APOD: Star Cluster IC 348 from Webb (2024 Jan 15)

[APOD Robot]

Star Cluster IC 348 from Webb

Explanation: Sometimes, it's the stars that are the hardest to see that are the most interesting. IC 348 is a young star cluster that illuminates surrounding filamentary dust. The stringy and winding dust appears pink in this recently released infrared image from the Webb Space Telescope. In visible light, this dust reflects mostly blue light, giving the surrounding material the familiar blue hue of a reflection nebula. Besides bright stars, several cool objects have been located in IC 348, visible because they glow brighter in infrared light. These objects are hypothesized to be low mass brown dwarfs. Evidence for this includes the detection of an unidentified atmospheric chemical, likely a hydrocarbon, seen previously in the atmosphere of Saturn. These objects appear to have masses slightly greater than known planets, only a few times greater than Jupiter. Together, these indicate that this young star cluster contains something noteworthy -- young planet-mass brown dwarfs that float free, not orbiting any other star.

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[Ann]

This is JWST's portrait of star cluster IC 348:

Star Cluster IC 348 from Webb. Image Credit: NASA, ESA, CSA, STScI, and K. Luhman (Penn State U.) and C. Alves de Oliveira (ESA)

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This is Mark Hanson's superb visible-light portrait of IC 348:

IC 348. Credit: Mark Hanson

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Here is a wonderful labeled version of Mark Hanson's portrait. The labeling is provided by Sakib Rasool:

I would love to see an "overlay" that shows us how Webb's image fits together with optical images.

Ann

[AVAO]

...
I would love to see an "overlay" that shows us how Webb's image fits together with optical images.

Ann

Right in the center Jac

Click to view full size image

[JohnD]

It's not April 1st, but how else to account for this sentence inserted into the blurb for this APoD?
"Evidence for this includes the detection of an unidentified atmospheric chemical, likely a hydrocarbon, seen previously in the atmosphere of Saturn."

If you wish for confirmation of this allegation, click on the second link, on "unidentified"!
JOhn

[johnnydeep]

...
I would love to see an "overlay" that shows us how Webb's image fits together with optical images.

Ann

Right in the center Jac

Click to view full size image

Nice! How do you manage to always do this so well, even when the sizes of the field of view differ so greatly?

[ EDIT: ok, this was easier than I first though since I didn't notice that Ann pointed to the location of IC 348 in her annotated image! ]

Also, what are the two other insets showing?

[Chris Peterson]

...
I would love to see an "overlay" that shows us how Webb's image fits together with optical images.

Ann

Right in the center Jac

Click to view full size image

Nice! How do you manage to always do this so well, even when the sizes of the field of view differ so greatly?

[ EDIT: ok, this was easier than I first though since I didn't notice that Ann pointed to the location of IC 348 in her annotated image! ]

Also, what are the two other insets showing?

Also, you can trivially solve the optical images to get the scale and coordinates (astrometry.com), and the JWST images are released with the image coordinates provided. That info does most of the work for you.

[Fred the Cat]

Somehow the description failed to mention the star-forming nature of these filaments. From the Pleiades to galaxies to our Magellanic Clouds, filaments seem to be quite important.

JWST investigation seems to be hot on the trail. " Musca" not decided to go into that.

[johnnydeep]

Right in the center Jac

Click to view full size image

Nice! How do you manage to always do this so well, even when the sizes of the field of view differ so greatly?

[ EDIT: ok, this was easier than I first though since I didn't notice that Ann pointed to the location of IC 348 in her annotated image! ]

Also, what are the two other insets showing?

Also, you can trivially solve the optical images to get the scale and coordinates (astrometry.com), and the JWST images are released with the image coordinates provided. That info does most of the work for you.

Ah. "Trivial" for the well-informed! I'll have to try that astrometry.com site sometime.

[johnnydeep]

It's not April 1st, but how else to account for this sentence inserted into the blurb for this APoD?
"Evidence for this includes the detection of an unidentified atmospheric chemical, likely a hydrocarbon, seen previously in the atmosphere of Saturn."

If you wish for confirmation of this allegation, click on the second link, on "unidentified"!
JOhn

What's your beef? There are often links to "cute" cat and dog images. But the sentence you call out sure doesn't seem too convincing: evidence from something unidentified doesn't sound very definitive! But the linked paper goes into more detail with more rationale.

[johnnydeep]

Alright, after much googling I have been unable to determine how long brown dwarves can maintain fusion of deuterium or lithium. Billions of years? Trillions?

Ok, apparently they can't fuse for very long at all, judging by this:

Brown dwarfs are an odd set of objects that are neither planets nor stars. Rather than forming like planetary seeds in the disks around protostars, brown dwarfs begin on their own like stellar seeds. However, they never pull in enough material to start nuclear fusion; instead, they slowly contract, cool, and glow in the infrared from the release of gravitational energy, like Jupiter. Eventually, they simply fade away. Some people think of brown dwarfs as failed stars.

Although brown dwarfs never truly become stars, some of them are able to act the part, for a short while. To start fusion, the very lowest-mass stars need about 80 times the mass of Jupiter. However, if a brown dwarf has at least 13 times the mass of Jupiter, it can ignite a limited form of fusion. These brown dwarfs fuse a heavy isotope of hydrogen, called deuterium, into helium, releasing energy like a star. Nuclear fusion ends once the supply of deuterium is used up, and that supply is very limited. Once fusion ends, the brown dwarf goes back to contracting, cooling, and glowing.

[andyg]

Dumb question, probably: could brown dwarfs, or ex-brown dwarfs, which are presumably undetectable, explain the effect of "dark matter"? The dwarfs wouldn't obscure light the way dust does, so how do we know there aren't a lot (or enough) of them?

[johnnydeep]

Dumb question, probably: could brown dwarfs, or ex-brown dwarfs, which are presumably undetectable, explain the effect of "dark matter"? The dwarfs wouldn't obscure light the way dust does, so how do we know there aren't a lot (or enough) of them?

Apparently not:

However, multiple lines of evidence suggest the majority of dark matter is not baryonic [normal matter like protons and neutrons and atoms]:

• Sufficient diffuse, baryonic gas or dust would be visible when backlit by stars.
• The theory of Big Bang nucleosynthesis predicts the observed abundance of the chemical elements. If there are more baryons, then there should also be more helium, lithium and heavier elements synthesized during the Big Bang.[108][109] Agreement with observed abundances requires that baryonic matter makes up between 4–5% of the universe's critical density. In contrast, large-scale structure and other observations indicate that the total matter density is about 30% of the critical density.[92]
• Astronomical searches for gravitational microlensing in the Milky Way found at most only a small fraction of the dark matter may be in dark, compact, conventional objects (MACHOs, etc.); the excluded range of object masses is from half the Earth's mass up to 30 solar masses, which covers nearly all the plausible candidates.[110][111][112][113][114][115]
• Detailed analysis of the small irregularities (anisotropies) in the cosmic microwave background.[116] Observations by WMAP and Planck indicate that around five-sixths of the total matter is in a form that interacts significantly with ordinary matter or photons only through gravitational effects.

[Chris Peterson]

Dumb question, probably: could brown dwarfs, or ex-brown dwarfs, which are presumably undetectable, explain the effect of "dark matter"? The dwarfs wouldn't obscure light the way dust does, so how do we know there aren't a lot (or enough) of them?

I don't think they would be undetectable. They would still be much warmer than the background, and thus visible in long IR wavelengths.

[andyg]

Dumb question, probably: could brown dwarfs, or ex-brown dwarfs, which are presumably undetectable, explain the effect of "dark matter"? The dwarfs wouldn't obscure light the way dust does, so how do we know there aren't a lot (or enough) of them?

Apparently not:

However, multiple lines of evidence suggest the majority of dark matter is not baryonic [normal matter like protons and neutrons and atoms]:

• Sufficient diffuse, baryonic gas or dust would be visible when backlit by stars.
• The theory of Big Bang nucleosynthesis predicts the observed abundance of the chemical elements. If there are more baryons, then there should also be more helium, lithium and heavier elements synthesized during the Big Bang.[108][109] Agreement with observed abundances requires that baryonic matter makes up between 4–5% of the universe's critical density. In contrast, large-scale structure and other observations indicate that the total matter density is about 30% of the critical density.[92]
• Astronomical searches for gravitational microlensing in the Milky Way found at most only a small fraction of the dark matter may be in dark, compact, conventional objects (MACHOs, etc.); the excluded range of object masses is from half the Earth's mass up to 30 solar masses, which covers nearly all the plausible candidates.[110][111][112][113][114][115]
• Detailed analysis of the small irregularities (anisotropies) in the cosmic microwave background.[116] Observations by WMAP and Planck indicate that around five-sixths of the total matter is in a form that interacts significantly with ordinary matter or photons only through gravitational effects.

Thanks! Shoulda checked wikipedia first. (As my Mom used to say, "why don't you go look it up?")