Milky Way robs neighbouring galaxies of gas

Milky Way robs neighbouring galaxies of gas and uses its gravitational pull to hoard chemicals which could form new stars and planets

  • Researchers used data from the Hubble Space Telescope to survey gas flows
  • Supernovae and stellar winds blast gas into the galaxy’s halo, which falls back in 
  • They were surprised to find more gas flowing into our galaxy than is going out
  • The relative mass of the Milky Way may let it siphon gas from its satellite galaxies

Our galaxy is stealing gas from its smaller satellite galaxies, enabling it to form stars and planets at a greater rate, a new study has found.

Galaxies are big recyclers. Supernovae and stellar winds blow gas out of the galactic disk into the surrounding halo, where it falls back onto the galaxy to form new stars.

Experts used data taken by the Hubble Space Telescope to survey these flows of gas in and out of the Milky Way, and were surprised to find more gas coming in. 

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Our galaxy is stealing gas from its smaller satellite galaxies, enabling it to form stars and planets at a greater rate, a new study has found

Astronomer Andrew Fox of the Space Telescope Science Institute in Baltimore, Maryland, and colleagues analysed 200 past ultraviolet observations of the halo of gas that surrounds our galaxy taken by the Hubble Space Telescope.

Hubble used ultraviolet measurements because the gas clouds that make up the galactic halo are only visible when viewed via this part of the light spectrum.

Light from distant quasars — the extremely bright cores of active galaxies which are powered by supermassive black holes — were used to detect the gas clouds.

The gases absorb certain parts of the quasars’ light, allowing the researchers to trace its location. The directions of the gases’ movements were determined by how the light’s frequency was correspondingly shifted. 

From this, they were able to gain an unprecedented look at the gas flow across the galaxy and create the first-ever galaxy-wide gas inventory. 

‘The original Hubble COS observations were taken to study the universe far beyond our galaxy, but we went back to them and analysed the Milky Way gas in the foreground,’ said co-author Rongmon Bordoloi of the North Carolina State University.

‘It’s a credit to the Hubble archive that we can use the same observations to study both the near and the more distant universe.’ 

‘We expected to find the Milky Way’s books balanced, with an equilibrium of gas inflow and outflow, but 10 years of Hubble ultraviolet data has shown there is more coming in than going out,’ said Dr Fox.

Understanding the balance between these two processes is important, because such regulates the amount of material available to form new stars and planets. 

It is unclear, however, exactly where this extra gas is coming from — although a couple of possibilities present themselves.

One is that the gas could be being collected from the void between galaxies.

However, Fox believes that the Milky Way is likely also raiding the gas ‘bank accounts’ of its small satellite galaxies, using its greater gravitational pull to siphon off their resources. 

Alternatively, hotter gas could be playing a role. The present study only examined cooler gases. 

Experts used data taken by the Hubble Space Telescope to survey these flows of gas in and out of the Milky Way (pictured here as seen from the Earth), and were surprised to find more gas coming in. The laser seen in the picture helps the telescopes, in the foreground, focus

‘Studying our own galaxy in detail provides the basis for understanding galaxies across the universe,’ said paper coauthor and astrophysicist Philipp Richter of the University of Potsdam in Germany.

‘We have realised that our galaxy is more complicated than we imagined.’ 

At present, the Milky Way is the only galaxy for which we have sufficient data to perform such a comprehensive accounting of gas in and outflows.

With their present study complete, however, the researchers will be both investigating the source of the additional gas inflow and working to see if other large galaxies — such as the neighbouring Andromeda galaxy — behave in the same way. 

The full findings of the study were published in the journal The Astrophysical Journal. 

WHAT DOES THE HUBBLE SPACE TELESCOPE DO?

The Hubble Space Telescope (pictured) recently captured a stunning image of a galaxy 20 million light years away

The Hubble Space Telescope was launched jointly by NASA and the European Space Agency.

The Hubble is a space-based and long-term observatory.

The Hubble observes ultraviolet wavelengths, which the atmosphere filters out, and it collects visible light.

‘The Hubble Space Telescope has made some of the most dramatic discoveries in the history of astronomy,’ a statement on the Telescope says.

The machinery sits more than 370 miles above earth.

It can pick up on light via its ‘eyes’, which are five times more focused than ground-based telescopes.

The Hubble focuses on areas in deep outer space ‘where some of the most profound mysteries are still buried in the mists of time’.

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