The Earth could be right in the firing line of a Milky Way death-star a massive supernova explosion, which may shower the planet's biosphere with a burst of destructive gamma-rays, new research says.

The hot and highly unstable star, known as a Wolf-Rayet, is part of a spiral nebula in the constellation of Sagittarius and is in the final stages of collapse.

University of Sydney astronomer Peter Tuthill warns it could explode "relatively soon", which in astronomical parlance means any time within the next few hundred thousand years.

For most people, the term death-star conjures images of the planet-destroying space station in Star Wars movies.

While Dr Tuthill's colorful spiral is far more beautiful than that rather ugly and menacing grey sphere, it is no less deadly.

"It's 8000 light years away, but that time frame is the equivalent of just down the road for astronomers. We know it's certain to go off, and the Earth seems to be looking right down the rifle barrel, but there's no need to panic and cash in the insurance policy or the family heirlooms," he said. "The Earth isn't likely to be blown away, and there are plenty of uncertainties about whether the gamma rays will pass to one side, like side-stepping a rifle bullet."

Dr Tuthill discovered the spectacular pinwheel nebula, known as WR104, eight years ago while using the world's largest telescope at the Keck Observatory in Hawaii. At the heart of the system is a pair of hot stars, circling one another, with colliding dust-laden winds and plumes of gas "entangled and twisted by the orbital motion". The system rotates in a circle every eight months, "keeping precise time like a jewel in a cosmic clock".

Dr Tuthill has published new images of WR104 in the latest Astrophysical Journal, using a series of time-lapse movie frames taken over six years which have been stacked into a single-frame composite. When first studying these images, he noticed something odd the glowing plumes of red-hot dust and gas which fanned out across a vast distance "like a giant lawn sprinkler", appeared to be laid out in the sky like a perfect spiral.

"It could only appear like that if Earth was looking exactly down the axis."

When the system finally explodes, it could send out a powerful beam of electromagnetic radiation, or gamma rays. A group of US scientists calculated that a 10-second burst of gamma rays could deplete as much as 50 per cent of the Earth's ozone layer, allowing through potentially deadly radiation.

Dr Tuthill said there was scientific speculation that a gamma-ray burst from a distant star could explain evidence of previous mass extinctions seen in the Earth's fossil record.

"But there are hundreds of uncertainties. Our calculations may be slightly out, and the beam could miss completely. Besides, we're not even sure if stars like WR104 are capable of producing a gamma-ray burst."

Even if Earth isn't directly in the firing line, these cosmic events serve to remind us that "we live in a big and scary universe, although we'd like to think it's safe", Dr Tuthill said. "These things play a haunting little tune of impermanence and should make us appreciate what a fragile little jewel of a planet we live on.

"The question really boils down to whether or not WR104 could generate a gamma-ray burst when it goes supernova, and that's a question that I think the jury is still out on.

"But in any event we will have a ringside seat for a pretty impressive fireworks display."