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| The origin of the laser, the Ant Nebula. Pic: NASA, ESA and the Hubble Heritage Team |
Astronomers have detected an extremely rare laser emission from the "spectacular" Ant Nebula which suggests a double star system is hidden at its core.
The rare laser blast is connected to the death of a star and was detected by the European Space Agency's Herschel space observatory.
When stars the middleweight size of our sun get to the end of their lives they shrink into dense white dwarfs, ejecting off their outer layers of gas and dust and creating a nebula.
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| A picture of a planetary nebula taken in 1997. Pic: TA Rector and BA Wolpa |
The Ant Nebula is one such cloud made of dust, hydrogen, helium and other ionised gases and the laser emission suggests that its striking appearance - which has earned it its name - is hiding an even more dramatic demise for its original star.
In space, lasers are quite different from how they appear on Earth, although they remain focused beams of light occurring at very different wavelengths and under rare conditions.
By coincidence, astronomer Donald Menzel who first observed and classified the Ant Nebula in the 1920s (it is officially known as Menzel 3 after him) was the first person to suggest that lasers could occur naturally.
The term laser originated as an acronym of "light amplification by stimulated emission of radiation", and Menzel was the first to suggest that it could occur in nebulae in space - before they had even been invented in laboratories.
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| The new image of the spectacular Orion Nebula and its associated cluster of young stars. |
Dr Isabel Aleman, lead author of a paper describing the new results, said: "We detected a very rare type of emission called hydrogen recombination laser emission, which is only produced in a narrow range of physical conditions.
"Such emission has only been identified in a handful of objects before and it is a happy coincidence that we detected the kind of emission that Menzel suggested, in one of the planetary nebulae that he discovered."
Hydrogen recombination laser emissions need a very dense gas - ten thousand times more dense than the gas in typical nebulae - close to the star.
Normally, the region of space close to the dead star is quite empty because its material has been ejected outwards, with any lingering gas falling back into the star.
But this is not the case for the gas at the core of the Ant Nebula.
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Jupiter and the Shrinking Great Red Spot
What will become of Jupiter's Great Red Spot? Gas giant Jupiter is the solar system's largest world with about 320 times the mass of planet Earth. Jupiter is home to one of the largest and longest lasting storm systems known, the Great Red Spot (GRS), visible to the left. The
Comparison with historical notes
Modern GRS data indicate that the storm continues to constrict its surface area, but is also becoming slightly taller, vertically. No one knows the future of the GRS, including the possibility that if the shrinking trend continues, the GRS might one day even do what smaller spots on Jupiter have done -- disappear completely.
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Co-author Professor Albert Zijlstra, from the Jodrell Bank Centre for Astrophysics at University of Manchester, sad: "The only way to keep such dense gas close to the star is if it is orbiting around it in a disc.
"In this nebula, 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 there is 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 laser gives us a unique way to probe the disc around the dying star, deep inside the planetary nebula."
Astronomers have not yet seen the expected second star, hidden in the heart of the Ant Nebula.
