Laser signals are detected in the Nebula Center
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Laser signals are detected in the Nebula Center

Ant Nebula.

New data show that the Ant nebula radiates intense laser emission from its core. Lasers are well-known in everyday life, from special visual effects to music concerts even in health care and communications. In space, the emission of the laser is detected at very different wavelengths and only under certain conditions. Only a few of these infrared lasers are known. An international team of astronomers discovered an unusual laser emission that suggests the presence of a double-star system hidden in the heart of the spectacular nebula. The extremely rare phenomenon is linked to the death of a star and was discovered in observations made by the Herschel Space Observatory of the European Space Agency (ESA). When the low-to-medium-weight stars, like our sun, approach the end of their lives, they end up becoming white and dense dwarf stars. In the process, they expel their outer layers of gas and dust into space, creating a kaleidoscope of intricate patterns known as a planetary nebula. Our Sun is expected to form a planetary nebula one day.

Herschel's recent observations showed that the dramatic disappearance of the central star at the core of the Ant Nebula is even more theatrical than the implicit in its colourful appearance in visible images – such as those taken by the Hubble space Telescope NASA/ESA. Coincidentally, the astronomer Donald Menzel, who first observed and classified this planetary nebula in particular in the 1920 (is officially known as Menzel 3, in honor of him) was also one of the first to suggest that under certain conditions the Amplification of natural light by stimulated emission of radiation ' (light amplification by stimulated emission of radiation) – from which the acronym ' laser ' drifts – could occur in nebulae in space. This was well before the discovery of lasers in laboratories. Dr. Isabel Aleman, the main author of an article describing the new results, said:

We detected a very rare emission type, called hydrogen recombination laser emission, which is produced only in a narrow range of physical conditions. Such an issue 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.

This type of laser emission needs very dense gas near the star. The comparison of observations with models showed that the density of the emitted gas of the lasers is about 10000 times denser than the gas seen in the typical planetary nebulae and the lobes of the Ant Nebula itself. Usually, the region next to the dead star – in this case, the distance between Saturn and the sun – is quite empty, because its material is ejected out. Any remaining gas would soon fall back on it. Co-author, Prof. Albert Zijlstra, of the Centro Jodrell Bank of Astrophysics of the University of Manchester, added:

The only way to keep a gas so dense near the star is if it's orbiting around it on a disk. In this nebula, we actually observe a dense disk in the center that is seen roughly on the edge. This guidance helps amplify the laser signal. The disk suggests that there is a binary companion, because it is difficult to get the ejected gas into orbit, unless a companion star deflects it in the right direction. The laser gives us a unique way of probing the disk around the star that is dying at the bottom of the planetary nebula.

Astronomers have not yet seen the expected second star, hidden in the heart of this nebula… Source)


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