Why did we make just an infrared telescope then? Why don't go into even lower frequencies, surely we would detect something too if we just look?
XorNot•1h ago
Lower frequencies are microwaves and radio waves. We already have the square kilometer array.
jacques_morin•1h ago
The lower the frequency, the larger the wavelength and thus the larger the cupola needed to detect it. That's why radiotelescopes are on earth, they are HUGE.
metalman•59m ago
"just an infrared telescope"
how about you go make yourself conversant with "just" the technical requirements of the main cryogenic pump onboard, leaving out the rest of the thermal management systems for whatever remains of your life, which will have to long in order to fail honorably.
nasretdinov•55m ago
Sorry, I didn't mean it's easy to build, far from it :). I meant "just infrared" in terms of frequency — why not go further? Is there a gap between the current infrared and radio on Earth?
jacquesm•16m ago
Wavelength for electromagnetic waves = c/frequency.
So to 'catch' a certain frequency with a receiver the size of the receiver gets proportionally larger as the frequency drops. Focusing light can be done with relatively small gear. Focusing radio waves, especially when the source is distant requires a massive structure and to keep that structure sufficiently cool and structurally rigid is a major challenge. It is already a challenge for the JWST at the current wavelengths, increasing the wavelength while maintaining the sensitivity would create some fairly massive complications.
In the end this is a matter of funding, and JWST already nearly got axed multiple times due to its expense.
metalman•11m ago
I am poking fun (at your expense) at the notion that because the light is already there, adding other sensors would be feasable. Once you grasp the requirements of building an infrared telescope, you will be going, oh!, damn, wow!
It's actualy not that deep a dive to get a feel for just how special the JWST is from an engineering perspective, and then a look into just how difficult it will be to get visible light from those distances, which may require a interferometric telescope with
multiple huge sub units flying in formation at distances, known to a fraction of the target wave length , but perhaps several hundred thousand km, apart.
doable, but :), just
Sharlin•56m ago
Because near/mid infrared has many uses other than high-z objects, and it’s been something of a relative blind spot to us until now, although before Webb we did have Spitzer.
For far IR/submillimeter observations we had Herschel in space, SOFIA in the stratosphere (flying on a 747), and several large terrestrial telescopes at very high altitudes can also observe at FIR/submm wavelengths. But sure, there are likely many astronomers who would love nothing more than a new spaceborne FIR telescope, given that it’s been more than a decade since Herschel’s end of mission, and SOFIA was also retired in 2022.
For microwave we’ve had several space telescopes (COBE, then WMAP, then Planck), mainly designed to map the cosmic microwave background. That’s the farthest and reddest that you can see in any EM band, 300,000 years after the big bang.
Past microwave, that’s the domain of radio astronomy, with entirely different technology needed. We have huge radio telescope arrays on the ground – the atmosphere is fairly transparent to radio so there’s no pressing reason to launch radio telescopes to space, and their size would make it completely infeasible anyway, at least until some novel low-mass, self-unfolding antenna technology.
reedf1•54m ago
It's safe to say that if we are sticking a 6-ton 20ft mirror into space that the scientists probably have a reason for it...
watersb•15m ago
Excellent question!
The longest wavelengths of light are generally classified as "radio".
So radio telescopes have been tasked to explore the very early universe.
If I understand it correctly,
the "Period of Reionization" is first light we can see from processes like stars and galaxies.
There was ionized plasma at the beginning but the universe was like a really thick fog everywhere, and that first light was scattered around and you can't really see stars. As the universe expanded, that fog cooled down, and you could see, but cold matter doesn't emit much light, so there wasn't much to see. It took a while for gas clouds to collapse into the first stars, heating up the gas to ionized plasma once again, so it's re-ionized matter.
The Low Frequency Array, LOFAR, has been used to study this "Cosmic Dawn".
The Square Kilometer Array was designed to explore this era.
But! Not a radio telescope JWST has revealed unexpected, huge globs that seem to be galaxy-sized gas clouds collapsing into (maybe) black hole cores; the thermal emission from the collapse isn't nuclear fusion, so I don't know if those are "stars". But it's very early light.
Honestly, every time a new class of telescope is built, it discovers fundamentally new phenomena.
I searched "Reionization" and "Cosmic Dawn" plus some favorite telescopes via web and here using the Hacker News search (Agolia).
(Certainly you know the difference between radio and infrared, but I had to look into how those choices of telescope have observed different aspects of Reionization Era, got nerd-sniped, and just had to write it down in a couple of sentences.)
317070•41m ago
I love the finding, but I really like the first sentence on their abstract: "JWST has revealed a stunning population of bright galaxies at surprisingly early epochs, z>10, where few such sources were expected."
Unless stunning has a technical meaning I'm unaware of, I like this approach of starting a technical paper with something less dry.
belter•23m ago
In scientific writing stunning can also be used in a neutral sense to mean far outside the baseline. It does not necessarily carry an aesthetic meaning like stunningly beautiful... :-)
nasretdinov•1h ago
XorNot•1h ago
jacques_morin•1h ago
metalman•59m ago
how about you go make yourself conversant with "just" the technical requirements of the main cryogenic pump onboard, leaving out the rest of the thermal management systems for whatever remains of your life, which will have to long in order to fail honorably.
nasretdinov•55m ago
jacquesm•16m ago
So to 'catch' a certain frequency with a receiver the size of the receiver gets proportionally larger as the frequency drops. Focusing light can be done with relatively small gear. Focusing radio waves, especially when the source is distant requires a massive structure and to keep that structure sufficiently cool and structurally rigid is a major challenge. It is already a challenge for the JWST at the current wavelengths, increasing the wavelength while maintaining the sensitivity would create some fairly massive complications.
In the end this is a matter of funding, and JWST already nearly got axed multiple times due to its expense.
metalman•11m ago
Sharlin•56m ago
For far IR/submillimeter observations we had Herschel in space, SOFIA in the stratosphere (flying on a 747), and several large terrestrial telescopes at very high altitudes can also observe at FIR/submm wavelengths. But sure, there are likely many astronomers who would love nothing more than a new spaceborne FIR telescope, given that it’s been more than a decade since Herschel’s end of mission, and SOFIA was also retired in 2022.
For microwave we’ve had several space telescopes (COBE, then WMAP, then Planck), mainly designed to map the cosmic microwave background. That’s the farthest and reddest that you can see in any EM band, 300,000 years after the big bang.
Past microwave, that’s the domain of radio astronomy, with entirely different technology needed. We have huge radio telescope arrays on the ground – the atmosphere is fairly transparent to radio so there’s no pressing reason to launch radio telescopes to space, and their size would make it completely infeasible anyway, at least until some novel low-mass, self-unfolding antenna technology.
reedf1•54m ago
watersb•15m ago
The longest wavelengths of light are generally classified as "radio".
So radio telescopes have been tasked to explore the very early universe.
https://en.wikipedia.org/wiki/Reionization
If I understand it correctly, the "Period of Reionization" is first light we can see from processes like stars and galaxies.
There was ionized plasma at the beginning but the universe was like a really thick fog everywhere, and that first light was scattered around and you can't really see stars. As the universe expanded, that fog cooled down, and you could see, but cold matter doesn't emit much light, so there wasn't much to see. It took a while for gas clouds to collapse into the first stars, heating up the gas to ionized plasma once again, so it's re-ionized matter.
The Low Frequency Array, LOFAR, has been used to study this "Cosmic Dawn".
The Square Kilometer Array was designed to explore this era.
But! Not a radio telescope JWST has revealed unexpected, huge globs that seem to be galaxy-sized gas clouds collapsing into (maybe) black hole cores; the thermal emission from the collapse isn't nuclear fusion, so I don't know if those are "stars". But it's very early light.
Honestly, every time a new class of telescope is built, it discovers fundamentally new phenomena.
https://duckduckgo.com/?q=LOFAR+square+kilometer+array+reion...
https://news.ycombinator.com/item?id=44739618
https://news.ycombinator.com/item?id=46938217
I searched "Reionization" and "Cosmic Dawn" plus some favorite telescopes via web and here using the Hacker News search (Agolia).
(Certainly you know the difference between radio and infrared, but I had to look into how those choices of telescope have observed different aspects of Reionization Era, got nerd-sniped, and just had to write it down in a couple of sentences.)