In deep space, it's kill or be killed.

Australian scientists have photographed two galaxies, including the Milky Way, teaming up to bully and consume another smaller galaxy.

Large galaxies like our own need to continually eat smaller galaxies to get fuel for making new stars. Otherwise, they run out of fuel and die. It's the circle of life – in space.

"The Milky Way has to eat galaxies to keep building stars. Our galaxy needs food, and these are kind of snacks," says Australian National University astronomer Professor Naomi McClure-Griffiths.

Professor McClure-Griffiths and her team are interested in how galaxies form, and how they die.

The best way to find that out, they say, is to follow the hydrogen.

Hydrogen fuels stars and is the basic building block of all galaxies. Inside a galaxy it swirls around until it is compressed by gravity into a new star. A galaxy that has a lot of hydrogen can make new stars and expand in size.

The team is studying the Small Magellanic​ Cloud, a dwarf galaxy that orbits the Milky Way. The Cloud has several hundred million stars – a small fry compared to the Milky Way's hundreds of billions.

The Cloud, which is about 200,000 light years away, is visible to the naked eye as a fuzzy patch in space. It is one of the most distant objects visible without a telescope.

But it will soon be gone. The Cloud is in the process of being devoured by two galaxies, and over the next several billion years will be fully incorporated into them.

A new image, taken by the CSIRO's new Australian Square Kilometre Array Pathfinder radio telescope, captures the hidden evidence splattered across the crime scene.

The telescope takes images using radio waves, allowing it to spot things otherwise invisible. When the scientists turned it to the Small Cloud, it revealed the galaxy's hydrogen was being sucked away by the gravity of two nearby and much larger galaxies – the Milky Way and another galaxy known as the Large Magellanic Cloud.

Stars in a galaxy explode as they reach the end of their life, spraying hydrogen out across space. A galaxy would normally hold on to that hydrogen and use it to build new stars.

But our galaxy's size advantage means its gravity is far stronger than the Small Cloud's, allowing the Milky Way to extract its gas. With the extra fuel,  it will be able to build new stars and expand.

"As you get out to the outer edges of the galaxy you can see where it's being ripped apart and blowing itself to smithereens," Professor McClure-Griffiths says.

"The Small Magellanic Cloud is like the little guy that's being bullied by the Milky Way and the Large Magellanic Cloud – and it's falling apart in the process."