The discovery of more than 1,000 glowing planetary nebulae could help balance cosmic accounts, says an international team of astronomers.

The researchers say that their discovery could help them calculate what happens to stars' missing matter, mass that seems to be lost when they die.

Dr. Quentin Parker of Australia's Macquarie University in Sydney and colleagues say they have found 900 new planetary nebulae in the Milky Way and 500 in the neighbouring Large Magellanic Cloud.

"Planetary nebulae are the death throes of stars," said Parker, who is also with the Anglo-Australian Observatory.

They are glowing regions of ionized gas that average-sized stars like the sun throw off when they get old.

The gas ejected by the dying star interacts with the environment around it, such as the interstellar medium, to form weird and wonderful shapes.

These have been given names like the cat's eye, hourglass, helix, ant and red spider.

Missing matter

Studying planetary nebulae helps tell astronomers about how stars' matter is recycled from old to new stars.

Nebulae last for tens of thousands of years, so it's important for astronomers to study both young and old ones.

In general, it has been a lot easier for them to find younger nebulae because they glow brighter.

But Parker and colleagues have been able to find the fainter older ones and are now confident that they have representative sample of different ages, especially of nebulae close to the sun.

The mystery about dying stars is that they seem to lose much more mass than what appears to be thrown off in their nebulae. Some 85 per cent of the mass appears to be unaccounted for.

Parker hope that analyzing the hundreds of new nebulae discovered will help explains where the extra mass goes.

In the team's more detailed study of the Large Magellanic Cloud the team has found numerous extremely faint haloes around 60 per cent of the planetary nebulae there.

Parker said one theory is that these represent pulses of mass shed from the star before the nebula itself is ejected.

"We suspect this is where much of the missing mass resides," he said.

A boost in numbers

While it took over 100 years to discover 1,500 planetary nebulae in this galaxy, Parker and colleagues' recent discovery boosted the number by 60 per cent in just a few years.

The 500 found in the Large Magellanic Cloud adds to 300 already known in that galaxy.

The researchers made the discovery using Britain's Schmidt Telescope at Siding Spring Observatory in western New South Wales.

They used a special filter on the telescope to highlight a hallmark wavelength of hydrogen gas in planetary nebulae.

Parker hopes to take images of some of the new planetary nebulae using the high-resolution capability of the Hubble Space Telescope.