Credits: ESA/Herschel/SPIRE/PACS/D. Arzoumanian (CEA Saclay) for the “Gould Belt survey” Key Programme Consortium. HI-RES JPEG (Size: 757 kb) - HI-RES TIFF (Size: 14 736 kb)
ESA’s Herschel space observatory has revealed that nearby interstellar clouds contain networks of tangled gaseous filaments. Intriguingly, each filament is approximately the same width, hinting that they may result from interstellar sonic booms throughout our Galaxy.
Such filaments in interstellar clouds have been glimpsed before by other infrared satellites, but they have never been seen clearly enough to have their widths measured. Now, Herschel has shown that, regardless of the length or density of a filament, the width is always roughly the same.
Comparing the observations with computer models, the astronomers concluded that filaments are probably formed when slow shockwaves dissipate in the interstellar clouds. These shockwaves are mildly supersonic and are a result of the copious amounts of turbulent energy injected into interstellar space by exploding stars. They travel through the dilute sea of gas found in the Galaxy, compressing and sweeping it up into dense filaments as they go.
Interstellar clouds are usually extremely cold, about 10 degrees Kelvin above absolute zero, and this makes the speed of sound in them relatively slow at just 0.2 km/s, as opposed to 0.34 km/s in Earth’s atmosphere at sea-level.
These slow shockwaves are the interstellar equivalent of sonic booms. The team suggests that as the sonic booms travel through the clouds, they lose energy and, where they finally dissipate, they leave these filaments of compressed material.
The team made the connection by studying three nearby clouds, known as IC5146, Aquila, and Polaris, using Herschel’s SPIRE and PACS instruments.
“The connection between these filaments and star formation used to be unclear, but now thanks to Herschel, we can actually see stars forming like beads on strings in some of these filaments,” says Göran Pilbratt, the ESA Herschel Project Scientist.
Contact for further information
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