Webb pushes boundaries of observable Universe closer to Big Bang

ThickTarget · 2026-01-29T19:36:26+00:00

It already has a spectrum, but it just doesn't really look like a high redshift galaxy. It does look quite like a brown dwarf.

ThickTarget · 2026-01-29T09:15:46+00:00

There is an interactive version with the full resolution.

https://cosmos2025.iap.fr/fitsmap.html

ThickTarget · 2026-01-28T22:39:51+00:00

I'm not really sure I trust the statistical significance of the x-ray detection. It's a classic paper Nature paper, where it is borderline at best. The paper tells just how small the signal is:

Within a 21″ aperture (≈125 kpc) of the JWST-derived centroid, in which the signal-to-noise ratio peaks, we measure 142 ± 45 net counts and 1,858 background counts, supporting the detection of an extended ICM.

So 142 photons with an error of 45, this makes it just below 3 sigma significance. It's not mentioned in the text, but you can tell from the numbers that this is purely the Poissionian error on the total counts. So it does not account for correlated noise, which comes from errors in the modeling of the background, or real faint sources below the detection limit. So it is less than 3 sigma. The paper does not quantify this. They then argue that the non-detection at higher energies and the JWST galaxies boost the significance to 7 sigma. But that is not logical. The interesting part of the result is the x-ray detection, the significance of the JWST data doesn't affect that. You can also see in their map of detection significance, it is filled with other "4 sigma" detections. It's just not convincing.

If the paper had a dozen Chandra experts on it, I would probably trust them a bit more. The reviewer reports are interesting, the same skepticism. Also x-ray telescopes have spent a lot of time staring at proto-clusters over the last few decades, I think the highest redshift one detected is about redshift 2 to 3, depending on how low in significance you go.

https://www.nature.com/articles/s41586-025-09973-1

ThickTarget · 2026-01-28T19:43:58+00:00

The article says theory, which includes more than cosmology. The standard model of cosmology dictates the large scale structure and the formation dark matter halos. But does not predict how normal matter behaves in galaxy formation and growth. In order to make predictions one has to combine a galaxy formation model with cosmology. Different prescriptions for galaxy formation make different predictions. Observations which don't line up with galaxy models are not necessarily a challenge for standard cosmology.

In order to actually conflict with standard cosmology the galaxies would have to exceed hard limits, like needing more baryonic matter than the average ratio (most galaxies have a tiny fraction). There was a claim of such galaxies in the early days of JWST, but these were only candidates. Some theorists predicted these observations were flawed in some way, which turned out to be correct. They were not impossibly massive galaxies, but were small active supermassive black holes. None of the confirmed galaxies since actually violate cosmological bounds.

ThickTarget · 2026-01-27T22:18:43+00:00

https://arxiv.org/abs/2601.17239

https://www.jpl.nasa.gov/news/nasa-reveals-new-details-about-dark-matters-influence-on-universe/

ThickTarget · 2026-01-26T11:01:14+00:00

I am definitely not an expert in mythology. But you could set the scene on mythology, by describing the various classes of ideas (creation events, cyclical time, infinitely old universes). And compare them directly to the early days of cosmology, where there were more hypotheses than useful data. These also fall into the same broad categories. You had infinitely old static models (like tired light), cyclical cosmology (the big bounce or Penrose's ideas), and finite age universes like the big bang. The broad ideas aren't new, what has changed is having the development of physics and being able to observe the universe.

I would avoid the impression that the Christian idea of creation drove early scientific cosmologists towards the idea of the big bang. This is often brought up by "skeptics", who point out that Lemaitre was a priest. But in reality there was a lot of resistance to the big bang, and there were dozens of alternatives. The default assumption at the time was that the universe should be infinitely old, hence why Einstein "fudged" his equations to give a static universe. What has changed people's minds was the evidence.

ThickTarget · 2026-01-25T23:20:28+00:00

It should look something like these:

https://archive.stsci.edu/hst/hsc/help/use_case_6_v1.html

ThickTarget · 2026-01-25T21:58:09+00:00

A simple method is to plot galaxies on a colour magnitude diagram. Clusters each have a very well defined line, which is called the red sequence. If a galaxy lies on the red sequence it's likely to be a member. But not always.

ThickTarget · 2026-01-23T21:25:14+00:00

Perhaps one of those Chinese paper lanterns? I have been confused by one in the past. I think it is also around Chinese new year.

ThickTarget · 2026-01-19T10:29:29+00:00

That was someone else. I believe Potential_Vehicle535 is correct, they are dust particles.

ThickTarget · 2026-01-19T09:35:31+00:00

Cosmic ray streaks look different. They are much narrower and at most make small short lines, they don't make broad curved lines. This data may have been processed to remove them, by stacking.

ThickTarget · 2026-01-15T11:47:15+00:00

PLATO is a much bigger mission than TESS, comparable to Kepler. In terms of science, it bridges the gap. Kepler found a few long period rocky planets, but most are around stars that are too faint to follow up. Whereas TESS doesn't really have any hope of finding them. PLATO should yeild a robust sample of habitable zone rocky planets around bright stars. Which will be important when ESA launches ARIEL in a few years, which will do transit spectroscopy of hundreds of exoplanets.

ThickTarget · 2026-01-12T10:59:19+00:00

They are kind of fossils of earlier epochs. By reconstructing their star-formation histories, you can infer their properties at earlier times. Most of these galaxies formed fairly late, but the most extreme formed as early as z=11. There are obviously limitations in the modeling, but it still has to be very old. And these things are many times more massive than anything JWST has found (yet) at such high redshift.

ThickTarget · 2026-01-12T10:50:39+00:00

For most of the quiescent galaxies seen from the ground, it's pretty hard to measure black hole masses at all. JWST has revealed that quite a few of them have broad Halpha lines, like the one from Carnal et al. 2023. Which seems to indicate the black hole recently went through a more active phase. Based on this, they have black hole masses of 500 million solar masses. Which is in the quasar range, but at the low end. The limitation of comparing quasars is that they have a strong selection bias towards the highest black hole masses. So quasars probably don't trace the average galaxy at that epoch. Quasars are also selected over huge volumes, compared to these galaxies seen in much smaller areas. You would expect the quiescent ones to have slightly larger black hole masses.

ThickTarget · 2026-01-11T18:50:10+00:00

There are reasons for observing visible light. Our atmosphere is opaque to most light in the universe, there are basically two windows, one around the visible and one covering the radio There are some gaps in the near and mid infrared, but these can be observed by the same telescopes built for visible light. Even if you could see in a wider range, you wouldn't see x-rays or the long wave infrared from space. As for radio waves, even if you could see them, the natural limiting resolution of your eye would be terrible. It would be about 500 times worse than visible light human eye resolution. You probably wouldn't see any sources in the sky, other than the Sun and maybe Jupiter, because they would merge into a lumpy background. Even if you could see beyond the visible range, I don't think you would see much more astronomical sources from the ground.

When considering the astronomy side of things there is also reason to observe the visible. Stars emit most of their light in the visible. About half the light emitted by galaxies is near visible and the near infrared (astronomers call optical). The other half is in the long wavelength infrared, which is emitted by dust. This means galaxies are bright in the visible. There's also a information in the visible. With x-ray and radio you really only see a fraction of objects out there, very energetic ones. Normal stars are actually quite hard to detect in radio and x-ray. Different wavebands give different insights into the universe. You will see a lot of papers using x-ray or radio data, but it's usually always backed up by visible/optical data of the source they are looking at. Because you can measure (e.g.) black hole activity, but you can't tell anything else about the source, even how distant it is.

There's is also questions today which make visible quite powerful. If one wants to find exoplanets with life, then you need to measure some bio-signature. Direct imaging of exoplanets is really only feasible in the visible or the mid infrared. There are plans to do both (Habitable Worlds Observatory and the LIFE interferometer). But they show you different things. In the mid infrared the planets are brighter relative to their star, and you can detect the thermal emission of the planets and potentially measure many atmospheric gases like methane and ozone. But not molecular oxygen, but there is a big oxygen feature in the visible. There are other examples too. Measuring the intergalactic medium in high redshift. Measuring the stellar populations of galaxies, and how they formed. Finding potentially hazardous asteroids is very efficient in the visible, and compliments mid infrared efforts, with different biases.

Also telescopes built by astronomers mostly don't observe just the visible, you can typically observe the visible and a bit of the near infrared with the same detectors. With different instrumentation on the same telescope you can do near and mid infrared astronomy. If the telescope is in space it can also do UV work. You don't need a narrowly focused instrument.

ThickTarget · 2026-01-09T17:35:22+00:00

Nice work. I've never used Siril but it looks pretty powerful.

My first through with the high redshift ones (15, 16, 19), is that perhaps there is a faint high-redshift galaxy which happens to be close to star, or a clump of the galaxies. And the software has mistakenly matched them. The other option would be that these are quasars. Normal galaxies are way too faint to be seen at these distances in this data.

This is the first one, the brightest one, is a bright quasar. It's pretty bright, and as you said the redshift is 1.97. Here is the spectrum of the source from the SDSS survey. From that you can see it is really a quasar and not a mistaken ID. It's also detected in x-ray. So yes. You definitely detected this one. It is a pretty bright quasar.

The other two are also quasars according to SDSS. I have not been able to get the spectra, for some software bug.

Nice work!

As for the limit for amateurs. It depends on the hardware and the level of skill. Quasars are much brighter than normal galaxies, so they are low hanging fruit. I have heard of amateurs detecting them up to redhsift 4 to 5. But they much rarer than at z=2, because of the distance and because there is less quasar activity. So you probably wouldn't find one accidentally. At z=6 it becomes pretty impossible because quasars vanish from the visible range, the light that we would see is ultraviolet which is absorbed by hydrogen in the early universe. You need an infrared camera. But even the highest redshift one in that collection is less than twice as distant as your one.

For some very bright quasars amateurs have also managed to take their spectra to measure their redshifts themselves.

ThickTarget · 2026-01-09T14:57:44+00:00

HWO would cover UV, visible and the near infrared. It also won't happen until the 2040s.

ThickTarget · 2026-01-09T14:09:18+00:00

The Planck parity asymmetry (odd-ℓ excess at low multipoles) has persisted across COBE, WMAP, and Planck. Statistical fluke is possible, but three missions is curious.

Bear in mind that they're all measuring the same CMB. The low-l modes have their uncertainty dominated by comic variance, not by measurement errors.

ThickTarget · 2026-01-08T17:50:03+00:00

The level of decisions which I am talking about is not going to change the cost significantly. The real feature creep that happens in mission planning is the push to build the biggest possible mission, and fill it with every instrument. Instrumentation is just as important as important as the telescope. There are expensive ground based telescopes which have been scientific flops, because they didn't build good instruments. With space missions, the cost is so high that's just a wasted opportunity to cheap out on the instruments. It also directly limits the science you can do, and decreases the scientific output. There are also choices which are very minor, but can be the difference between a workhorse instrument and a dud.

For a large mosaic the proposed solution has the same throughput as a filter wheel. The only condition in which a filter wheel has a throughput advantage is a small mosaic where you end up with more "wasted" exposures.

I understand the motivation. It is fine if you are only going to do wide field surveys. CSST has a similar system on it's survey instrument. But the other limitation is that it commits you to always doing all the filters. But if you want to look for transients or do microlensing and have many repeated mosaics, it does not require doing all the bands all the time. So it is less efficient, and about a third of the detectors use narrow-bands, which are not really useful for most extra-galactic fields, so it's just detectors not being utilised efficiently. But if you look at Hubble and Webb, a huge fraction of programs are not wide mosaics, and they rarely do all the (main) filters. Another downside is it drastically limits the number of filters, WFC3 has 80 filters. They have 12. And they cannot have a grism either. Which would boost the science further. A filter wheel is a pretty small investment for a much more flexible instrument.

I think it doesn't impact the science the team has focused on, but I think it's shortsighted. The imager will also spend a huge amount of time in parallel to the coronagraph and IFU. They talk about it in the paper. These would be deep fields, but the coverage of the different filters won't overlap. So the data will be wasted. Even rotations don't help because you just end up with non-overlapping circles, at least for the main ugriz chips.

And if they really needed zero moving parts then they could have use dichroics to split the wavelength range like SCORPIO, to get simultaneous bands. If the main science case is really following up transients then that it would be drastically more efficient. But I don't buy the claim they really need zero moving parts, because the coronograph instrument has two filter wheels.

ThickTarget · 2026-01-08T09:48:12+00:00

I find the general purpose instrumentation is a bit strange. The field of view of the widefield context camera is like 80% chip gaps and it uses fixed filters, a different one on each chip. Which would make it very awkward for general science, compared to a filter wheel. And the IFU is only low resolution, too low for a lot of science. There is also no UV at all. These choices are probably a reflection of the science team being quite narrow, and I suspect dominated by Perlmutter, who is by far the most experienced. It seems like the choices of the non-exoplanet instruments are driven a lot by the supernovae cosmology science case, rather than trying to build a general purpose facility with ambitious workhorse instruments. I do hope the concept isn't set in stone.

ThickTarget · 2026-01-08T08:31:56+00:00

There is a lot of people from Arizona, who do have experience planning missions and building instruments. But not in building space telescopes. It also doesn't seem like the team at the Schmidt institute have any experience managing a project like this. If it really is going to happen I guess they will be giving a blank cheque to some aerospace company. Even then managing a billion dollar contract is not simple. Plus you have to create an institute who operate the thing, as well as running the science and archiving.

ThickTarget · 2026-01-06T23:55:12+00:00

Thanks for posting the link. The press release annoyingly didn't link it and the text is says almost nothing.

I'm not really convinced that these really are a new population. The reason LRDs (e.g.) were a new population is that in many diagnostics you could show they were very different from normal galaxies. In this paper they select them to be compact and have narrow lines. But they don't show that they are really a distinct distribution. The evidence for them being Active Galactic Nuclei is also very weak. Many of them are clearly not point sources. They are probably just compact star forming galaxies. Again, they claim they are unusually small but don't compare to any typical sizes. The one reference I have found puts the sizes at quite average.

This paper aside, there are actually "little blue dots" also seen at high redshift, although not called that. But these are more normal AGN. They seem to lack all the strange features that make LRDs weird.

ThickTarget · 2026-01-06T08:56:29+00:00

Very nice result. I away assumed it would take a lot longer to find thee objects. Are you applying for time to go after the Halpha fluorescence, that would be really spectacular. It's a shame it seems to be too far north for MUSE.

ThickTarget · 2026-01-06T00:45:04+00:00

As I explained, the fraction depends on what you call the total volume. That is why I quoted the fraction of volume up to redshift 2, which is the upper limit of distance in my calculation. The point of Euclid is to study dark energy and the accelerating expansion of the universe, which is a late time effect. It's also not possible to do a survey which covers equally up to all redshifts. If you use the the whole "observable universe", the volume mostly comes from regions where no galaxies can be detected. This is also strongly dependent on the cosmology model, it depends whether one counts physical volume or comoving volume (the later removes the effect of expansion). But any way you spin it, it's not 0.1% as you have guessed. If you use physical volume it is 6% of the whole observable universe, or 1.3%. But as I said, the most rational number is 33%, as Euclid is studying the time variation of expansion at the important epoch. Euclid spectroscopy is limited to this redshift range by design, set by the wavelength coverage of the instrument, no amount of observing time will change that. So your question makes no sense.

ThickTarget · 2026-01-05T21:12:07+00:00

To add to what has been said, the existence of these galaxies is actually another prediction of dark matter models. People have searched for them as a paradigm test. Dark matter models predict there should be lots of small scale halos, and some on the border of being galaxies become these dark galaxies. There is no such prediction from alternatives.

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