Saturday, May 30, 2015

Threading the Milky Way

The G49 filament seen by ESA’s Herschel space observatory. With a total mass over 80 000 solar masses, this huge but slender structure of gas and dust extends over about 280 light-years in length, while its diameter is only about 5 light-years.  Cooler gas and dust is seen in red and yellow, with temperatures as low as –252ºC. In the densest and coolest clumps, the seeds of new generations of stars are taking shape. A brighter clump of matter is visible at the left tip of the wispy thread. This filament is about 18 000 light-years away.  The image is a composite of the wavelengths of 70 microns (blue), 160 microns (green) and 350 microns (red) and spans about 1.17x0.93º. The image is oriented with northeast towards the left of the image and southwest towards the right. Credit: ESA/Herschel/PACS/SPIRE/Ke Wang et al. 2015

New images of huge filamentary structures of gas and dust from ESA’s Herschel space observatory reveal how matter is distributed across our Galaxy, the Milky Way. Long and flimsy threads emerge from a twisted mix of material, taking on complex shapes as the gas and dust in them become denser and cooler. Two of them even exhibit a ‘head’ – a brighter clump of matter at the tip of the wispy thread. The image above shows a filament called G49, which contains 80,000 suns' worth of mass. This huge but slender structure of gas and dust extends about 280 light-years in length, while its diameter is only about 5 light-years across. The filament is about 18,000 light-years away.

“The greatest surprise was the ubiquity of filaments in these nearby clouds and their intimate connection with star formation,” explains Philippe André from CEA/IRFU, France, Principal Investigator for the Herschel Gould Belt Survey. “But there is more: these observations revealed that filaments, which may extend to several light-years in length, appear to have a universal width of about one third of a light year. This suggests that something fundamental is lurking underneath.”

With masses of thousands to several tens of thousands times that of our Sun, these are among the most prominent filaments ever observed in the Galaxy. Longer than 100 light-years, they are at most 10 light-years wide, reproducing even at these very large scales the filamentary distribution of matter that Herschel has observed in detail in nearby star-forming regions in the Milky Way.

The G47 filament seen by ESA’s Herschel space observatory. With a total mass of about 20 000 solar masses, this huge but slender structure of gas and dust extends over about 250 light-years in length, while its diameter is only about 10 light-years.  A winding thread of cooler gas and dust is seen in red and yellow, with temperatures as low as –256ºC. In the densest and coolest clumps, the seeds of new generations of stars are taking shape. This filament is about 14 000 light-years away.  The image is a composite of the wavelengths of 70 microns (blue), 160 microns (green) and 350 microns (red) and spans about 0.68x0.50º. The image is oriented with northeast towards the left of the image and southwest towards the right. Credit: ESA/Herschel/PACS/SPIRE/Ke Wang et al. 2015
The G47 filament seen by ESA’s Herschel space observatory. With a total mass of about 20 000 solar masses, this huge but slender structure of gas and dust extends over about 250 light-years in length, while its diameter is only about 10 light-years. A winding thread of cooler gas and dust is seen in red and yellow, with temperatures as low as –256ºC. In the densest and coolest clumps, the seeds of new generations of stars are taking shape. This filament is about 14 000 light-years away. The image is a composite of the wavelengths of 70 microns (blue), 160 microns (green) and 350 microns (red) and spans about 0.68x0.50º. The image is oriented with northeast towards the left of the image and southwest towards the right. Credit: ESA/Herschel/PACS/SPIRE/Ke Wang et al. 2015

While dust is only a minor ingredient in this cosmic blend, it shines brightly at the far-infrared and submillimetre wavelengths probed by Herschel. This allowed astronomers to reveal for the first time the coolest and densest portions in this tangle, visible in red and yellow in these false-colour images.

The filaments are dotted with brighter clumps: these are cosmic incubators, where the seeds of new generations of stars are taking shape. The blue and violet glow of the fuzzy splotches that embellish the filaments reveals pockets of warmer material, set ablaze by the fierce radiation released by newborn stars still embedded within them.

The G64 filament seen by ESA’s Herschel space observatory. With a total mass of about 5000 solar masses, this huge but slender structure of gas and dust extends over about 170 light-years in length, while its diameter is only about 9 light-years.  Cooler gas and dust is seen in red and yellow, with temperatures as low as –256ºC. In the densest and coolest clumps, the seeds of new generations of stars are taking shape. A brighter clump of matter is visible at the right tip of the wispy thread. This filament is about 12 000 light-years away.  The image is a composite of the wavelengths of 70 microns (blue), 160 microns (green) and 350 microns (red) and spans about 0.66x0.40º. The image is oriented with northeast towards the left of the image and southwest towards the right. Credit: ESA/Herschel/PACS/SPIRE/Ke Wang et al. 2015
The G64 filament seen by ESA’s Herschel space observatory. With a total mass of about 5000 solar masses, this huge but slender structure of gas and dust extends over about 170 light-years in length, while its diameter is only about 9 light-years. Cooler gas and dust is seen in red and yellow, with temperatures as low as –256ºC. In the densest and coolest clumps, the seeds of new generations of stars are taking shape. A brighter clump of matter is visible at the right tip of the wispy thread. This filament is about 12 000 light-years away. The image is a composite of the wavelengths of 70 microns (blue), 160 microns (green) and 350 microns (red) and spans about 0.66x0.40º. The image is oriented with northeast towards the left of the image and southwest towards the right. Credit: ESA/Herschel/PACS/SPIRE/Ke Wang et al. 2015

Before Herschel, only two gigantic filaments like these were known, but astronomers have now used data from the observatory to uncover several new ones weaving their way through the spiral arms of the Milky Way. They believe that these are the first structures to form as interstellar matter starts coming together, eventually leading to the formation of stars.

“The intricate distribution of filaments in the interstellar medium revealed by Herschel has definitely revolutionised our view of how stars form in the Milky Way and, presumably, also in other similar galaxies,” comments Göran Pilbratt, ESA Herschel Project Scientist. “An increasingly coherent picture is now emerging from combining the analysis of these data with predictions from theory and numerical simulations, as astronomers continue to study the physical processes underlying the fascinating origin of stars and planets.”

Herschel is a European Space Agency mission, with science instruments provided by consortia of European institutes and with important participation by NASA. While the observatory stopped making science observations in April 2013, after running out of liquid coolant as expected, scientists continue to analyze its data.

Credit: ESA

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