science

Galactic wind that controls star birth detected in depths of universe



Powerful winds from the dawn of the universe have been detected by scientists for the first time – 12 billion light years away from Earth. 

Travelling at 500 miles per second, astronomers think these gusts of cosmic gas are instrumental in controlling the emergence of stars and the galaxies they are part of.  

 

Galaxies are complicated, messy beasts, and we think outflows and winds are critical pieces to how they form and evolve, regulating their ability to grow,” explained University of Texas at Austin astronomer Dr Justin Spilker, who led the research. 

Using observations from the ALMA observatory in northern Chile, Dr Spilker and his colleagues were able to detect traces of these winds from a time shortly after the Big Bang, when the universe was only one billion years old.

Galaxies such as our own, the Milky Way, have a history of relatively slow, controlled star birth, with about one new star emerging every year.

However, thousands of stars can emerge in the same space of time in starburst galaxies. 

These will rapidly consume the gas reservoir they rely on to form new stars, so their lifespans tend to be relatively short.

The ALMA observatory, aided by a gravitational lens, imaged the outflow, or ‘wind,’ from a galaxy seen when the universe was only one billion years old.The circular, double-lobe shape of the distant galaxy is due to the distortion caused by the cosmic magnifying effect of an intervening galaxy. (ALMA/J. Spilker/S. Dagnello)

Galaxies avoid this early death when they eject vast quantities of gas early on, slowing down the rate of star formation and producing galactic winds.

These astronomical weather patterns can be seen in nearby galaxies using conventional X-ray and radio techniques from Earth. 

However, identifying them in the farthest reaches of the universe, which provides insight into its early years, is far harder.

ALMA was able to pin down the effect in the galaxy known as SPT2319-55 using gravitational lensing, the process by which gravity bends light and in doing so magnifies events that would otherwise be impossible to observe using existing technology.

This technique has previously allowed scientists to identify planets far beyond the Milky Way for the first time.

In their distant galaxy, the team was able to detect large amounts of cold gas flowing outwards from the ancient galaxy at approximately the same rate as new stars are forming.

“So far, we have only observed one galaxy at such a remarkable cosmic distance, but we’d like to know if winds like these are also present in other galaxies to see just how common they are,” said Dr Spilker. 

“If they occur in basically every galaxy, we know that molecular winds are both ubiquitous and also a really common way for galaxies to self-regulate their growth.”

As gas is ejected away from the galaxies themselves, it will either drift out into the wider universe or gradually rain back down into the galaxy and form stars in a feedback loop.

The winds likely form either as supernovas within the galaxies explode or due to the effects of supermassive black holes releasing bursts of energy.



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