Solved: the case of missing satellite galaxies


Modelling suggests that the Milky Way galaxy should be accompanied by a posse of smaller galaxies. So where are they?



An incredibly detailed computer simulation has just solved a decades-old mystery about the satellite galaxies that should be orbiting the Milky Way – stars blasting out winds in their death throes cut their existence short.

Andrew Wetzel from the California Institute of Technology and Carnegie Observatories in Pasadena, US and colleagues published their work in Astrophysical Journal Letters.

Previous simulations suggested there should be thousands of dwarf galaxies orbiting the Milky Way galaxy, but only around 30 have been observed.

Wetzel and his crew determined those simulations failed to adequately account for the effects of supernovae on these galaxies.

These stellar explosions blast devastating winds throughout their host galaxy – and have the capacity to essentially blow young dwarf galaxies apart before they reach maturity.

The simulation required a network of 2,000 computers to operate in parallel on the puzzle for 700,000 central processing unit (CPU) hours.

The researchers are not finished simulating yet either. They plan to use up to 20 million CPU hours simulating our galaxy to develop predictions about the very faintest dwarf galaxies that remain to be discovered.

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Angus Bezzina is a writer from Sydney, Australia.
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