“Tendrils of the coldest stuff in our galaxy”

ESA’s cool infrared Herschel observatory sent its first images back in October last year, just after its launch companion, the even cooler Planck observatory achieved first light. Both are twittering away – Planck and Herschel. But as the BBC notes Planck scientists have now released “a snapshot of the colossal swathes of cold dust that spread through the Milky Way galaxy.”

Wednesday’s pictures come from Planck’s highest frequency channels and cover about 10% of the sky. They show the great filaments of dust within about 500 light-years of Earth. In the wavelengths it is working, Planck is well tuned to see cold matter. Some of the dust it detects is about minus 261C (12K). “We have the ability to look at very cold emission, essentially dust. We can do unbiased searches over the whole sky for these regions that are very important because they are where stars are forming,” Dr Tauber explained.

Nasa chips in here. And provides the wider view. Image credit: ESA and the HFI Consortium, IRAS.

But it’s really ESA’s gig.

“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.