Orion Bar

Orion Bar. Credit score: Weilbacher et al.

Molecular hydrogen (H2) makes up 99% of the chilly dense fuel in galaxies. So mapping the place stars are born principally means measuring H2, which lacks a powerful attribute signature at low temperatures. Astronomers from SRON Netherlands Institute for Area Analysis and the College of Groningen have now mapped an emission sign from the hint molecule hydrogen fluoride (HF), in a spot the place the customary hint molecule carbon monoxide is absent. They’re the first to produce a map of HF for a area in house, creating a brand new instrument to not directly map H2. Publication in Astronomy & Astrophysics on November sixth.

All throughout galaxies in our Universe, stars are dying and forming. And whereas our life on Earth is predicated on a wealthy jumble of varied components and molecules, the chilly dense fuel out of which stars kind is fairly monotonous with 99% molecular hydrogen (H2). So if you’d like to map the place stars are born, you’d higher have an excellent grasp on how to detect H2. Sadly, this materials is tough to observe due to an absence of a powerful attribute sign at low temperatures—in contrast to its atomic cousin (H) which emits radio waves at an simply distinguishable wavelength of 21 cm. Astronomers from SRON Netherlands Institute for Area Analysis and the College of Groningen have now found a brand new instrument to not directly measure H2, by mapping hydrogen fluoride (HF) and linking its abundance to that of H2.

Hydrogen fluoride

The brand new instrument comes in useful when different instruments fail, for instance in the Orion Bar, in between areas round the Orion Trapezium stars and the Orion Molecular Cloud. In these areas carbon is ionized, that means that carbon monoxide (CO)—often a dependable hint molecule to discover H2—can’t work as a tracer in this case. Floris van der Tak (SRON/RuG) and his group have been stunned to discover a attribute HF sign in knowledge from the Herschel telescope coming from the Orion Bar, as astronomers have beforehand solely detected hydrogen fluoride as a silhouette: HF absorbing different radiation. HF and H2 abundance could be linked as a result of HF is produced in a chemical response the place H2 reacts with atomic fluorine (F) to kind HF and atomic hydrogen (H). With out H2 there is no such thing as a HF.


The group, led by SRON PhD pupil Ümit Kavak, used their map of HF to study a couple of mechanisms by way of which it might emit its sign. Collisions of HF molecules with electrons and molecular hydrogen seems to be the most important mechanism. The collisions excite the HF molecules to a better vitality state, after which they drop to their floor state whereas emitting infrared mild at a attribute wavelength of 1.2 THz.


Ü. Kavak, F. F. S. van der Tak, A. G. G. M. Tielens and R. F. Shipman, ‘Origin of hydrogen fluoride emission in the Orion Bar,’ Astronomy & Astrophysics


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