Supercomputer simulation reveals how galaxies eat gas and evolve

A new simulation from a NASA supercomputer has revealed how galaxies evolve by eating the gas spread through space around them.

When stars reach the end of their life cycle they can explode as a supernova, blowing gas formed of elements made inside the star back into space.

This gas and dust collects into enormous clouds which can eventually collapse, leading to anywhere between dozens to tens of thousands of stars forming almost simultaneously.

Without showing the light from the stars themselves, the NASA simulation depicts gases moving in and out of an evolving galaxy over 13 billion years.

It shows gases in a range of colours, from purple to yellow, to indicate the density of the gas where purple is the lower density gas and yellow is higher density.

There are blue and red colours which indicate the temperature of the gas too.

What the supercomputer simulation reveals is how colder, denser gas flows in along cosmic filaments to the spots where stars are forming.

When these stars explode as supernovae they blast galactic superwinds out of the galaxy, and these are the less dense hotter gases in the simulation.

"As there is more star formation and thus more supernovae at early times, these winds become calmer as the galaxy evolves," according to NASA.

"Unlike bright galaxies that emit plenty of light for us to observe, it's far more difficult to see the dark gases in the unlit corners of the cosmos," said NASA.

"One way to do this is by finding bright sources of light - such as other galaxies - and measuring how these gases absorb that light, to get a glimpse of what's in these hidden areas.

"Scientists use such 'cosmic lighthouses' to illuminate this cosmic fog rolling in from the dark 'oceans' between galaxies," NASA explained.

But interpreting the data from these observations is very difficult.

Powerful and complicated supercomputer simulations are carried out using the Pleiades supercomputer at the NASA Advanced Supercomputing facility at the Ames Research Centre in Silicon Valley.

The simulations are then matched up with observations from the Hubble space telescope to extrapolate the properties of the gas hidden between galaxies.

NASA said: "The results tell us that this space is far from empty. It has complex structures made of churning, turbulent gases and small clouds, as well as extreme temperatures.

"Light is one of our few tools to directly observe the cosmos, but combined with scientific ingenuity and supercomputing, we can uncover so much more."