What happens when a star explodes? Surprisingly, the same thing that happens when gas explodes here on Earth.
For explosions to occur, there needs to be a build-up of pressure. Alexei Poludnenko at the University of Connecticut and his team wanted to find out is how this can happen in explosions that occur in open, unconfined spaces, such as type Ia supernova, which is when a small, very dense star called a white dwarf detonates.
Poludnenko and his colleagues wondered whether there were similarities between these stellar events and unconfined explosions on Earth, such as the accidental blast that occurred at the Buncefield fuel storage facility in the UK in 2005.
“In Buncefield there was a fuel leak and there was a fuel-air vapour cloud formed above ground,” says Poludnenko. What was unclear is how this kind of vapour cloud could hold together long enough for an explosion to occur – the same problem as the exploding stars.
To investigate, the researchers ignited a mixture of methane and air in a lab facility and measured the pressure of the resulting explosion with sensors, while also tracking the speed of the flames using a high-speed camera. They also compared this to a computer simulation of a type Ia supernova.
They found that igniting the gas mix created fast turbulence, stirring up the flames and making the burning much more vigorous, says Poludnenko. Once the burning is fast enough, this creates pressure so quickly that it doesn’t have time to dissipate, eventually causing a detonation.
The same process seems to be behind supernova explosions, says Poludnenko. “We also see in the simulations that this happens in a star, it’s the same mechanism.”
Journal reference: Science, DOI: 10.1126/science.aau7365
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