
The technical challenge required magnification equivalent to watching a flower in Spain from Sydney, a distance of 12,000 kilometres.
The leader of the scientific team taking the measurements, Dr Gail Schaefer from Georgia State University, was on-hand as the data came in.
“This is the first time astronomers have been able to witness an expanding fireball as if it were in the local neighbourhood, rather than way out in the galaxy,” Dr Schaefer says.
Despite the fury of the detonation on the white dwarf’s surface, the star itself escapes relatively unscathed and continues to buzz around its host like a persistent mosquito accumulating more matter for a repeat performance at a future date.
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