Scientists strike cosmic gold

By Simon Kirby
December 14, 2006 02:52pm

AUSTRALIAN astronomers have struck gold in their search for the cosmic treasure known as planetary nebulae.

Nebulae are the mysterious and often beautiful remains of dying stars, turned into regions of glowing gas that take on wonderful shapes.

Now, in a survey of "unprecedented quality", the Anglo-Australian Observatory (AAO) has found more than 1400 previously unknown examples of the phenomena.

Using the UK Schmidt Telescope at Siding Spring Mountain, near Coonabarabran in western NSW, the AAO international team of six astronomers conducted a seven-year survey of the southern galactic plane of the Milky Way visible from Australia.

Dr Quentin Parker, who led the research, said that while the telescope was not especially large, it had a uniquely large field of view.

"It's got 40 square degrees, several times the diameter of the moon in one go," he said.

"So we can do a whole survey of the galactic plane in a short time, only five years."

The study found 900 new planetary nebulae in our own galaxy and almost 500 more in the neighbouring Large Magellanic Cloud - more than had been discovered in the past 100 years.

They also found much fainter examples, planetary nebulae in much later stages of evolution, than had ever been seen before, Dr Parker said.

The phenomena are actually stars like our own sun at the end of their life, he said.

As they die, the stars shed their outer layers of gas as clouds that expand at 25km/sec.

These invisible clouds then started to glow as they became heated by increasing amounts of energy in the ultraviolet part of the light spectrum coming from the remaining hot core of the dying star, he said.

The astronomers were able to create the spectacular colour images by taking photographs in different bands of light, as the gas glows in a variety of emission lines, or light frequencies.

"You also have this amazing variety of shapes ... they can have an incredibly beautiful round shape, like glowing cosmic baubles", Dr Parker said.

"Or they can look like Xs, an hourglass, a butterfly or they can have torturous shapes, irregular or look like wedding band or an ellipse."