Herschel links star formation to sonic booms

April 13, 2011
Dense filaments of gas in the IC5146 interstellar cloud. This image was taken by ESA’s Herschel space observatory at infrared wavelengths 70, 250 and 500 microns. Stars are forming along these filaments. Credit: ESA/Herschel/SPIRE/PACS/D. Arzoumanian (CEA Saclay) for the “Gould Belt survey” Key Programme Consortium.

(PhysOrg.com) -- 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.

The filaments are huge, stretching for tens of light years through space and has shown that newly-born stars are often found in the densest parts of them. One filament imaged by Herschel in the Aquila region contains a cluster of about 100 infant stars.

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.

"This is a very big surprise," says Doris Arzoumanian, Laboratoire AIM Paris-Saclay, CEA/IRFU, the lead author on the paper describing this work. Together with Philippe André from the same institute and other colleagues, she analysed 90 filaments and found they were all about 0.3 light years across, or about 20 000 times the distance of Earth from the Sun. This consistency of the widths demands an explanation.

Herschel links star formation to sonic booms
The network of interstellar filaments in Polaris as imaged by ESA’s Herschel space observatory at infrared wavelengths 250, 350 and 500 microns. These filaments are not yet forming stars. Credits: ESA/Herschel/SPIRE/Ph. André (CEA Saclay) for the Gould Belt survey Key Programme Consortium and A. Abergel (IAS Orsay) for the Evolution of Interstellar Dust Key Programme Consortium.

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.

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.

"This is not direct proof, but it is strong evidence for a connection between interstellar turbulence and filaments. It provides a very strong constraint on theories of star formation," says Dr André.

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.

Explore further: Herschel views deep-space pearls on a cosmic string

Related Stories

Herschel views deep-space pearls on a cosmic string

October 2, 2009

(PhysOrg.com) -- Herschel has delivered spectacular vistas of cold gas clouds lying near the plane of the Milky Way, revealing intense, unexpected activity. The dark, cool region is dotted with stellar factories, like pearls ...

Inside the dark heart of the Eagle

December 16, 2009

(PhysOrg.com) -- Herschel has peered inside an unseen stellar nursery and revealed surprising amounts of activity. Some 700 newly-forming stars are estimated to be crowded into filaments of dust stretching through the image. ...

Planck sees tapestry of cold dust (w/ Video)

March 17, 2010

(PhysOrg.com) -- 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 ...

Herschel finds a hole in space

May 11, 2010

(PhysOrg.com) -- ESA's Herschel infrared space telescope has made an unexpected discovery: a hole in space. The hole has provided astronomers with a surprising glimpse into the end of the star-forming process.

Herschel reveals the hidden side of star birth

May 6, 2010

The first scientific results from ESA's Herschel infrared space observatory are revealing previously hidden details of star formation. New images show thousands of distant galaxies furiously building stars and beautiful star-forming ...

Baby stars in the Rosette cloud

April 12, 2010

Herschel's latest image reveals the formation of previously unseen large stars, each one up to ten times the mass of our Sun. These are the stars that will influence where and how the next generation of stars are formed. ...

Recommended for you

More than 15,000 near-Earth objects and counting

October 28, 2016

The international effort to find, confirm and catalogue the multitude of asteroids that pose a threat to our planet has reached a milestone: 15 000 discovered – with many more to go.

How planets like Jupiter form

October 28, 2016

Young giant planets are born from gas and dust. Researchers of ETH Zürich and the Universities of Zürich and Bern simulated different scenarios relying on the computing power of the Swiss National Supercomputing Centre ...


Adjust slider to filter visible comments by rank

Display comments: newest first

1 / 5 (1) Apr 14, 2011
Thanks for publishing this interesting report.

It is indeed surprising to see "stars forming like beads on strings in some of these filaments," if that is the correct conclusion from the observations.
not rated yet Apr 15, 2011
I forget which documentary or 'history of the universe' type show I was watching, but it had an illustration of how gravity interacted in (one theory of) the early universe. It had an infinite array of equidistant balls bound by gravity. Once one was removed, it disrupted the equilibrium that was present (due to gravity drawing the balls together) and the resultant pattern in the mid-term was a kind of 'stranding' of the balls. They formed conduits which gathered the balls as the disruption moved it's way from the 'removed' ball.

Reading this summary reminded me of that example - the shock wave being the disruption of an otherwise relatively stable system.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.