a bonobo humanity?

So why is there a dark matter problem, or is there? This putative stuff apparently doesn’t interact with light. My uneducated guess is that we’ve tried to measure the mass of the universe (if we ever have) through measuring light given off by stars/galaxies and found not enough to correlate with some sophisticated mathematical theories of universal mass/energy we’ve constructed. According to the PBS Space Time guy, who always sounds super smart about this stuff, recent findings by the Just Wonderful Space Telescope (JWST) of super-massive galaxies over 30 billion light years away (don’t ask) have raised speculation about ‘dark stars’ powered by dark matter – even though these galaxies are really shiny bright. So, shiny bright dark matter – what gives? 

Well needless to say, all this raises oodles of problems. First, to make a dark star you likely need a new type of particle, one that can’t ‘interact with itself’ [particle masturbation?], which apparently is a rule for dark matter. And the PBS guy goes on:

That means one dark matter particle can’t bounce off another without getting super close. That enables dark matter to avoid collapsing easily under its own gravity, which is needed to explain how it remains as a giant puffy cloud surrounding nearly all galaxies.

Slam on the brakes, I think I’ve learned something? Dark matter forms a giant cloudy stuff around all galaxies! Or remains there, a sort of remnant? I cling to words, as I don’t know anything else. For example, I don’t really understand matter collapsing under its own gravity…

So this is how stars form… Gravitational contraction and collapse is fundamental to ‘structure formation in the universe’. First we get accretion, where gaseous matter, presumably of a simple sort (hydrogen? or proto-hydrogen?) is pulled into an accretion disc, which after reaching some sort of gravitational tipping point collapses in on itself to create pockets of density like black holes and stars. But what is this gravitational tipping point? I know I’m moving away from dark matter here. Anyway, this collapse, contraction or compression raises the temperature to the point where thermonuclear fusion occurs. But somehow dark matter avoids all that. 

Anyway getting back to JWST, it has been given a number of missions or tasks, and the relevant one here is JADES (the JWST Advanced Deep Extragalactic Survey), which is an attempt to gain as much info as possible on the first galaxies or whatever to form in the universe. JWST apparently works – by design – particularly well in the infrared section of the electromagnetic spectrum:

It can see stars whose energetic ultraviolet and visible light has been stretched far into infrared wavelengths as it travelled to us through an expanding universe. 

So I gather from that sentence that infrared is longer wavelength light, and that the expansion of the universe actually stretches the wavelength of initial bursts of radiation over space-time…

It’s estimated that these ‘dark stars’ or the radiation from them, date to a period some 400 millions years after the birth of the universe. And their brightness suggests ‘super-galaxies’, common enough in the universe, but not from way back then, because there doesn’t seem to have been enough time for them to form. So these discoveries have sent cosmologists into a spin. Here’s another interesting quote from our very interesting PBS Space Time Guy: 

After all, these are the cosmic dark ages we’re peering into, a time when the ocean of pristine hydrogen forged in the Big Bang shrouded our vision across much of the electromagnetic spectrum. It’s a time when that same pristine hydrogen was able to form stars many thousands of times more massive than today.

So there seems a slight contradiction – not enough time for super-galaxies (or super-anything?) to form, yet ‘pristine hydrogen’ could form super-massive stars. Mais, continuons. The visual with this depicts Aldebaran (I have to notice everything), a star in the Taurus constellation and one of the biggest stars visible to we near-blind humans. It’s 44 times the diameter of our sun. 

So these JWST discoveries have spawned scientific papers, of course, with some suggestion that they’re ‘super-bright dark stars’ (it’s theoretical cosmology, get over it). The theory, I think, is that under certain circumstances dark stars may form via dark matter particle annihilation. The particles are annihilated by their anti-particles – except that it’s more weird than that, as it’s theorised, in a recently published paper, that the particles are their own anti-particles, causing a process of self-annihilation. 

Clearly we don’t know what dark matter actually is – one proposed candidate is a WIMP, a weakly interacting massive particle – but if we assume, with the PBS Space Time guy, that there’s lots of dark matter in the early universe, seasoned with a fair measure of hydrogen and helium, with uneven densities, accreting and pulling stuff in as mentioned before, creating structure, possibly at gigantic scales…. Well, here’s where I’ll quote the Space Time guy again, coz I don’t really get it: 

The seeds of the first giant stars would have been so-called mini-halos with masses of millions to hundreds of millions of times the Sun’s mass. The dark matter part would have a hard time collapsing due to being weakly interacting. However the gas in that halo would fall towards the centre, perhaps en route to building a star, depending on how large this halo was. 

So, I’m not quite sure where the halo idea came from, but mea culpa. Here’s some useful info from Phys.org:

The largest gravitationally bound objects in the universe are galaxy clusters that form at the intersection of cosmic web filaments. These entities are shaped and grow through massive collisions as material streams into their gravitational pull. Within the heart of some galaxy clusters are mysterious and little known radio mini-halos. These rare, dispersed, and steep-spectrum (brighter at low frequencies) radio sources surround a bright central radio galaxy and are highly luminous at radio wavelengths.

This, so far, isn’t taking me anywhere clear, but I’ll continue on in later posts, using Canto and Jacinta as my guide… But the next post will likely be on determinism (in human affairs).

References

Did JWST Discover Dark Matter Stars? (PBS Space Time)

https://en.wikipedia.org/wiki/Gravitational_collapse

What is dark matter? – with Peter Fisher (Royal Institution talk)

https://phys.org/news/2017-08-brighten-perspective-mysterious-mini-halos.html#