51–59 of 59 posts
Earlier quoted context omitted.
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 :)
Hubble itself strongly leveraged Key Hole, as a further extension:
https://en.wikipedia.org/wiki/KH-11_KENNEN>
As for the Manhattan Project, it was sufficiently close to the first direct theoretical and applied theory and proofs of sustainable nuclear chain reactions (roughly a decade or less following each), and a lack of understanding of the corresponding risks (which greatly increase costs) that there simply wasn't time to have spent all that much money.
By contrast, Hubble and JWST are both late-stage, highly-evolved technologies, pushing the engineering envelope in many dimensions simultaneously, all of which tends to increase costs.
See for example the ELT (extremely large telescope), an Earth-based instrument currently under construction in Chile as part of ESO (European Southern Observatory). Tom Scott's 'splainer video on the project explains how costs risk exponentially with increased size for numerous reasons.
https://en.wikipedia.org/wiki/Extremely_Large_Telescope>
https://yewtu.be/watch?v=QqRREz0iBes>
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…
Also thanks for the detailed response - their approach sounds like a smart solution minimizing unnecessary compute cost / algorithm scanning.
Earlier quoted context omitted.
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.
Or am I missing something?
Earlier quoted context omitted.
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…
If I understand this correctly its like a mask between filters and the differential makes that differential much more noticeable? Wouldn't one of the challenges be that the pictures have to be almost the exact same time with those filters so that they line up perfectly to provide the differential given the high resolution? Also thanks for the detailed response - their approach sounds like a smart solution minimizing…
Earlier quoted context omitted.
Because of the lack of C, N, and O, which are catalysts in the CNO cycle. They aren't produced by it.
NB: based on some quick searches, it seems that low-metalicity Pop III stars would rely on the pp (proton-proton) fusion chain. That's going to slow reaction somewhat, and extend lifetime. But for high-mass stars with only a few millions of years expected lifetime in a Pop I/II class, that's ... still a relatively modest difference compared to the several hundred million year lifespan of the early Universe. Or am I m…
Earlier quoted context omitted.
NB: based on some quick searches, it seems that low-metalicity Pop III stars would rely on the pp (proton-proton) fusion chain. That's going to slow reaction somewhat, and extend lifetime. But for high-mass stars with only a few millions of years expected lifetime in a Pop I/II class, that's ... still a relatively modest difference compared to the several hundred million year lifespan of the early Universe. Or am I m…
Another interesting quirk of Pop III stars is that their initial mass function is expected to form much more massive stars than Pop II or Pop I. So even if Pop III stars are longer lived at the same mass as Pop II or Pop I, there will be a lot more supernovae per time, leading to fast enrichment and then Pop II.
Another is that p-p fusion is fairly common. Look up when the Big Room's bright and you'll see a ... stellar example yourself ;-)
(p-p fusion dominates in stars < ~1.3 M, where M is a solar mass. CNO fusion is typical of more massive stars.)