Young star is born of fire

In a galaxy far, far away (or somewhere a little closer) at around 22,000 light-years away, a young star is growing up and the way it has undergone its growth spurt has been observed for the very first time from earth.

“Big deal” some of us might exclaim before asking why we’re not looking at objects closer to earth, like huge asteroids careening towards us? The reason this is important, according to a team of scientists from around the world working on the project,  is the discovery represents a massive leap in our understanding of space.

So what happened? Let’s set the scene. Think of a cold winter’s night and you throw another log on the fire or (more dramatically) two actors walking slowly away from a gigantic explosion in a Hollywood blockbuster( like Will Smith and Martin Lawrence in Bad Boys). With both, there’s that definite moment when the fire or explosion springs to life.

This is what happened out in space with a likely protostar at the edge of the galaxy. The difference here is rather than the fireball destroying the log or car, it’s actually helping the object grow. It sounds rather dramatic but our stars might be literally forged from fire.

As for this young star experiencing growing pains, Australian astronomers working on radio telescopes scattered across the southern hemisphere have recently witnessed the log-throwing-on moment – that crackling instant when sparks fly from a stellar furnace, and they’ve published their results in the prestigious Nature Astronomy.

Known as an accretion burst, the explosion came in the form of a “heatwave” of maser radiation from a protostar about eight times the size of our Sun called G358-MM1, which is about 22,000 light-years away from Earth.

“This is the first time we managed to observe an accretion burst in real time from its beginning,” says the paper’s co-author Gabor Orosz from the University of Tasmania.

“Now we have proved that accretion bursts can happen in high-mass stars. They were known to exist in low-mass stars like our Sun, but they have never been seen directly in high-mass ones.”

This observation may help fill an important gap in our knowledge of how massive stars form. One theory is that they start off regular-sized and gradually gain, or accrete, additional mass.

This theory predicts that intense accretion bursts lasting from a few weeks to several months should occur when protostars gain mass as large fragments of surrounding matter fall into the stars.

Image: A generic depiction of the structure of a protostar from NASA Image Credit: NASA/JPL-Caltech/R. Hurt (SS

As the mass merges with the star it creates bright flashes of maser radiation – like a laser, but in the microwave end of the spectrum.

This is then followed by long periods of inactivity lasting from hundreds to thousands of years, the theory goes.

“This observation has the potential to open up a whole new avenue of investigation for the high-mass star formation community,” Orosz concludes.

Head image: heatwave.png: Heatwave artist impression Credit: Katharina Immer (JIVE)

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