APOD: Stardust in Aries (2017 Dec 09)

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Expand view Topic review: APOD: Stardust in Aries (2017 Dec 09)

Re: APOD: Stardust in Aries (2017 Dec 09)

by Fred the Cat » Sun Dec 31, 2017 4:28 pm

I’d never heard of vacuum welding before. It makes you think that it might be a consideration when hypothesizing accretion models. :?:

Re: APOD: Stardust in Aries (2017 Dec 09)

by Chris Peterson » Sun Dec 31, 2017 3:25 pm

Ann wrote:Much of the dusty region appears relatively turbulent. To my amateur mind, it seems reasonable that turbulence should rearrange the distribution of dust and gas, making it more concentrated in some places and less so in others.
I wasn't suggesting we don't end up with an inhomogeneous density distribution. The densities is such regions vary over many orders of magnitude. Only that I don't think the dust accounts for more than a few percent of the total mass even in the dustiest regions. Almost all the mass is hydrogen and helium. (Nor does that mean the dust isn't important, as it appears to provide some sort of catalytic function when it comes to condensing regions.)

Re: APOD: Stardust in Aries (2017 Dec 09)

by Ann » Sun Dec 31, 2017 7:40 am

Chris Peterson wrote:
distefanom wrote:Maybe also the interstellar medium "wind", acted from nearby already formed stars could shape also, those dust clouds.
It seems to me that large clumps of interstellar stuff behaves differently when it comes in such large quantities...
Also the simple and also very well known "terrestial dust" forms and behaves differently when it is formed in space.

http://physicsworld.com/cws/article/new ... imulations
It's also important to keep in mind that in most such regions dust only accounts for a small fraction of the total mass- most of which is present as hydrogen and helium.
But it is clear that dust is also present. And it is clear that this dust - and therefore presumably also the concentration of hydrogen and helium - is unevenly distributed. Most of the dust curtains look flimsy, but there are little spots that are very dark, as if they had become impenetrable to optical light due to the concentration of dust.

Much of the dusty region appears relatively turbulent. To my amateur mind, it seems reasonable that turbulence should rearrange the distribution of dust and gas, making it more concentrated in some places and less so in others.

Ann

Re: APOD: Stardust in Aries (2017 Dec 09)

by bystander » Sun Dec 31, 2017 7:23 am

Sally's departure from the APOD discussion has been split from this topic and moved to the Café.

Re: APOD: Stardust in Aries (2017 Dec 09)

by distefanom » Sun Dec 10, 2017 3:20 pm

What's the general rule astronomers uses for evaluating the mass of such gas clouds in space? In which way they estimate the cloud density so they can infer it's total mass? I can imagine that densities varies largely from place to place, also around entire galaxies... It seems to me a mystery how do they do it. I would like to know!

Re: APOD: Stardust in Aries (2017 Dec 09)

by Chris Peterson » Sat Dec 09, 2017 11:54 pm

distefanom wrote:Maybe also the interstellar medium "wind", acted from nearby already formed stars could shape also, those dust clouds.
It seems to me that large clumps of interstellar stuff behaves differently when it comes in such large quantities...
Also the simple and also very well known "terrestial dust" forms and behaves differently when it is formed in space.

http://physicsworld.com/cws/article/new ... imulations
It's also important to keep in mind that in most such regions dust only accounts for a small fraction of the total mass- most of which is present as hydrogen and helium.

Re: APOD: Stardust in Aries (2017 Dec 09)

by distefanom » Sat Dec 09, 2017 10:32 pm

Maybe also the interstellar medium "wind", acted from nearby already formed stars could shape also, those dust clouds.
It seems to me that large clumps of interstellar stuff behaves differently when it comes in such large quantities...
Also the simple and also very well known "terrestial dust" forms and behaves differently when it is formed in space.

http://physicsworld.com/cws/article/new ... imulations


Anyway Thanks Chris ;-)

Re: APOD: Stardust in Aries (2017 Dec 09)

by Ann » Sat Dec 09, 2017 9:03 pm

My sense of pareidolia makes me see a man lying on his back in space, possibly reading a book.














Ann

Re: APOD: Stardust in Aries (2017 Dec 09)

by ta152h0 » Sat Dec 09, 2017 5:23 pm

Alot of dirt out there. The big Poobah of the Sky needs to crank up the cosmic shop vac.......Our mancave is getting messy..

Re: APOD: Stardust in Aries (2017 Dec 09)

by Chris Peterson » Sat Dec 09, 2017 3:01 pm

distefanom wrote:"Collapsing due to self-gravity..."

Thinking at all this clutter about the "dark matter", "dark energy", etc... I was wondering if this isn't a way too simple explanation to get reasons of these clumps of matter...
even at these space scales couldn't it be that there are acting also *other* physical phenomena?
Dark energy isn't a factor at this scale. Dark matter could be important, but only through its gravitational effects. The only other forces that might reasonably be considered involve magnetic or electrical fields. These are present in structures like this, but the actual forces they produce are small in comparison to gravity. That said, there may be a small degree of structure in some nebulas that is related to magnetic fields.

It also happens that there are numerical simulations of gas and dust structures, and they demonstrate that gravity alone explains the way they collapse. That is, the models and our observations of natural structures are closely matching, which is strong evidence that our understanding of the mechanisms involved is accurate.

Re: APOD: Stardust in Aries (2017 Dec 09)

by BDanielMayfield » Sat Dec 09, 2017 2:47 pm

heehaw wrote:
distefanom wrote:"Collapsing due to self-gravity..."

Thinking at all this clutter about the "dark matter", "dark energy", etc... I was wondering if this isn't a way too simple explanation to get reasons of these clumps of matter...
even at these space scales couldn't it be that there are acting also *other* physical phenomena?
Of course there could be. But there is no current need for it. Both dark matter and dark energy were introduced as notions (or stuffs) when clear need for them became apparent from the ever-improving observations.
True, but lately it seems that ever-improving observations may be reversing the trend. It could be that the need for these so called "dark" notions can be explained away with better theory.

Re: APOD: Stardust in Aries (2017 Dec 09)

by heehaw » Sat Dec 09, 2017 9:53 am

distefanom wrote:"Collapsing due to self-gravity..."

Thinking at all this clutter about the "dark matter", "dark energy", etc... I was wondering if this isn't a way too simple explanation to get reasons of these clumps of matter...
even at these space scales couldn't it be that there are acting also *other* physical phenomena?
Of course there could be. But there is no current need for it. Both dark matter and dark energy were introduced as notions (or stuffs) when clear need for them became apparent from the ever-improving observations.

Re: APOD: Stardust in Aries (2017 Dec 09)

by Boomer12k » Sat Dec 09, 2017 9:24 am

Awesome piece of work....

:---[===] *

Re: APOD: Stardust in Aries (2017 Dec 09)

by distefanom » Sat Dec 09, 2017 7:19 am

"Collapsing due to self-gravity..."

Thinking at all this clutter about the "dark matter", "dark energy", etc... I was wondering if this isn't a way too simple explanation to get reasons of these clumps of matter...
even at these space scales couldn't it be that there are acting also *other* physical phenomena?

APOD: Stardust in Aries (2017 Dec 09)

by APOD Robot » Sat Dec 09, 2017 5:06 am

Image Stardust in Aries

Explanation: This composition in stardust covers over 8 degrees on the northern sky. The mosaicked field of view is west of the familiar Pleiades star cluster, toward the zodiacal constellation Aries and the plane of our Milky Way Galaxy. At right in the deep skyscape is bluish Epsilon Arietis, a star visible to the naked-eye and about 330 light-years away. Reflecting starlight in the region, dusty nebulae LBN762, LBN753, and LBN743 sprawl left to right across the field, but are likely some 1,000 light-years away. At that estimated distance, the cosmic canvas is over 140 light-years across. Near the edge of a large molecular cloud, their dark interiors can hide newly formed stars and young stellar objects or protostars from prying optical telescopes. Collapsing due to self-gravity, the protostars form around dense cores embedded in the molecular cloud.

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