Giant filaments of cold dust stretching through our Galaxy are revealed in a new image from ESA’s Planck satellite. Analysing these structures could help to determine the forces that shape our Galaxy and trigger star formation.
The image spans about 50° of the sky. It is a three-colour combination constructed from Planck’s two highest frequency channels (557 and 857 GHz, corresponding to wavelengths of 540 and 350 micrometres), and an image at the shorter wavelength of 100 micrometres made by the IRAS satellite. This combination visualises dust temperature very effectively: red corresponds to temperatures as cold as 10° above absolute zero, and white to those of a few tens of degrees. Overall, the image shows local dust structures within 500 light-years of the Sun - Credit: ESA/HFI Consortium/IRAS
The image shows the filamentary structure of dust in the solar neighborhood – within about 500 light-years of the Sun. The local filaments are connected to the Milky Way, which is the pink horizontal feature near the bottom of the image.
“What makes these structures have these particular shapes is not well understood,” says Jan Tauber, ESA Project Scientist for Planck. The denser parts are called molecular clouds while the more diffuse parts are ‘cirrus’. They consist of both dust and gas, although the gas does not show up directly in this image.
There are many forces at work in the Galaxy to help shape the molecular clouds and cirrus into these filamentary patterns. For example, on large scales the Galaxy rotates, creating spiral patterns of stars, dust, and gas. Gravity exerts an important influence, pulling on the dust and gas. Radiation and particle jets from stars push the dust and gas around, and magnetic fields also play a role, although to what extent is presently unclear.
Bright spots in the image are dense clumps of matter where star formation may take place. As the clumps shrink, they become denser and better at shielding their interiors from light and other radiation. This allows them to cool more easily and collapse faster.
ESA’s Herschel space telescope can be used to study such regions in detail, but only Planck can find them all over the sky. Launched together in May 2009, Planck and Herschel are both studying the coolest components of the Universe. Planck looks at large structures, while Herschel can make detailed observations of smaller structures, such as nearby star-forming regions.
For latest updates from the Herschel/Planck mission follow ESAHerschel and HerschelPlanck on twitter.