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‘Death Star’ lasers reveal the secret battle going on at the heart of the Ant Nebula

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IT’s an enormous explosion: two symmetrical, billowing bubbles of gas reaching out to form what we call the Ant Nebula. Now the pulse of lasers has been detected rippling through its shattered heart.

The Ant Nebula is already odd. It’s shape is not a common one.

Which is why the European Space Agency’s Herschel Space Observatory took a look at it back in 2013. Even though the infra-red space telescope has long since been decommissioned, astronomers are still sifting through its mountains of data and imagery.

They’ve finally got around to looking at the heart of the Ant Nebula — some 8000 light years away.

This particular cloud is called Menzel 3. It’s made up of dense gas, so what’s going on with the dying star beneath it all is particularly difficult to observe.

Then astronomers spotted the lasers.

“Thanks to the sensitivity and wide wavelength range of the Herschel observatory, we detected a very rare type of emission called hydrogen recombination line laser emission, which provided a way to reveal the nebula’s structure and physical conditions,” Leiden University astrophysicist Isabel Aleman said.

These lasers reveal a lot about what’s going on inside.

“When we observe Menzel 3, we see an amazingly intricate structure made up of ionised gas, but we cannot see the object in its centre producing this pattern,” Aleman said.

Astronomers believe the dying star is a yellow dwarf, similar to our own. As it reaches the end of its life, it ejects outer layers of gas as the core shrinks. What remains — a white deaf — gets even hotter, ionising the surrounding gas clouds and forming a nebula.

But the shape of the Ant Nebula is odd. It’s only been seen in a handful of other cases.

It seems to have something to do with the density of the central Menzel 3 gas cloud — calculated to be some 10,000 times thicker than usual.

Something is preventing the gas from escaping.

“The only way to keep gas close to the star is if it is orbiting around it in a disc,” University of Manchester astrophysics and study co-author Albert Zijlstra says.

“In this case, we have actually observed a dense disc in the very centre that is seen approximately edge-on.

“This orientation helps to amplify the laser signal. The disc suggests the white dwarf has a binary companion, because it is hard to get the ejected gas to go into orbit unless a companion star deflects it in the right direction.”

The idea is the gas being cast off by the dying star is being caught by a nearby neighbour — a second star orbiting the first. The gas then falls to its surface — and reacts — as an accretion disc.

This is influencing the shape and composition of the gas clouds that do manage to escape.

“Herschel offered the perfect observing capabilities to detect this extraordinary laser in the Ant Nebula. The findings will help constrain the conditions under which this phenomenon occurs, and help us to refine our models of stellar evolution.”


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