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James Webb Space Telescope Finds Most Distant Known Galaxy

blogs.nasa.gov

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Re: James Webb Space Telescope Finds Most Distant Known Galaxy

#41

Post by codezero »

dredmorbius wrote: post #38
thallium205 wrote: post #35

Earlier quoted context omitted.

The JWT cost more both in dollars and time than the Manhattan Project.

Not if you're looking at inflation-adjusted dollars, though the values are closer than I'd have thought. 1945 cost of the Manhattan Project, $1.89 billion,[1] or $32.9 billion 2024 per https://www.usinflationcalculator.com/ >. 2016 cost of the JWST: ~$10 billion,[2] or $13.1 billion 2024 adjusted for inflation. That's a smaller multiple for the Manhattan Project than I'd have expected, but it's still comfortably more…

arguably we wouldn't have JWST without Hubble, so cost adjusted they're about the same, then again, there is probably some "prior art expensive project" associated with Manhattan, but I didn't check :)

Re: James Webb Space Telescope Finds Most Distant Known Galaxy

#42

Post by prawn »

kloch wrote: post #16
phaedrus wrote: post #5

I wonder if a galaxy like this could be so bright as to support life on rogue planets i.e. those not orbiting a star? (If there would be any elements to create a rocky planet from. However the article states they were surprised to detect signs of dust and oxygen already in such an early galaxy.)

Only maybe in the dense core of a galaxy because incident radiation falls off with the square of distance. The nearest star to us after the Sun is ~4ly away, or ~250k AU. The Sun would have to be ~63 billion times brighter to give the same incident radiation at 250k AU, and that is just a typical distance between stars in our neighborhood . The Sun is also brighter than the average star, especially the older stars th…

Carrying on from that first sentence:

"in the center of the galaxy, stars are only 0.4–0.04 light-years apart"

The most luminous stars going by Wikipedia are about 5 million times brighter than the Sun. Not sure if those are anywhere near galactic centres though.

Re: James Webb Space Telescope Finds Most Distant Known Galaxy

#45

Post by codezero »

tiahura wrote: post #43

1. Why doesn't the press release state the actual distance? ChatGPT says about 30 billion light years. 2. How can we observe objects 30 billion light years away, but can't rule out another planet past pluto?

this is a slice of a tiny, tiny, tiny piece of space in a particular spectrum.

Also, relative motion is a thing. It's easier to bin a lot of images from distant, stationary objects than to do so for "nearby" moving objects.

If you google "why can't we image the Moon with hubble"

You'll find a lot of better answers like https://www.reddit.com/r/askscience/comments/jd83ue/why_is_i...

Other funky reasons: long exposure images through small slices of the sky can have less noise than "larger" chunks nearby, that are moving. Nearby objects need to deal with things like the zodiacal light, gegenshein, astroids, the glare of the Sun and reflections off of planets and a number of other things, as well as the glare of stars, which there are many more of in larger fields of view than 6 arc minutes.

A bad analogy:

this is imaging a gnat through a empty space in a square of a screen door. What you want to see is a bear through Gauze.

Re: James Webb Space Telescope Finds Most Distant Known Galaxy

#46

Post by [deleted] »

codezero wrote: post #45
tiahura wrote: post #43

1. Why doesn't the press release state the actual distance? ChatGPT says about 30 billion light years. 2. How can we observe objects 30 billion light years away, but can't rule out another planet past pluto?

this is a slice of a tiny, tiny, tiny piece of space in a particular spectrum. Also, relative motion is a thing. It's easier to bin a lot of images from distant, stationary objects than to do so for "nearby" moving objects. If you google "why can't we image the Moon with hubble" You'll find a lot of better answers like https://www.reddit.com/r/askscience/comments/jd83ue/why_is_i... Other funky reasons: long exposure…

[deleted]

Re: James Webb Space Telescope Finds Most Distant Known Galaxy

#47

Post by astro-throw »

codezero wrote: post #44

I could be armchair astronomying wrong here - but something that blows my mind: this image represents 6.2 arcminutes across in the field of view, that's 10x smaller than the size of Andromeda in the night sky. Imagine what's behind Andromeda!?

… imagine what’s behind our galaxy!

Re: James Webb Space Telescope Finds Most Distant Known Galaxy

#48

Post by codezero »

astro-throw wrote: post #47
codezero wrote: post #44

I could be armchair astronomying wrong here - but something that blows my mind: this image represents 6.2 arcminutes across in the field of view, that's 10x smaller than the size of Andromeda in the night sky. Imagine what's behind Andromeda!?

… imagine what’s behind our galaxy!

everything and nothing :)

Re: James Webb Space Telescope Finds Most Distant Known Galaxy

#49

Post by astro-throw »

dredmorbius wrote: post #37
throwawaymaths wrote: post #22

Earlier quoted context omitted.

Pop III stars (if they existed) are really a mystery, we can't easily extrapolate. These stars would be purely hydrogen and helium so it would take them a surprisingly long time to get to CNO cycle, for example.

Why would it take a Pop III star longer than an equivalent-mass Pop I or II star to reach the end of its H / He fusion cycle?

Because of the lack of C, N, and O, which are catalysts in the CNO cycle. They aren't produced by it.

Re: James Webb Space Telescope Finds Most Distant Known Galaxy

#50

Post by radarsat1 »

astroH wrote: post #14
boringg wrote: post #12

Anyone know the algorithmic approach to finding this? I assume they ran an ML over the dataset with a search function to figure it out.

It's a lot less sophisticated than that. They take images in multiple filters. In the context of JWST of order 10 filters (sometimes more sometimes less). Source extraction is then performed on the images by essentially identifying bright spots and dropping an aperture (separating ones that are nearby and blended if possible). The standard tool for this is called source extractor. They then have catalogs of tens of t…

> less sophisticated

lol.

Thanks for this breakdown, it was super interesting to read about what signal processing techniques are used for this kind of thing!

How does the actual "searching" take place, do they just run this kind of procedure at every bright spot in the image and rank candidate sections?

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