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James Webb Telescope

Ziggurat said:
Oxygen can disolve in water, and anything on the ocean floor can still react with that oxygen. Being covered in water doesn't prevent oxidation.
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Yeah, I thought about that and also that dissolved material in the ocean might oxidize. Even if you add the requirement that the sea floor be oxidized it doesn't seem to be an obstacle to the conclusion that there could be planets with enough water to overwhelm the available surface oxygen sinks.

I didn't think about this too hard but there seem to be a couple of factors that are overwhelming: gaseous hydrogen is easily stripped from the surface of a planet; oxygen is the third most common element; the vast majority of oxygen sinks are in the core of the planet.

Not sure if I'm right about that last assumption. I think it's the current consensus that the core and outer core are oxygen deficient.

Isn't it the case now on Earth that the surface (land and sea floor) are nearly completely oxidized?

Biomass seems to be about two or three orders of magnitude short of being a sufficient sink.

Of course, there is also the simple point that oxygen on a planet around a star that isn't particular bright in UV wouldn't be explained by this mechanism.
 
Thought this was interesting too:



So the short version as I understand it is that galaxies in the early universe look more orderly and disc-like in the JWST images than they appeared in earlier Hubble images. The reason is fairly straightforward and understandable once you think it through. Hubble sees light in a shorter wavelength range than JWST. At high redshifts that means that it was originally UV or shorter wavelengths which have been redshifted into visible wavelengths. But those high-energy wavelengths tend to be clustered in star-forming regions of galaxies, so they end up looking lumpier. Whereas the light JWST sees is visible light that has been shifted into the infrared. So it looks more like what we would see in visible wavelengths if we were closer.
 
RecoveringYuppy said:
That's what my next sentence was addressing. If there is nothing to absorb it then it accumulates.
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What I mean is that I don't see how dissociation of H2O would create oxygen (the diatomic molecule) in the first place. It creates a couple of radicals, not free atoms of O. So there's more work to be done. If the rate of recombination of those radicals is greater than the rate for some other forward reaction, then there will be no significant production of O2.

Water self-dissociates all the time, it just normally recombines back to water pretty quickly. I don't know a mechanism for UV dissociation of water to cause O2 production.
 
BowlOfRed said:
What I mean is that I don't see how dissociation of H2O would create oxygen (the diatomic molecule) in the first place. It creates a couple of radicals, not free atoms of O. So there's more work to be done. If the rate of recombination of those radicals is greater than the rate for some other forward reaction, then there will be no significant production of O2.

Water self-dissociates all the time, it just normally recombines back to water pretty quickly. I don't know a mechanism for UV dissociation of water to cause O2 production.
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I was assuming Earth gravity or less. Hydrogen can escape Earth's gravity at temperatures on Earth.
 
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NASA releases pictures of exoplanet ‘six to 12 times the mass of Jupiter’ in unprecedented detail

It might look like a couple of colourful smudges but it could be the next step in finding habitable planets outside our own.

NASA has released the first picture of HIP 65426 b, an exoplanet that's six to 12 times the mass of Jupiter.

It marks the first time that astronomers have used NASA’s James Webb Space Telescope to take a direct image of a planet outside our solar system.

The image — as seen through four different light filters — shows how Webb’s powerful infrared gaze can easily capture worlds beyond our solar system, pointing the way to future observations that will reveal more information than ever before about exoplanets.
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I've seen this photo, but it confuses me. Is the planet only visible in the zoomed-in part on the far right? Is the whole blob the planet? Is that a star or a planet in the other three images, and finally what is the five-pointed star symbol?
 
Puppycow said:
I've seen this photo, but it confuses me. Is the planet only visible in the zoomed-in part on the far right? Is the whole blob the planet? Is that a star or a planet in the other three images, and finally what is the five-pointed star symbol?
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Those are all images of the planet and I'm fairly sure the star icon is used to align the images if you intend to overlay them.

It's the same planet in all four pictures in four different parts of the spectrum.

ETA: Why do you think the far right picture is "zoomed in"? I don't think it is.
 
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RecoveringYuppy said:
Those are all images of the planet and I'm fairly sure the star icon is used to align the images if you intend to overlay them.

It's the same planet in all four pictures in four different parts of the spectrum.

ETA: Why do you think the far right picture is "zoomed in"? I don't think it is.
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I think all four of them are zoomed in, but only the one on the far right has a caption that says "planet". It points to the upper left edge of the blob. That is the source of my confusion.
 
RecoveringYuppy said:
Those are all images of the planet and I'm fairly sure the star icon is used to align the images if you intend to overlay them.

It's the same planet in all four pictures in four different parts of the spectrum.

ETA: Why do you think the far right picture is "zoomed in"? I don't think it is.
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I was under the impression that the star icon indicated the location of the actual star. I am sure I might be wrong about that.
 
Puppycow said:
Enlarged.
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But I'm still not sure what that would mean in this context.

Susheel said:
I was under the impression that the star icon indicated the location of the actual star. I am sure I might be wrong about that.
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I'll go with Nature on that then. Other sources seemed to say it was the shadow of the occulter which I think is wrong. But being where the shadow of the occulter was makes sense.
 
I was excited to see in the that the planet's a year-days light-years away. Then later in the article it's 385 light years away. So either space is expanding several times faster than c between us and the planet, or it's a typo.
 
Lennart Hyland said:
Yes, atleast thats how Nature.com explains it:
The star symbol marks the exoplanet HIP 65426 b’s star, which Webb has blocked from the image
https://www.nature.com/articles/d41586-022-02807-4
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So, if we assume the pixelation shown in that image is the native pixelation then that is about 5K pixels a subset of the total 4M pixels for that instrument. So that possibly explains the "zoomed in" description. And then that would imply the occulter blocks out about 25 pixels cleanly which I find impressive.

So does anyone know if this planet is nearly aligned in front of or behind it's parent star? If I've done my arithmetic correctly it must be close or it would be out of the frame.
 
sphenisc said:
I was excited to see in the that the planet's a year-days light-years away. Then later in the article it's 385 light years away. So either space is expanding several times faster than c between us and the planet, or it's a typo.
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1 year/1 day = 365, which is close to 385. I suspect it's not a typo, but just a really weird way of presenting something close to the scale of 385. I think it's a bad choice, but that's probably where it comes from.
 
Ziggurat said:
1 year/1 day = 365, which is close to 385. I suspect it's not a typo, but just a really weird way of presenting something close to the scale of 385. I think it's a bad choice, but that's probably where it comes from.
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For me it's bloody awful writing because it's taken your post and some brainwork to work out what "a year-days light-years away" actually means.

How can that possibly be viewed as making '385 light years' seem simpler??? Expecially when a 'light day' is already a unit of distance (if not often used).
 
Was that year-days thing actually in an article or was sphensic poking fun at another thread on this forum?
 
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