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Wednesday, 30 March 2016

How an interstellar dust wisp could devastate our planet

Space looks empty, but it isn't - not completely. There's a 'soup' of dust and gas that fills the space between the stars. Called the Interstellar medium (ISM), it's thin - ranging from only a handful of atoms per cubic meter at it's thinnest, to millions of atoms per cubic centimetre and higher in places.

The ISM doesn't reach the space near Earth though: The Sun puts out a magnetic bubble which both pushes back the ISM and deflects the highest energy cosmic radiation away from us.

Above: A graphic showing the structure of the Sun's protective magnetic bubble, courtesy of NASA.
So far, so 'thank-you-very-much-mother-nature'. But there's a bit of a catch: Right now our solar system's moving through a fairly thin bit of the ISM called 'the local bubble'. That allows  the Suns' magnetic field to expand out to its fullest. But in a few thousand years we'll hit a denser patch of the ISM, called 'the G-cloud' - the local bubble is already getting turbulent, as we leave it's edge. When we reach it the magnetic bubble will be forced inwards, shrinking towards the Sun. It could be pushed as far in as the orbit of Jupiter, which would cause a serious increase in the amount of radiation hitting Earth.

Above: A map of the local ISM, showing the local cloud/bubble and the G-clouds the Sun is heading towards.

It's also possible that there are even denser regions nearby, unseen. In the worst case scenario, the magnetic bubble could be pushed inwards even further: Molecular hydrogen from the ISM would flood into the inner solar system, getting ionised and turned into a barrage of cosmic rays by the Sun. These cosmic rays would strip off Earth's ozone layer (more reading in the to this NASA report), devastating plant life and the animals that feed on plants. 

Luckily for us the distances in space are huge, so we're looking at millennia at least for such scenarios to happen. The main thing that's interesting about all this is that interstellar clouds might be responsible for some of Earth's sudden climate shifts and extinctions. Most of all it shows Earth is not a special and isolated place in the universe, but a part of it - a fact we need to consider when thinking about the future of our civilisation.

Elsewhere in the Universe:

Experimental inflatable section to be added to ISS.

Jupiter may have just been hit by a comet.

Tim Peak's Principa mission:

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