Herschel's hunt for filaments in the Milky Way

May 29, 2015, European Space Agency
The Orion A Molecular Cloud. Credit: ESA/Herschel/Ph. André, D. Polychroni, A. Roy, V. Könyves, N. Schneider for the Gould Belt survey Key Programme

Observations with ESA's Herschel space observatory have revealed that our Galaxy is threaded with filamentary structures on every length scale. From nearby clouds hosting tangles of filaments a few light-years long to gigantic structures stretching hundreds of light-years across the Milky Way's spiral arms, they appear to be truly ubiquitous. The Herschel data have rekindled the interest of astronomers in studying filaments, emphasising the crucial role of these structures in the process of star formation.

Stars are born in the densest pockets of the interstellar medium, a diffuse mixture of gas and dust that pervades galaxies, including our Milky Way. One of the most intriguing questions in astrophysics concerns understanding how this material, which is typically characterised by very low density, can come together, creating denser concentrations that later evolve into compact cores and, finally, give birth to .

In the search for answers, astronomers observe giant molecular clouds, the cosmic incubators where gas and dust are transformed into stars. While these studies are performed using a variety of techniques, one crucial approach is the observation of infrared light, since the shines brightly at these long wavelengths.

In this context, ESA's Herschel space observatory has been a true game changer. Probing the portion of the electromagnetic spectrum that ranges from the far-infrared to sub-millimetre wavelengths, it has collected unprecedented data during its three and a half years of observing. One of the key aspects that emerged from these observations is the presence of a filamentary network nearly everywhere in our Galaxy's interstellar medium. The picture that is emerging is that these structures are closely linked to the formation of stars.

Prior to Herschel, astronomers had already identified several filaments in interstellar clouds and recognised their potential importance for . However, only with the increased sensitivity and spatial resolution granted by this observatory, combined with its large-scale surveys, could they reveal the full extent of filamentary patterns in the Milky Way.

One of the surveys performed with Herschel – the Gould Belt Survey – focussed on a giant ring of star-forming regions, all located no more than 1500 light-years away from the Sun. The vicinity of these clouds allowed astronomers to obtain exceptionally detailed images using Herschel, unearthing intricate webs of filaments in each region that they examined.

"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."

The astronomers are still trying to understand the details of the star formation processes taking place in these clouds, aided by the abundance and variety of data collected with Herschel.

Herschel's hunt for filaments in the Milky Way
The Polaris Flare. Credit: ESA/Herschel/SPIRE/Ph. André for the "Gould Belt survey" Key Programme Consortium and A. Abergel for the "Evolution of Interstellar Dust" Key Programme Consortium

While most filaments are dotted with compact cores, suggesting that stars are readily taking shape in these dense 'fibres' of the interstellar medium, there are also regions that exhibit complex tangles of filaments but no signs of on-going star formation. A study of the most spectacular example of this phenomenon, the Polaris Flare, indicates that filaments must somehow precede the onset of star formation.

The scenario that has emerged from the new Herschel data suggests that star formation proceeds in two steps: first, turbulent motions of the interstellar gas and dust create an intricate web of filamentary structures; then, gravity takes over, causing only the densest filaments to contract and fragment, eventually leading to the formation of stars.

Indeed, the universal width of filaments seems to correspond, at least in the nearby clouds of the Gould Belt Survey, to the scale at which interstellar material undergoes the transition from supersonic to subsonic state.

In addition, the material along filaments is not at all static: astronomers have detected what appear to be accretion flows, with the most prominent filaments drawing matter from their surroundings through a network of smaller filaments. A striking example of such processes is seen in the Taurus Molecular Cloud, where the B211/B213 filament exhibits a series of so-called 'striations' perpendicular to the main filament.

This pattern is very similar to that predicted from numerical simulations that model the process of star formation in molecular clouds. According to these simulations, interstellar material flows towards dense filaments along routes that are parallel to the direction of the local magnetic field, as was observed, so the new data indicate the importance of interstellar magnetic fields in shaping these structures.

Herschel's hunt for filaments in the Milky Way
The B211/B213 filament in the Taurus Molecular Cloud. Credit: ESA/Herschel/PACS, SPIRE/Gould Belt survey Key Programme/Palmeirim et al. 2013

However, star formation does not appear to take place only in filaments. While these structures seem to be the preferred sites for stellar birth, the extraordinary data from Herschel confirmed that a small fraction of stars may also form far away from dense filaments.

In particular, a detailed study of the L1641 molecular clouds in the Orion A complex suggests that star formation along filaments is the preferential channel to produce typical solar-type stars, while stars that are born away from these dense, elongated structures tend to have lower masses. This dichotomy could be a result of the greater availability of raw material to protostars that are forming on a filament compared to those that take shape in less dense environments.

Another of Herschel's key findings is that the presence and abundance of filaments are not limited to our immediate neighbourhood. In fact, these structures appear everywhere also in the Herschel infrared Galactic Plane Survey (Hi-GAL), which scanned the distribution of the interstellar medium in the huge disc – about 100 000 light-years across – where most of the Milky Way's stars form and reside.

"We detected a wealth of huge filaments, with lengths ranging from a few to a hundred light-years, revealing what seems to be the 'skeleton' of our Galaxy," explains Sergio Molinari from IAPS/INAF, Italy, Principal Investigator for the Hi-GAL Project.

Herschel's hunt for filaments in the Milky Way
The filamentary structure of the Galactic Plane. Credit: ESA/PACS & SPIRE Consortium, S. Molinari, Hi-GAL Project
"While it is possible that these structures arose from different physical processes than those giving rise to the small-scale filaments observed in the Sun's vicinity, the omnipresent aspect of filamentary structures in the Milky Way is beyond doubt."

In the post-Herschel era, one thing is certain: filaments play a leading role in the build-up of galactic material, creating favourable hubs for the formation of stars. This is likely a hierarchical process, starting on very large scales and propagating onwards, to smaller and smaller scales, funnelling interstellar gas and dust into increasingly denser concentrations and thus fostering stellar birth across the Galaxy.

Large-scale filaments fragmenting into compact cores that later evolve into stars have been detected all across the Galactic Plane, even in its outermost, peripheral regions. As filaments grow more massive, the material within them contracts and forms smaller structures, preserving the filamentary pattern on all length scales.

Herschel's hunt for filaments in the Milky Way
Filaments in outer regions of the Galactic Plane. Credit: ESA/Herschel/PACS, SPIRE/Hi-GAL Project/Schisano et al. 2014

Further investigation of the Hi-GAL survey has revealed new and even more prominent filaments, extending over hundreds of light-years and weaving their way through the spiral arms of the Milky Way. The study revealed nine filaments in some very dense, inner regions of the Galactic Plane, detecting these for the first time through the direct emission of dust within them, allowing an accurate determination of their mass, size and physical characteristics. Astronomers believe that almost a hundred similar, gigantic structures are still hiding in the data.

"The intricate distribution of in the 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."

Explore further: Image: Glowing jewels in the galactic plane

More information: RELATED PUBLICATIONS:

Ph. André et al. 2010, Astronomy & Astrophysics, 518, L102
S. Molinari et al. 2010, Astronomy & Astrophysics, 518, L100
D. Arzoumanian et al. 2011, Astronomy & Astrophysics, 529, L6
D. Polychroni et al. 2013, Astrophysical Journal Letters, 777, L33
P. Palmeirim et al. 2013, Astronomy & Astrophysics, 550, A38
D. Arzoumanian et al. 2013, Astronomy & Astrophysics, 553, A119
Ph. André et al. 2014, in Protostars and Planets VI, p. 27
D. Elia et al. 2013, Astrophysical Journal, 772, 45
E. Schisano et al. 2014, Astrophysical Journal, 791, 27
K. Wang et al. 2015, Monthly Notices of the Royal Astronomical Society, 450, 4043

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cantdrive85
1.8 / 5 (10) May 29, 2015
Observations with ESA's Herschel space observatory have revealed that our Galaxy is threaded with filamentary structures on every length scale. From nearby clouds hosting tangles of filaments a few light-years long to gigantic structures stretching hundreds of light-years across the Milky Way's spiral arms, they appear to be truly ubiquitous.


I think I've heard this before...Oh right, that is a foundational tenet of Plasma Cosmology!
rossim22
1.9 / 5 (13) May 29, 2015
I'm seriously beginning to question the rationality of these scientists. They found that the "gas and dust" (NOT frickin gas, they're ionized a.k.a. a plasma) form filaments first and stars second. So how do the filaments form? They suggest turbulence! Are you serious? Random motions in a vacuum apparently form long, uniformly wide filaments. "Then, gravity takes over, causing only the densest filaments to contract and fragment, eventually leading to the formation of stars." Where the hell was gravity to begin with? Why did it choose only to be effective after the filaments were constructed? Maybe a non-random process forms the filaments and, thus, the stars.

Don't you all see the pattern? These things must exist in a plasma cosmology paradigm, yet they're considered random events in the standard model. Plasma scalability is common knowledge, with experimental evidence. The same filamentary structures in a child's plasma ball are the same that span the universe.
Benni
1.6 / 5 (7) May 29, 2015
Interesting that there was no reference to Dark Matter as being the underlying feature in their references to gravity.
barakn
5 / 5 (6) May 29, 2015
If the dark matter distribution was smooth at the scale of a filament, it would have little effect.
vidyunmaya
2 / 5 (8) May 29, 2015
Many thanks for the data. astronomy trying to catch-up with Plasma Cosmology studies.
My books have many projections that help universe modeling and these filamentary nature is covered under cosmic Flows ;1.PLASMA VISION OF THE UNIVERSE-1993: TXU 729718 2.THE VISION OF COSMIC TO *PREM UNIVERSE-1995 -: TXU 893693 )*PREM: Plasma Regulated Electro-Magnetic Universe .[vidyardhi nanduri]
Today one can say " plasma regulated Electromagnetic phenomena under magnetic field environment"
is coming out to be real
VCRAGAIN
1.8 / 5 (10) May 29, 2015
SO HAPPY TO SEE ALL THE PLASMA COMMENTS !
Yes they are finally, finally coming around to the truth of it all - we are seeing the glorious filaments of plasma EVERYWHERE - now what was that rubbish about dark* something - all that hangs on the Redshift theory which is also debunked way back - so guys - just give it up - your math is NOT needed to understand what you can see for yourselves in all it's gorgeous glory - the stars are all floating in giant seas of plasma, and Electricity is manifested everywhere, from the smallest physical structure to the largest we can see - all is Electrical phenomena - including ourselves !
Benni
1.7 / 5 (11) May 30, 2015
If the dark matter distribution was smooth at the scale of a filament, it would have little effect.


......but according to the DM Narrative, 90% of the Universe is missing. The problem with this kind of Funny Farm Science is that they have yet to make an actual measurement of gravity fields that exceeds the quantity of Visible Matter by the ratio they claim: DM /VM =90%/10%= 9.

So, if DM is 90% of total mass of the universe & VM is a mere 10%, how does it compute that a mere fraction of the bodies of the universe (Speaking of Rotation Curves of Spiral Galaxies) do not appear to comport with the Einstein Field Equations & Newtonian Gravity?

Odd isn't it, that everytime we apply newer viewing & measurement technology to our repertoire of scientific instrumentation, the more evident it becomes that here is a lot more VM mass within the arms of Spiral Galaxies than we imagined.......but, the Cosmic Fairy Dust crowd loves their theism of DM & undetectable gravity.
jposterman
5 / 5 (3) May 30, 2015
We are all made of the stars.
digitaltrails
not rated yet Jun 01, 2015
It looks like 3D streams and rivers, stuff flowing into the valleys.
bohemianexile
1 / 5 (7) Jun 01, 2015
This is more evidence supporting Electric Universe theory. They have been talking about filamentary structures and their role in star formation for quite a while now. Not acknowledging the people that have consistently predicted every major astronomical observation of the past 10 years or more is becoming criminal instead of just comical.
Vietvet
4.8 / 5 (6) Jun 01, 2015
This is more evidence supporting Electric Universe theory. They have been talking about filamentary structures and their role in star formation for quite a while now. Not acknowledging the people that have consistently predicted every major astronomical observation of the past 10 years or more is becoming criminal instead of just comical.


LMFAO!
Stevepidge
1 / 5 (3) Jun 10, 2015
@bohemianexile: You do realize, don't you, that there is no "Electric Universe theory"? Certainly nothing which has been published, nothing which meets any reasonable criteria for being scientific, nothing which can be used to objectively and independently derive predictions, ...

Who are "the people that have consistently predicted every major astronomical observation of the past 10 years or more"? They are certainly not the three or four living (self-styled) "electrical theorists"!


Who understands the real world application of throwing a baseball as a major league pitcher better, the world's best pitcher or the world's best Newtonian physicist? In the answer lies the secrets to the universe and of life itself.
Captain Stumpy
5 / 5 (3) Jun 10, 2015
Who understands the real world application of throwing a baseball as a major league pitcher better, the world's best pitcher or the world's best Newtonian physicist?
@stevepig
that really is going to depend on what they are trying to do in this "real world application"...

if all you want is a strike over home plate and tell kids about why they're are special, then you ask the pitcher

if you want to describe the motion, speed, mass, impact on a glove or bat, or any of the other myriad details so that you can come to an understanding of the physics for better understanding of the real world, gravity, reality and more... you would ask a physicist

Our physics classes had baseball in the tests...
i don't know too many baseball pitchers who know anything about the physics, though
(kinda sad, when you think about it)
Stevepidge
1 / 5 (3) Jun 10, 2015
I said application. The act and results of throwing a baseball. Not the maths involved. Science at least theoretical sciences do not possess understanding of nature only a crude representation of it. The pitcher experiences throwing the ball with an intimate knowledge that is beyond math. Experience is not something that can be quantified mathematically or with models. It is a sub conscious action that requires no math, only pure understanding based on experience.
Captain Stumpy
5 / 5 (2) Jun 11, 2015
I said application
@Steve
you also said
Who understands..
so, what you really meant was who understands the experience?What?
The pitcher experiences throwing the ball with an intimate knowledge that is beyond math
no... again, the pitcher might be able to intuitively know where that ball will go, but that does NOT mean he "understands" what is happening
there is a real difference there
that is the reason i brought that up

for instance:
i can see what happened on a crime scene... blood spatter, bruising, signs of defense, wound entry points, tracks, and much more...
but to "understand and explain" what happened, i would still need to use the physics and math...and that would mean recreating the scene and attack as well as wounds

again, that is the power of the scientific method

so understanding is NOT always intuitive
Captain Stumpy
5 / 5 (1) Jun 11, 2015
You've lost me I'm afraid
@JeanTate
Steve is a little fuzzy on clarity most of the time... like above: he states
Who understands the real world application of throwing a baseball as a major league pitcher better, the world's best pitcher or the world's best Newtonian physicist?
he actually MEANT to say, as he notes
I said application. The act and results of throwing a baseball
this means he was actually trying to say: who can throw a ball better or who knows/understands how to throw the ball (either one - still not perfectly clear, IMHO)

of course, that is completely irrelevant to the topic, and also not what he specifically stated

this is at best a distraction and an attempt to utilize philosophy in science

i don't think he will be able to clarify it more
Stevepidge
1 / 5 (3) Jun 11, 2015
I'm saying the applied knowledge of actually throwing a baseball is not an act of the conscious mind. Understanding is ultimately the act of doing. While doing is not synonymous with reasoning or the conscious mind. You could use concert pianists as an example if you wish. The subject of the analogy is irrelevant. Likewise the understanding of the universe is intrinsically understood by the subconscious, it is only the conscious mind that obfuscates things by trying to quantify understanding as some kind of concrete transmittable information. Science will always observe reality as an obfuscation, an effervescent and vibrant mirage that disappears the closer one gets to discern the finer details of nature. Understanding does not require effort as how can you learn something you already know?
"Be the ball" as quoted by Chevy Chase in Caddy Shack.
Captain Stumpy
5 / 5 (2) Jun 11, 2015
I'm saying the applied knowledge of actually throwing a baseball is not an act of the conscious mind
@Steve
thanks for the clarification, but you are wrong about
Understanding is ultimately the act of doing
i understand how to use a computer and the basics of the internet, HTTP, IP's, and more
but that doesn't make me a hacker nor does it explain QM making me a physicist

It doesn't mean i "understand" QM nor the foundations of the technology which have given us computers, cell phones, GPS, satellites, communication, etc
You could use concert pianists as an example if you wish
ok, lets examine that one!

a concert pianist knows how to play the piano, but that does NOT guarantee they understand the physics behind transmission of sound, how vibrations travel through different media, WHY the piano makes the sound it does nor the mathematics behind the music etc

do you get the point yet?
cont'd
Captain Stumpy
5 / 5 (2) Jun 11, 2015
@steve
Science will always observe reality as an obfuscation, an effervescent and vibrant mirage that disappears the closer one gets to discern the finer details of nature. Understanding does not require effort as how can you learn something you already know?
"Be the ball" as quoted by Chevy Chase in Caddy Shack
and as i stated, this does NOT mean you understand ANYTHING...

your argument stems from philosophy
Philosophy is highly subjective

knowing details is NOT obfuscation
it is the reason we can perform surgery and heal bacterial infections instead of using pyramiding or simply "praying away" the disease

it is the reason we can use GPS or how we found out about Polio vaccines

"detail is THE key to understanding -
you get the little things right and the big stuff falls into order"
SMSgt Mark Palm KMSFD

"don't just look at the big picture- the details are what will kill you if you ignore them"
GM-13 George Shackett, Fire Chief, KMCFD

(Trumps caddy shack)

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