RIKEN/ASTE: Collisions generate gas in debris disks

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RIKEN/ASTE: Collisions generate gas in debris disks

Post by bystander » Thu Apr 13, 2017 8:26 pm

Collisions generate gas in debris disks
RIKEN Star and Planet Formation Laboratory, Japan | Atacama Submillimeter Telescope Experiment | 2017 Apr 12
[img3="Illustration of gas generation from the collision between objects in a debris disk (Credit: RIKEN)"]http://alma.mtk.nao.ac.jp/aste/pressrel ... i_Fig3.jpg[/img3][hr][/hr]
By examining the atomic carbon line from two young star systems—49 Ceti and Beta Pictoris—researchers had found atomic carbon in the disk, the first time this observation has been made at sub-millimeter wavelength, hinting that the gas in debris disks is not primordial, but rather is generated from some process of collisions taking place in the debris disk.

Many young stars, as well as more middle-aged stars like our sun, have “debris disks”—like the Oort Cloud in our own solar system—that are believed to be remnants of the system’s formation. Recently, radio observations have detected gas within a number of such disks, but it was not clear why the gas was there. There are two major hypotheses: either the gas is primordial gas from the original gas cloud that formed the star, or it originates from collisions between objects in the disk.

In search of a solution to this problem, a team from the RIKEN Star and Planet Formation Laboratory decided to look at emissions of carbon, which are important as they can provide clues to the origin of the gas. Normally, carbon will exist mostly in a molecular form, as carbon monoxide. Ultraviolet light from the central star will “dissociate” the atoms, creating free atomic carbon, but normally a chemical reaction—mediated by hydrogen—recombines the carbon into CO. However, if there is no hydrogen, then the reaction does not take place and the carbon remains in its atomic state. ...

Detection of Submillimeter-wave
Emission in Gaseous Debris Disks of 49 Ceti and β Pictoris - Aya E. Higuchi et al
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