Starship Asterisk*

by **VictorBorun** » Sat Dec 03, 2022 4:42 pm

HST over JWST
...

: Click to view full size image 1 or image 2

by **VictorBorun** » Thu Dec 01, 2022 8:14 pm

Chris Peterson wrote: ↑Fri Oct 21, 2022 3:01 pm
michaelstreeter101 wrote: ↑Fri Oct 21, 2022 8:00 am Hi,

Do you think the smaller diffraction spikes in JWST images could have been completely eliminated if they had simply coated the 3 struts supporting the secondary mirror with a metamaterial that cloaked infrared light?
No. That technology doesn't exist. Small steps have been made in using metamaterials to alter optical properties like diffraction, but only at a microscopic or nearly microscopic scale. Furthermore, it's unlikely that this would even be physically possible over the 50-fold wavelength range that the JWST operates across.

Looking at the latest JWST team's reprocessing, you hardly mind the diffraction spikes:

I think I can see now that

1) the bridge between two pillars: the one in the middle and the one at right, — is in fact an overlay from another plane
2) the three pillars as a whole look like three rings' segments, where the rings are concentric and maybe almost in the same spherical shell (like the ribs in a breastchest) while the segments that survive are almost parallel to the stellar wind from the blue giant stars beyond the frame's top right corner

by **Chris Peterson** » Fri Oct 21, 2022 3:01 pm

michaelstreeter101 wrote: ↑Fri Oct 21, 2022 8:00 am Hi,

Do you think the smaller diffraction spikes in JWST images could have been completely eliminated if they had simply coated the 3 struts supporting the secondary mirror with a metamaterial that cloaked infrared light?

No. That technology doesn't exist. Small steps have been made in using metamaterials to alter optical properties like diffraction, but only at a microscopic or nearly microscopic scale. Furthermore, it's unlikely that this would even be physically possible over the 50-fold wavelength range that the JWST operates across.

by **johnnydeep** » Fri Oct 21, 2022 2:30 pm

michaelstreeter101 wrote: ↑Fri Oct 21, 2022 8:00 am Hi,

Do you think the smaller diffraction spikes in JWST images could have been completely eliminated if they had simply coated the 3 struts supporting the secondary mirror with a metamaterial that cloaked infrared light?

Thanks,

Michael

Intriguing idea. Sadly, I know nothing about either the science or feasibility of doing that, but if it was possible I'm sure it would be used, and so far it hasn't been.

by **michaelstreeter101** » Fri Oct 21, 2022 8:00 am

Hi,

Do you think the smaller diffraction spikes in JWST images could have been completely eliminated if they had simply coated the 3 struts supporting the secondary mirror with a metamaterial that cloaked infrared light?

Thanks,

Michael

by **Chris Peterson** » Thu Oct 20, 2022 9:33 pm

VictorBorun wrote: ↑Thu Oct 20, 2022 9:18 pm
Chris Peterson wrote: ↑Thu Oct 20, 2022 1:06 pm
VictorBorun wrote: ↑Thu Oct 20, 2022 12:53 pm

I guess electric charging matters at a finish line in a thick disk around the centre of collapse.
But the spooky dusty arm of a galaxy must be collision free to exist for millions of years, must it not?
Why?
Suppose there was a dust cloud pushed away from a galaxy by light and stellar wind. Fractions of smaller and larger dust particles were moving at different velocities, and the friction were making them electrically charged, like regions in a storm cloud.
A region of the same sign electric charge will blow up by the force of repulsion.
Two regions of opposite signs will mix by the force of attraction.
In the end electrically charged regions outside the galaxy will not stay

I don't think that happens. Dust clouds are not stable. They dissipate as they are pushed away from their sources, and in some cases they condense again due to gravity in gas clouds. Pillars like these are at about the end state of condensation, except where stars are forming, and are starting to be pushed apart again by stellar winds and radiation. Collisional processes are certainly occurring all the time.

by **VictorBorun** » Thu Oct 20, 2022 9:18 pm

Chris Peterson wrote: ↑Thu Oct 20, 2022 1:06 pm
VictorBorun wrote: ↑Thu Oct 20, 2022 12:53 pm
Chris Peterson wrote: ↑Thu Oct 20, 2022 12:27 pm

Dust easily acquires an electric charge, resulting in attractive forces between particles, meaning it is not "collision-free". Nor is it safe to assume that dark matter is collision free, as the general view is that it can interact with itself.
I guess electric charging matters at a finish line in a thick disk around the centre of collapse.
But the spooky dusty arm of a galaxy must be collision free to exist for millions of years, must it not?
Why?

Suppose there was a dust cloud pushed away from a galaxy by light and stellar wind. Fractions of smaller and larger dust particles were moving at different velocities, and the friction were making them electrically charged, like regions in a storm cloud.
A region of the same sign electric charge will blow up by the force of repulsion.
Two regions of opposite signs will mix by the force of attraction.
In the end electrically charged regions outside the galaxy will not stay

by **VictorBorun** » Thu Oct 20, 2022 9:08 pm

orin stepanek wrote: ↑Thu Oct 20, 2022 1:18 pm stsci-pillarsofcreation1280c.jpg
Never noticed it before this but it looks
like a creature praying!

M16_final_1024.jpg

Kinda looks as though the pillars are inside a human head!!!

Krishna?

By the way, It should be nicknamed The Praying Mantis

by **Ann** » Thu Oct 20, 2022 6:51 pm

Locutus76 wrote: ↑Thu Oct 20, 2022 6:06 pm
Ann wrote: ↑Thu Oct 20, 2022 4:40 am This comparison between the Hubble and the Webb portraits of the Pillars is fantastic!

Does anyone know why many of the orange/yellow stars in the Webb image don’t show up in the Hubble image? Seems that only the blue ones are visible in the Hubble image

That is because the stars picked up by Webb but not by Hubble are very cool and predominantly infrared. Hubble primarily detects optical light emitted by warm or hot stars, but Webb is an infrared-sensitive telescope sensitive to cool or very cool stars.

Ann

by **Locutus76** » Thu Oct 20, 2022 6:06 pm

Ann wrote: ↑Thu Oct 20, 2022 4:40 am This comparison between the Hubble and the Webb portraits of the Pillars is fantastic!

Does anyone know why many of the orange/yellow stars in the Webb image don’t show up in the Hubble image? Seems that only the blue ones are visible in the Hubble image

by **orin stepanek** » Thu Oct 20, 2022 1:18 pm

Never noticed it before this but it looks
like a creature praying!

Kinda looks as though the pillars are inside a human head!!!

by **Chris Peterson** » Thu Oct 20, 2022 1:06 pm

VictorBorun wrote: ↑Thu Oct 20, 2022 12:53 pm
Chris Peterson wrote: ↑Thu Oct 20, 2022 12:27 pm
VictorBorun wrote: ↑Thu Oct 20, 2022 12:16 pm Dust by itself is collision-free, like dark matter.
Dust easily acquires an electric charge, resulting in attractive forces between particles, meaning it is not "collision-free". Nor is it safe to assume that dark matter is collision free, as the general view is that it can interact with itself.
I guess electric charging matters at a finish line in a thick disk around the centre of collapse.
But the spooky dusty arm of a galaxy must be collision free to exist for millions of years, must it not?

Why?

by **VictorBorun** » Thu Oct 20, 2022 12:53 pm

Chris Peterson wrote: ↑Thu Oct 20, 2022 12:27 pm
VictorBorun wrote: ↑Thu Oct 20, 2022 12:16 pm Dust by itself is collision-free, like dark matter.
Dust easily acquires an electric charge, resulting in attractive forces between particles, meaning it is not "collision-free". Nor is it safe to assume that dark matter is collision free, as the general view is that it can interact with itself.

I guess electric charging matters at a finish line in a thick disk around the centre of collapse.
But the spooky dusty arm of a galaxy must be collision free to exist for millions of years, must it not?

by **Chris Peterson** » Thu Oct 20, 2022 12:27 pm

VictorBorun wrote: ↑Thu Oct 20, 2022 12:16 pm Dust by itself is collision-free, like dark matter.

Dust easily acquires an electric charge, resulting in attractive forces between particles, meaning it is not "collision-free". Nor is it safe to assume that dark matter is collision free, as the general view is that it can interact with itself.

by **VictorBorun** » Thu Oct 20, 2022 12:16 pm

Ann wrote: ↑Thu Oct 20, 2022 9:31 am
AM 1316dash241 NASA ESA Hubble Heritage.png
Overlapping galaxies AM 1316-241 by NASA/ESA/Hubble Heritage.

You can see in the image of overlapping galaxies AM 1316-124 that the foreground spiral galaxy has a long stretch of dusty arm that forms very few stars.

Ann

And I just don't get it. Why is the dust arm there?
Dust is a solid, effective radiator of the heat.
A gas and dust cloud must radiate the heat from the dust particles and they must cool down the gas.
Gas cloud of low velocity molecules must easily collapse since it has a way to radiate the heat of collapsing, through dust.
There is a problem for a collapsing cloud to shed the spin, but it's solved by spitting lighter fractions at greater velocities.

Can it be that the dust clouds are stable if they have too little gas?
Dust by itself is collision-free, like dark matter.
But dust and gas is viscous only if the gas is dense.

by **jisles** » Thu Oct 20, 2022 12:14 pm

Serpens Cauda is not a constellation and it's not split. Serpens is the constellation, but indeed that has two parts: Serpens Caput and Serpens Cauda.

John

by **Ann** » Thu Oct 20, 2022 9:31 am

VictorBorun wrote: ↑Thu Oct 20, 2022 7:10 am 5) if this dust pillars-on-larger pillars fractal is tails of dense gas-and-dust clumps, why the nebula had such clumps in the first place?
I mean, the moment a dusty nebula is cooled by its dust's thermal radiation every clump is going to collapse to a sun, a red dwarf, a brown dwarf, a rogue planet, an interstellar asteroid, a dusty flake, anything. It would not wait for some blue giants to slowly form in a low-metallicity low-dust pocket and start shaping the pillars

Dust is clumpy, because it is formed by discrete sources.

: Wolf-Rayet star WR 124, a dust factory. Image: ESA/Hubble.

: Our Galaxy in Stars, Gas, and Dust Credit & Copyright: John P. Gleason, Celestial Images

Once the dust has formed, its distribution is affected by various factors and processes in the galaxy, such as the galaxy's rotation, magnetic field lines, stellar winds from hot stars, supernovas etc.

Just because dust is present doesn't mean that stars will necessarily form in it. Star formation is even more clumpy than the distribution of dust.

Overlapping galaxies AM 1316-241 by NASA/ESA/Hubble Heritage.

You can see in the image of overlapping galaxies AM 1316-124 that the foreground spiral galaxy has a long stretch of dusty arm that forms very few stars.

Ann

by **VictorBorun** » Thu Oct 20, 2022 7:10 am

5) if this dust pillars-on-larger pillars fractal is tails of dense gas-and-dust clumps, why the nebula had such clumps in the first place?
I mean, the moment a dusty nebula is cooled by its dust's thermal radiation every clump is going to collapse to a sun, a red dwarf, a brown dwarf, a rogue planet, an interstellar asteroid, a dusty flake, anything. It would not wait for some blue giants to slowly form in a low-metallicity low-dust pocket and start shaping the pillars

by **Ann** » Thu Oct 20, 2022 6:43 am

VictorBorun wrote: ↑Thu Oct 20, 2022 5:52 am are add-on IR stars all red dwarves?
which stars are background and which are foreground and which are aborigens?
where are all distant galaxies?
where are all Herbig-Haro jets?

1) Yes, it is likely that the added IR stars are red dwarf stars, for the simple reason that star formation in dusty pillars typically creates low-mass stars. There is rarely enough starforming material in pillars to create massive stars, at least if you ask me.

Anyway, stars that are visible in IR images and invisible in optical ones are likely to be low in mass, and therefore, they are red dwarfs. Admittedly stars that are extremely obscured by dust may well be massive, but I think they will look "special" in IR. They will stand out very much from their environment, I think, and/or they may be surrounded by a cluster of smaller stars. I don't think we are seeing anything like that in the Webb portrait of the Pillars of Creation.

Two massive stars are forming in the Serpent Nebula.

2) We can't say which stars are foreground objects and which stars belong to the Eagle Nebula without measuring their parallaxes. That is a job for Gaia. However, the O- and B-type stars that are found close to the Pillars are almost certainly part of the Eagle Nebula, because there will be no emission nebulas unless there are hot stars there to ionize them.

3) Even Webb can't see any background galaxies in the Eagle Nebula. That is because the Eagle Nebula is located in the dense dust lane of the Milky Way, and all background galaxies are hidden behind all this dust. The area close to the Milky Way dust lane used to be called "the zone of avoidance", because no galaxies were found here.

: Location of M16 (the Eagle Nebula) and other Messier objects in a part of the Milky Way dust lane. Image: Wikisky.

4) Herbig-Haro objects are not my forte. At all! But I think we are seeing jets in the Webb image, and one jet is visible in the Hubble image, too.

Ann

by **VictorBorun** » Thu Oct 20, 2022 5:52 am

are add-on IR stars all red dwarves?
which stars are background and which are foreground and which are aborigens?
where are all distant galaxies?
where are all Herbig-Haro jets?

by **VictorBorun** » Thu Oct 20, 2022 5:42 am

...

: Click to view full size image 1 or image 2

: Click to view full size image 1 or image 2

processed out stars version is by Mehmet Ergün

by **Ann** » Thu Oct 20, 2022 4:40 am

This comparison between the Hubble and the Webb portraits of the Pillars is fantastic!

It's a bother to write captions when the picture is so large that you can't use img3, because it is so hard to fit the text below the picture when you use attachments, but this is the caption from NASA of the image I posted:

NASA wrote:

NASA's Hubble Space Telescope made the Pillars of Creation famous with its first image in 1995, but revisited the scene in 2014 to reveal a sharper, wider view in visible light, shown above at left. A new, near-infrared-light view from NASA’s James Webb Space Telescope, at right, helps us peer through more of the dust in this star-forming region. The thick, dusty brown pillars are no longer as opaque and many more red stars that are still forming come into view.
Credits: NASA, ESA, CSA, STScI; Joseph DePasquale (STScI), Anton M. Koekemoer (STScI), Alyssa Pagan (STScI).

Do spend some time comparing the Hubble and the Webb images. It is fascinating indeed!

Ann

Edit: According to the APOD caption, the distance to the Eagle Nebula (and thus to the Pillars of Creation) is some 6,500 light-years. According to Simbad Astronomical Database, the Gaia parallax for the bright blue star at upper center in the Webb image, or at upper left in the Webb panel of the Hubble/Webb comparison image that I posted here, is 0.5316 milliarcseconds, with an uncertainty of 0.0256 milliarcseconds. A parallax of 0.5316 milliarcseconds corresponds to a distance of 1881 parsecs, or some 6,100 light-years.

by **bystander** » Thu Oct 20, 2022 4:24 am

Webb Takes Star-Filled Portrait of Pillars of Creation
NASA | ESA | CSA | STScI | 19 Oct 2022

by **APOD Robot** » Thu Oct 20, 2022 4:06 am

Pillars of Creation

Explanation: A now famous picture from the Hubble Space Telescope featured these star forming columns of cold gas and dust light-years long inside M16, the Eagle Nebula, dubbed the Pillars of Creation. This James Webb Space Telescope NIRCam image expands Hubble's exploration of that region in greater detail and depth inside the iconic stellar nursery. Particularly stunning in Webb's near infrared view is the telltale reddish emission from knots of material undergoing gravitational collapse to form stars within the natal clouds. The Eagle Nebula is some 6,500 light-years distant. The larger bright emission nebula is itself an easy target for binoculars or small telescopes. M16 lies along the plane of our Milky Way galaxy in a nebula rich part of the sky, toward the split constellation Serpens Cauda (the tail of the snake).

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