Galactic Wind that Stops Early Galaxies Blowing Themselves Apart is Detected by Scientists


For the first time, a powerful ‘wind’ of molecules has been detected in a galaxy located 12 billion light-years away.

The wind stops early galaxies blowing themselves apart during their formation, scientists say.

Until now, astronomers were unable to directly observe these powerful mechanisms in the early universe that prevent galaxies from growing too big, too fast.

The galaxy, known as SPT2319-55, was discovered by the National Science Foundation’s South Pole Telescope.

University of Texas at Austin astronomer Justin Spilker made the finding by looking at the universe when it was less than ten per cent of its current age.

The find sheds light on how the earliest galaxies regulated the birth of stars to keep from blowing themselves apart.

‘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,’ Dr Spilker said.

Some galaxies such as the Milky Way and Andromeda have relatively slow and measured rates of star-birth, with about one new star igniting each year.

Other galaxies, known as starburst galaxies, forge hundreds or even thousands of stars each year.

This furious pace, however, cannot be maintained indefinitely.

To avoid burning out in a short-lived blaze of glory some galaxies throttle back their runaway starbirth by ejecting vast stores of gas into their expansive halos.

This is where the gas either escapes entirely or slowly rains back in on the galaxy, triggering future bursts of star formation.

Dr Spilker’s observations were made with the Atacama Large Millimeter/submillimeter Array (ALMA).

They show for the first time that a powerful galactic wind of molecules in a galaxy seen when the universe was only one billion years old.

This shows how certain galaxies in the early universe were able to self-regulate their growth so they could continue forming stars across cosmic time.

Astronomers have observed winds with the same size, speed and mass in nearby starbursting galaxies.

However, the new ALMA observation is the most distant unambiguous outflow ever seen in the early universe.

ALMA was able to observe the object using gravitational lens of a different galaxy that sits almost exactly along the line of sight between Earth and SPT2319-55.

Gravitational lensing – the bending of light due to gravity – magnifies the background galaxy to make it appear brighter, which allows the astronomers to observe it in more detail than they would otherwise be able to.

Astronomers use specialized computer programs to unscramble the effects of gravitational lensing to reconstruct an accurate image of the more-distant object.

This lens-aided view revealed a powerful wind of star-forming gas exiting the galaxy at nearly 800 kilometres per second.

Rather than a constant, gentle breeze, the wind is hurtling away in discrete clumps, removing the star-forming gas just as quickly as the galaxy can turn that gas into new stars.

Molecular winds are an efficient way for galaxies to self-regulate their growth, the researchers note.

These winds are probably triggered by either the combined effects of all the supernova explosions that go along with rapid, massive star formation, or by a powerful release of energy as some of the gas in the galaxy falls down onto the supermassive black hole at its center.

‘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,’ Dr Spilker concluded.

‘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.’


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