Winner sheds light on how a star is born

Adela Talbot // Western News

Western postdoctoral scholar Andrew Pon recently placed first in the university’s 3MR-Three Minute Research communication competition for postdoctoral scholars for his presentation on star formation.

The analogy Andrew Pon uses is that of filling a bathtub.

There are two ways to do it. You can turn on the tap and let a steady stream flow until the tub is full. Or, you can use a bucket, filling it at a pump, walking back and forth to the tub, with intermittent bursts of water, eventually, filling it.

That second option might just explain how stars form, according to Pon, a postdoctoral fellow at Western.

“How do you actually get mass from a large cloud – a large nebula – down into what will eventually be a star?” asked Pon, who placed first in the university’s 3MR-Three Minute Research communication competition for postdoctoral scholars last month for his presentation on star formation.

According to Pon, a star may be born as a ‘proto star’ – an object the size of Jupiter, embedded in a much larger cloud many thousand times larger than our solar system. Gravity then slowly pulls at the mass to form a star. That’s the belief, although astrophysicists are still determining how this actually happens.

“We can calculate how bright we think the proto star should be, if everything flowed in fairly steadily and uniformly. The problem is, when we go out, and look at how bright proto stars actually are, we find they are typically much dimmer than they should be – 10 times fainter than they should be,” explained Pon, whose work is partially funded by the Canadian Institute for Theoretical Astrophysics.

“One of the solutions proposed is maybe the mass of the proto star accretes in bursts – like the (second way of filling the bathtub). With stars, it could be the same thing; it could be very intermittent, how all this gas gets dumped on the proto star.”

Astrophysicists believe a proto star may sit idle for some time. It is possible that the proto star grows in a burst, with a mass influx of gas, after which it eventually accumulates enough mass to start fusing elements in the core, becoming an actual star.

All of this boils down to the desire to answer basic questions: How did the solar system form? Why, when and for how long do proto stars stay dim? If they don’t form in intermittent bursts, where is the energy going?

Pon is working with international astrophysicists, observing different regions of proto stars in formation in the galaxy, taking monthly images of them to measure their brightness and any change therein. To do this, he is using the Maxwell Telescope in Hawaii, operated by the East Asian Observatory, with additional funding support from the Science and Technology Facilities Council of the United Kingdom and participating universities in the United Kingdom and Canada.

“If they’re getting brighter, it means we’ve probably seen the start of a star. If they’re getting dimmer, it probably means we’ve caught the end of (its formation),” Pon noted.

“Ideally, we’d love to see a star stay dim, then see a sudden brightening and a dimming back down. We would love to know about the accretion bursts – when they are gaining mass – and how long that lasts. A month? Ten years? One hundred years? We don’t know how quickly it will go through the phase or how much mass it will gain. Is it 10 per cent brighter? Or 10 times brighter?”

A three-year project, Pon’s team has been looking at data for one year. There is another team working with The James Clerk Maxwell Telescope that has identified a potential proto star heading towards a brightening trajectory, and the project is an ongoing partnership.