A network of interstellar filaments in Polaris

Interstellar filaments in Polaris (Image ESA and the SPIRE & PACS consortia, Ph. André (CEA Saclay) for the Gould’s Belt Survey Key Programme Consortium, and A. Abergel (IAS Orsay) for the Evolution of Interstellar Dust Key Programme Consortium)
Interstellar filaments in Polaris (Image ESA and the SPIRE & PACS consortia, Ph. André (CEA Saclay) for the Gould’s Belt Survey Key Programme Consortium, and A. Abergel (IAS Orsay) for the Evolution of Interstellar Dust Key Programme Consortium)

ESA has published a new picture of the network of interstellar filaments seen by the Herschel Space Observatory in the space around Polaris, the North Star, which is actually a multiple system. For this reason also known as Polaris Flare, it’s an interstellar cloud in which filaments formed in which there are gas and dust visible especially at infrareds.

This region of space, that is nearly 500 light years from Earth, stretches for tens of light years and its twisted interstellar filaments could be a situation that precedes the beginning of star formation in the densest areas. What the astronomers can see at the moment doesn’t seem enough to generate enough gas concentrations to trigger the birth of a star yet so they still can’t figure out if that will be the future development.

The Herschel Space Observatory was named after the astronomer William Herschel, who among other things discovered the most distant companion of the red supergiant present in the Polaris system. Therefore it seems appropriate that the instrument has been used to observe that area of ​​space.

Already in 2011, ESA had produced the first images captured at infrareds using the SPIRE (Spectral and Photometric Imaging Receiver) instrument at wavelengths of 250, 300 and 500 microns. Now those images have been reworked to create this new color composite.

Astronomers conducted computer simulations to try to understand the formation of interstellar filaments. The most likely explanation is that slow shock waves dissipated in the interstellar clouds after being produced by supernovae and traveled across the galaxy, sweeping gas and dust that ended up forming the thick filaments we see today.

The temperature of interstellar clouds is very low, around 10 Kelvin, so the speed of sound is much lower than at sea level on Earth. The consequence is that the slow shockwaves are the interstellar equivalent of sonic booms. Losing energy in the clouds, they leave behind tenuous filaments of gas and dust.

In recent years, that area of ​​space was also observe with the Planck Surveyor, which can be considered the Herschel Space Observatory’s sibling because the two of them were launched together on May 14, 2009 on the same Ariane 5 ECA rocket. Since the Planck has instruments completely different from Herschel’s, the result obtained by putting together the data gathered is too.

The map of the magnetic field of the Milky Way focused on the polarized light emitted by interstellar dust created using data collected by the Planck Surveyor has the look of a painting by vincent Van Gogh. The area called Polaris Flare is a part of that map and has the same appearance.

These images provide a series of information on that area but they’re still not enough to predict the future evolution of those filaments and especially of the major gas concentrations. It may take millions of years before a few stars start forming, if it will ever happen.

Magnetic field in Polaris Flare (Image ESA and the Planck Collaboration)
Magnetic field in Polaris Flare (Image ESA and the Planck Collaboration)

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