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Nancy Grace Roman Telescope is also going to be amazing for raising new questions

and I hope the attempt to lift the Swift telescope to a higher orbit is successful

if you really want to stay on top of what is breaking astrophysics in realtime, I highly recommend following DrBecky on youtube or elsewhere, she is fantastic

* https://www.youtube.com/@DrBecky/videos

I thought I read somewhere that many of these little red dots are turning out to be nothing more than bog-standard brown dwarfs in our own galaxy that are confusing the signal. These days we have some pretty powerful agents who can read these things faster than I can, so I went and found the paper: https://arxiv.org/abs/2506.04004

It turns out that brown dwarfs are actually corrected for, so my remembrance is correct but factored in. I’m posting anyway because 1) it’s interesting and mildly relevant and 2) others might have the same “vague but unclear” recollection I had and appreciate the elaboration.

> many of these little red dots are turning out to be nothing more than bog-standard brown dwarfs

Your own paper estimates 5 to 25% may be brown dwarfs, and says nothing about whether they might be in our galaxy or not.

That’s valuable: I thought the whole thing was dismissed based on the brown dwarf explanation, this is interesting that that’s not the case.

It’s hard to keep up with all the news, particularly so given all the slop floating around. YouTube in particular seems to have a bunch of AI channels that just talk about this endlessly.

> Recent ideas suggest that little red dots could be black holes cocooned in thick gas, possibly representing a completely new type of object called a black hole star, in which the tight shroud of gas emits light like a stellar atmosphere.

Just be sure to name the members of Soundgarden on the paper.

Would you say this research is out of... Cornell?
Little red dots are my favorite new concept in astrophysics. This idea that there could be so much matter orbiting a black hole that the matter reaches sun levels of pressure which in turn starts steller fission without there being an star. Mind-blowing
Yep, it’s a super cool concept. A black hole of a given size has a finite amount of matter that it can ingest over a period of time. Trying to stuff more matter into it causes an outward pressure from essentially the friction of the swirling mass of material falling in. This radiation pressure could in theory be great enough to start fusion as would happen in a stellar core.

Also fun is that this puts a limit on the largest possible black hole we should ever see in the universe. If you assume a black hole formed a moment after matter condensed and then ingested the maximum possible from then until now, you get an upper bound for the largest possible black hole according to our current understanding of the universe. This limit is somewhere around 36 billion solar masses.

Will all matter in the universe just collapse into black-holes eventually ? It feels that way. And will all the black-holes then merge to form the Primordial Black Hole which will then explode to form a new universe ?
There was a time where Hawking's A brief history of time gave a decent overview of the universe to beginners. Does anyone know how well it holds up today and if anything better exists?
It doesn't answer your question, but I would love to read an updated version of Asimov's guide to science: https://archive.org/details/asimovsguidetosc00unse/mode/2up
Have not read it yet, but recently researched this question and came to this book as a readable overview of the latest thinking in cosmology, Battle of the Big Bang: The New Tales of Our Cosmic Origins by Afshordi and Halper [1].

The book assumes a basic knowledge of physics and cosmology so it does not spend half the book reviewing basics like many pop physics books do.

[1] https://press.uchicago.edu/ucp/books/book/chicago/B/bo244963...

Depends on how deep you want to go https://en.wikipedia.org/wiki/The_Biggest_Ideas_in_the_Unive...
I'll give a shoutout to Feynman's QED. It's approachable for anyone with high school understanding, and gives a reasonable insight into all sorts of phenomena.
Look up introductory college courses, e.g.., in astronomy. Their syllabi have your answers. Maybe it is more extensive than you want, but one or two book might be what you seek.

The very useful Open Syllabus Project collects syllabi and lists the most popular books, etc.: https://www.opensyllabus.org/

A professor's course materials may suit your need.

I went to a public lecture by Martin Rees at uni. He asked everyone who read it to put up their hand, then put it down if they understood it. He pointed to the professor of astrophysics who had invited the lecture and said "ok, you! The rest of you, no chance!"
There was never a time when a book gave the public an overview of the universe. ABHOT was so popular for being a book no one actually read, theres even an index named after Hawking due to it: https://en.wikipedia.org/wiki/Hawking_Index

Did _you_ read that book?

There however definitely was a piece of media that captured public minds and educated them about the cosmos. And that was the show Cosmos. The original of course. Not the NDT drivel.

You won't make it to the next iteration without wrapping yourself in a black hole and appearing as an anomaly to future observers.
How do we know whether we're already in one?
As observations become too numerous, it seems like it can be summarized as there now being too many possible candidate explanations. As data increases and becomes clearer, more and more things don't fit the existing theories.

What are the current theories explaining the early universe? What happened to the Big Bang? I only studied astronomy up to an undergraduate level, so I don't really know.

I imagine that various non-uniform gases were scattered around, and due to spatial distortions, those uniform gas regions clumped together, forming stars and other structures. Perhaps the expansion of space wasn't uniform either—it expanded unevenly, sometimes bulging, and when space expands or contracts, energy is generated, causing spacetime changes to shake the field, and that shaking might have created matter. Maybe the dynamic interaction between changing spacetime and fields revealed the energy stored in the field in the form of particles.

What do scientists think about this in modern cosmology? My knowledge is far too limited and I lack intuition, but reading science-related articles always excites me. Maybe it's because I still have some childlike curiosity left in me

The evidence for the big bang is generally not that if you look far enough back in a telescope, the universe looks younger, which is somewhat the layperson's confusion.

Evidence for the big bang is about measuring redshift of galaxies throughout universal history, homgeneity and thermal equilibrium of the universe and CMBR, which could only be explained by it all having been in a compressed location where it could reach thermal equilibrium at some point in the distant past.

None of that is challenged by the Webb observations about very young supermassive black holes.

In fact, the existence of supermassive black holes themselves has basically always been an unsolved problem even before Webb. The only known possible explanation (stellar collapse -> accretion -> supermassive black hole) could be ruled out even before Webb on theoretical and experimental grounds, we just have stronger evidence against it now. (To wit: if supermassive black holes form from stellar black holes by growing, you would expect to see lots of intermediate mass black holes. We see almost none. Furthermore, the process of accretion is extremely energetic, so IMBHs would be the most visible objects in the night sky. The fact we see none is doubly damning)

The mainstream position now will be big bang + some kind of primordial black hole formation during the very early stages of the universe. Work of Hawking/Penrose shows that black holes can form under generic conditions in solutions to the EFE equations. We have a general understanding of how they could come about from certain dense matter layouts in a standard GR cosmological model.

I dont think about it because my days are occupied by very specific problems. Theory of Bounded Rationality and its implications apply.
> spatial distortions

Acoustic distortions. The universe was small and dense enough for sound to travel through ‘space’, which was filled with plasma. The theory is that inflation blew up these tiny distortions to the scale of the structure we see in the universe.

With the caveat I'm summarising from what PBS Space Time and Dr Becky* say:

• Big Bang: we can only see back to surface of last scattering, i.e. the CMB, extrapolating backwards goes "???" at much the same point as it did a few decades back because we still have not unified quantum mechanics and general relativity

• CMB should only have isotope distribution of Big Bang nucleosynthesis, that hasn't changed in the last decades, dunno if that's what you meant by "various non-uniform gases were scattered around"?

• Variations in density of CMB do exist, key phrase is "Baryon acoustic oscillations", while they're very small magnitude they're also massive in distance scale, so they're how galactic clusters formed (that scale rather than stars directly): https://en.wikipedia.org/wiki/Baryon_acoustic_oscillations

https://www.youtube.com/watch?v=PPpUxoeooZk

https://www.youtube.com/watch?v=LRUTnoveZs8

• Re: "Perhaps the expansion of space wasn't uniform either": I heard about specifically "Timescape Cosmology", but a quick search says that's part of a broader category of inhomogeneous cosmologies: https://en.wikipedia.org/wiki/Inhomogeneous_cosmology#Timesc...

https://www.youtube.com/watch?v=SXg6YVcdOcA

https://www.youtube.com/watch?v=JlNVZz5D6WE

• Re: "and when space expands or contracts, energy is generated": no, general relativity does not in general conserve energy, and it is related to the curvature of spacetime. Simple example is that the photons in the CMB have much less energy to us than they did to the atoms they were emitted from**: https://www.youtube.com/watch?v=04ERSb06dOg

* I assuming I'm correctly judging the level and attention to detail they're providing, given the detail they put in and references to specific research publications. My degree is Software Engineering.

** There's also a Veritasium video about this, but to me Veritasium feels like a BBC 2 evening popular science show, so I'm not as confident about recommending it.

I took a good long look at the CMB picture, including the caption. It basically says the Universe was one big hot apparently uniform ball at one stage.

I don't know what conditions were like before that stage, but like Eric Idle says, nothing can come from nothing.

Dark energy is a horse shit name for a theory that was horse shit to begin with. The Universe is probably just inhomogeneous, like your intuition is saying.

The most exciting idea to me that JWST has bolstered is primordial black holes. Many models already predict them but JWST has provided the first good indirect evidence in the form of too-early galaxies. The models that predict PBHs predict that.

If they exist, they would not be constrained to stellar mass and above. There could be a population of little black holes floating around. Anything under the mass of a decent size asteroid would have evaporated by now but anything that mass and above would still exist.

They are a dark matter candidate, and one that doesn’t require new physics. But even if they don’t account for a significant amount of dark matter they still probably exist.

The most exciting thing about PBHs is that one or more may exist in our solar system. They might have been captured over billions of years. Finding them would be incredibly challenging, especially if they are low mass, but if we did it means we could directly examine and experiment on a black hole.

It could be something with the mass of a large asteroid but the size of a hydrogen atom. We could only find it by its gravitational effects. It would be utterly invisible otherwise unless it encountered matter and even then there might only be a tiny gamma ray flash, a nano accretion disc that lasts femtoseconds. We might also find smaller objects that appear to be orbiting nothing and find it that way.

Directly accessing one could allow us to test theories of quantum gravity and things like string theory, and maybe more. A black hole could be like a Rosetta Stone of deep fundamental physics.

The film Interstellar involved using plot magic to visit a black hole and solve physics, but this would allow it for real. It would just be an itty bitty one.

Of course if we had a black hole in a lab (or one in a convenient orbit) we could run all sort of experiments, but which experiments exactly? We will start by throwing things at it and watch, obviously, but that's unimaginative. What are the smart experiments?
How certain is the evaporation? Obviously Hawking radiation has never been observed, but is it tied in enough to other known physics that we can be reasonably certain it exists?
We could probably redirect budget for next gen particle accelerator to building an experimental platform orbiting the black hole, and get better results, right?
My pet theory is that supermassive black holes are older than the universe and they didn't grew much.
Does PBH theory also predict >1 billion solar mass black holes so early?
What could go wrong?
This comment will not contribute anything, and/but it is a thought that I had a few days ago, and I cannot 'shake' it. We keep 'discovering', recognising, mapping, etc. And I feel that every 'breakthrough' is "one step closer" (let's say 100 steps total), on a journey that is a thousand miles long. So, for the past 4000 years (or whichever century we can call the 'birth of astronomy'), we have accumulated 'this much' knowledge, and still we know a speck of sand in a vast desert, and perhaps now we have accelerated the rate of knowledge gathering, but still we are SO FAR.. ufff..
This is almost the same article as https://www.quantamagazine.org/a-single-naked-black-hole-rew...
This is one of my favorite phenomena: again in again, across various fields of study, breakthroughs in discovery allow us to go from relative ignorance to a level of knowledge and understanding that enables clear and clean conceptual models; then, as we learn even more, we realize how much more complex and weird and multifaceted reality really is.

It’s like a Dunning-Kruger effect on a field-wide scale, but in a good way. Rather than an example of hubris, it’s an opportunity for awe.

I think this can be explained by the dictum "big effects get discovered first"

It does present a weird science communication problem. After the first generation, scientists are all focused on "little effects" and don't get excited about talking about the big effects any more. They like talking about what they're working on (little effects). Textbooks drift from fundamentals and new entrants and outsiders get a distorted view of reality.

So I wonder, where are these giant black holes now? There should be some closer to us than at the edge of the universe, unless something happens to them.
The supermassive black hole in the giant elliptical galaxy M87 is merely ~53 million light years away, close enough that we have now imaged it:

https://en.wikipedia.org/wiki/Messier_87#Supermassive_black_...

Such a fun read, looking forward to more
That’s a beautiful article showcasing our predicament in having access to more information about the universe. Now i have to be the one to ask the dumb defensive question:

what makes us so certain that we can trust what we see on James Webb? Can we definitely discard a measurement problem?

JWST has 4 different instruments on it. While they all share the same focusing mirrors, but otherwise are 4 different measurement devices.

For the red dot observations, I believe this things have been measured by at least 3 of the 4 devices on board - NIRCam (near infrared camera, has very limited spectral capabilities through its filter wheel), NIRSpec (near infrared spectrograph) and MIRI (mid infrared instrument).

I cannot pretend to have the actual expertise, but it does seem vanishingly unlikely that all 3 instruments could create consistent artefacts in the same location.

Only two things are infinite: the cosmos, and a web designer’s obsession with discovering new ways to break scrolling.
Quanta magazine is a glorified university press release and marketing shop for Simons associated institutions.

Take it with a grain of salt, and know for sure its leaving out a huge range of scientists views.

Instead of questioning whether the Big Bang assumption is true, astrophysicists prefer to perform endless "gymnastics" to try to make the mounting contrary data fit their theory about how the universe began.
> Faced with observations of early black holes and galaxies that weren’t expected to exist, scientists have come up with a wealth of new theories to explain them. Now they just need to figure out which ones are true.

This subtitle really bothers me. Science isn't about finding out what is true. Science is about finding out what is false and building models to explain the rest. We can never confidently say we know something to be true because that closes the door for future science to disprove our beliefs and that's exactly the purpose of science.

The best we can do is come up with increasingly more useful models accepting that in the end all models are wrong but different models are useful for different purposes.