A team of astronomers have captured the first images of a thermonuclear fireball from a nova star, allowing them to track the explosion as it expanded. It revealed with “unprecedented clarity” how the fireball evolves as the gas fuelling it expands and cools. These explosions are quite unusual events caused by a white dwarf star, which is a burned-out remnant of a star made of very dense material – a teaspoon full of this stuff weighs tonnes. The white dwarf star is like a mosquito that buzzes around the companion star, slowly sucking hydrogen from its companion through a little gravitational straw. This created an “ocean” of hydrogen on its surface a few hundred meters thick, with the pressure at bottom of the ocean eventually reaching critical mass and triggering a thermonuclear explosion called a nova. You get a fireball, like a massive hydrogen bomb that propagates outwards. Despite the massive detonation, the white dwarf escapes relatively unscathed and continues to circle around its host accumulating more matter so the cycle can repeat again. Measuring the expansion allowed researchers to establish the nova was about 14,800 light years away from the sun, meaning that the explosion witnessed in August 2013 actually took place nearly 15,000 years ago. When last measured 43 days after the detonation, the nova had expanded nearly 20-fold, at a velocity of more than 600 km per second.
Posted on: Mon, 27 Oct 2014 08:20:43 +0000
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