2023-05-11

2023-05 May Science Readings

2023 May Science Readings

May the 11th, and I have only just started. This isn't going to be a productive month.
A bit of progress by thw 18th.

Articles studied this May - some of which might go to Slashdot.
WTF is a Magrathea planet?
Thorne-Żytkow objects
Sporadic rotation in tightly-packed planetary systems
Some Tweets.
Replacing Areceibo?
The Winchcombe Meteorite.
Mantle structure below HotSpots
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I've got my keyboard better set up for accenting etc, and that's worth remembering. But it's not really a thing for this page. And I need to work on the redshift calculator (online version). [I still can't see what I was concerned about.]

Well, now I've got a problem. Why are my changes to my CSS not updating?

P …

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WTF is a "Magrathea Planet"?

ArXiv : Statistics of Magrathea exoplanets beyond the Main Sequence

Do people these days need to reference that Magrathea is a fictional planet in Douglas Adams' "Hitchhiker's Guide To The Galaxy"? Hopefully not, but if so, follow the link.

From the radio series/ books/ TV series/ films, the planet is sufficiently Earth-like for an unmodified tea-drinking slightly furry English-person to walk across the surface, picking his way between the lumps of confused sperm whale, armoured in a slightly battered dressing gown. So, essentially, Earth-like.

But what is a "Magrathea planet", according to these astronomers? Well, I'm not sure exactly how they got from the book description to a "system[s] in which the planet survived the [white dwarf] formation of the stars in the binary." In particular they're looking at planets around double-white dwarf systems, of which "No exoplanet has been found orbiting double white dwarf (DWD) binaries yet." That terminal "yet" suggests they have some reason to believe that there will be an announcement, some time "soon". Watch, as they say, this space.

There is a hint in the books etc that the Magrathea "civilisation" (Adams' own expressed doubt) is quite old in human - and "galactic" - terms. Which goes with a relatively old stellar system … there are a lot of caveats to put in there, but it's fiction, so not worth getting too bothered about. These scientists seem to have priority on re-using the term in an astronomical context, and I guess we pretty much have to accept it. They're a moderately interesting type of planet, but ultimately not going to be that common, compared to main sequence star's planets.

The "gas giant" aspect of the definition is in contradiction to Adams' earth-like scenario, but does mean the class is of relatively detectable planets. The main difficulty is likely to be in finding "DWD" systems, because by definition, they're going to be dim. The closest WD to Earth is the Sirius (absolute magnitude +1.43) and it's companion WD, ("Sirius B" sometimes called the "Pup", absolute magnitude +11.83, on a 50-year orbit about the primary) which is about 10.4 magnitudes (a factor of 14400-fold) fainter. As a "DWD" system, we certainly wouldn't have spotted tis until the 1700s, if not 1800s, while as it exists today, it's the brightest star i nthe sky after the Sun.

As a class of planets, it's a logical class, and this is a name for it. But it's not ever going to be a particularly common class, compared to those around G₀- or M- stars.

There are other science uses of "Magrathea" in software ("Magrathea-Pathfinder: A 3D adaptive-mesh code for geodesic ray tracing in N-body simulations") and experiment ("Magrathea: Dust growth experiment in micro-gravity conditions"). Both are in the field of "building planets", which was the business area of Adams' Magratheans. Which is all good fun.

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Observational predictions for Thorne–Żytkow objects

https://arxiv.org/pdf/2305.07337.pdf

Well, I had to search my note to remind me how to type the (capital-Z-upside-down-caret) character. (It's Super-.,z on my machine.) But that's not the big point. What the fsck is a Thorne-Żytkow object? Thorne–Żytkow objects (TŻO) are potential end products of the merger of a neutron star with a non-degenerate star. Ohh, so, the popular trope every time there is some science news about a black hole or neutron star, "What would happen if this entered the Solar system? is right up this street.

There has obviously been theoretical work in the past on this, because the paper doesn't start with the NS entering a photosphere. They seem to have their NS already at the core of the "non-degenerate" star ("the Sun" for the Internet wail). Previous work (1975 to 1991) suggests that Depending on the mass of the combined star, it can be supported either via nuclear burning on/or near the surface of the NS and by accretion onto the NS. Which is rather what you'd expect, if you think about it for a few seconds. The situation isn't that far from what happens to a NS in a binary system, as it accretes material from the non-compact star, except (this is important) there is enough material compressing the burning area to not go down the SNIA route of a thermonuclear "standard" candle, but it burns in a quasi-steady state. The normal scenario of a SNIa is for a white dwarf (WD) to be doing the accreting, but you could try doing it with a NS too. The difference in surface area between a WD (approximately Earth-size) and a NS (typically 3km in radius) is going to change things a lot though.

TZOs may be news to me (though I've got to say, I had wondered about the question myself, but never researched it), but they've been a subject of work since the mid-70s, have a Wiki page, and I (probably you too, dear reader, should you exist) would be best advised to read that first. A TŻO has an estimated lifespan of 10^5–10^6 years. Given this lifespan, it is possible that between 20 and 200 Thorne-Żytkow objects currently exist in the Milky Way. answers several very obvious questions. What happens then? It has been theorized that mass loss will eventually end the TŻO stage, with the remaining envelope converted to a disk, resulting in the formation of a neutron star with a massive accretion disk. Very well and good.

A candidate TŻO was proposed in 2014, and they've been linked to other classes of odd stars (Wolf-Rayet stars, RCrB variables ... ), but that attribution has been challenged with an alternative candidate proposed. There are now a ~~half-dozen~~ eight candidates, some of which are well-known RCrB variables.

From Wiki, they're also associated (potentially) with "strange" stars (in the quantum chromodynamics sense), and hence tetraquarks and pentaquarks, all of which have appeared in my reading lists over the last few years.

So, what does this paper add, now that I've dragged myself up to speed on the base phenomenon?
By using different computer models for the nuclear chemistry that would go on on the stellar core to NS boundary, this paper makes different predictions for the nuclear make up (and so, eventually, spectroscopy) of the star. And ... it's over to the observational astronomers.

I've dropped the data into the TŻO wiki page "talk" section. I've had too many snotty responses from Wikipeople to waste effort putting it in myself.

Dramatis Personae

An obvious question is, who are Żytkow and Thorne? I don't recognise Żytkow's name, but is the "Thorne" "Kip" Thorne of various GR and gravity text books? And indeed, it seems to be him. The other author, Anna Żytkow, is a new name to me. See her Wiki page.

Edit : connected to this article from Jan 2024.

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Day ‘N’ Nite: Habitability of Tidally Locked Planets with Sporadic Rotation

https://arxiv.org/pdf/2303.14546.pdf

Quite a short one here. In a "compact" planetary system - lots of planets in close orbits tight arouind a (typically) small star, it has generally been thought that the planets woulf be tidally locked - rotating about their own axis in the same time (and sense) as they orbit the star - so that one part of the ground points permanently to the star while it's antipode points permanently to outer space. A number of SF authors have used such planets as interesting locations to set their stories, including (just two I remember) "Proxima" and "Ultima" by Stephen Baxter. In a different setting, Larry Niven looks at the "star unmoving in the sky" in different artificial habitats on "Ringworld" (1970) and on the "Bowl of Heaven" (2012). Is there something about SF authors that makes them interested in "abnormal daylight hours"? Chronic insomnia and disturbed sleep patterns, maybe?

The work here is a mathematical study of the influnce of one planet upon another in such systems. The authors find a significant number of planets can interact to torque each other between locked rotation (do I need to point out that in tidally-locked couples, both bodies are actually rotating, just at the same rate?), and rotating at various rates. The transition between rotating (with respect to the star) and non-rotating can be chaotic, with periods of chaotic rotation occupying around ⅕ of the time between periods of tidally-locked rotation - which can put a reference location near the "sub-solar point", or the "anti-solar point", fairly rapidly.

Which would make for an interestingly different place to live.

Whether it's an interesting place for an SF author to drop some small furry Centaurian creatures into (with a criminally negligent pre-colonisation survey) ... well that's a question. The "chaotic rotation" doesn't mean that one day the "Sun" rises in the middle of the sky as normal, then it starts to move to the east, does that for a couple of days, then reverses to travel to the west. However the small furry Centaurians define "sunrise", "east" and "west". No, the chaos of rotation state swaps for periods of thousands of years (orbits), not on a day by day basis. With orbital periods of a few weeks, that's maybe not such a dramtic problem. And the Good Doctor himself managed at least one story with a once-in-10,000-year event ( Nightfall)

Is there much more to the science? FTFAbstract, A recent study shows the dynamical conditions present in the TRAPPIST-1 system make rotation and large librations of the substellar point possible for these planets, which are usually assumed to be tidally locked. - which is basically what I put above. Also in TFAbstract : Our findings show that tidally locked planets with sporadic rotation are able to be in both long-term persistent states and chaotic states: where rapid transitions between behaviors are present. Quasi-stable spin regimes, where the planet exhibits one spin behavior for up to hundreds of millennia, are likely able to form stable climate systems while the spin behavior is constant. Which gives the SF fraternity somewhere to set their "playground". Many studies have shown that with sufficient heat circulation in the atmosphere and/or oceans, these planets may not have a temperature dichotomy as extreme as was once thought between their day and night side It would also seem that the paper's authors have noticed the "dramatic" potential :

An illustrative example would be a planet that was previously tidally locked for a long period of time, hundreds to thousands of years, whatever is long enough that the climate has settled into a stable state. Such a planet in the habitable zone around a TRAPPIST-1-like star could have an orbital period of around 4-12 Earth days – the approximate orbital periods of T-1d and T-1g, respectively. Due to the TLSR [’tidally locked with sporadic rotation’] spin state, this planet may, rather abruptly, start to rotate, albeit slowly – on the order of one rotation every few Earth years. The previous night side of the planet, which had not seen starlight for many Earth years, will now suddenly be subjected to variable heat with a day-night cycle lasting a few years. The day side would receive a similar abrupt change and the climate state that prevailed for centuries would suddenly be a spinning engine with momentum but spark plugs that now fire out-of-sync with the pistons. In this analogy, the spark plugs and the subsequent ignition of fuel correspond to the input of energy from starlight. The response of ocean currents, prevailing winds, and weather patterns may be quite dramatic.

It's an interesting idea. Much fun to play with. The big dramtic laibility I can see is that the onset of rotation would be fairly slow, so frozen air from "dark side" is likely to be evaporating from the terminator (day/ night boundary line) as it gradually progresses into long-untouched areas ; not freshly exposed to the heat of the noon-day sun. That terminator evaporation is going to rapidly increase the heat-transporting capabilities of the atmosphere, both into the newly-lit regions and back to the newly dark regions. Which ... is exactly where the SF author can slice and dice the "science" and "fiction" parts of their business.

For perfectly good reasons, authors are very chary about receiving "interesting ideas" from the general public. Too much chance of a "plagiarism" lawsuit. Baxter suggests mailing via "c/o Christopher Schelling, Selectric Artists, 56 Planetarium Station, New York NY 10024, USA, Email: Christopher Schelling ; if his Google-fu is strong, he'll get some notification from Google that people are talking about him. Maybe. I'll see if there's any response before the end of the month. 19th - haven't heard anything yet. I'll have to get into doing the edit-before-publish thing instead of republishing as I edit.

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Some Tweets - and Toots

Hands up who loves a good B-Z reaction? No, sorry, that's unfair. Everyone loves a good - or even a bad, BZ reaction. Well, how about this one?

The Frederick lab has perfected disposal of used luminol-based ECL reagent. After the Western is developed, inject the ECL into a solution containing 10% bleach. Chemistry is awesome! pic.twitter.com/fa9z7XEQkl
— Dr. Kendra Frederick (@kendrakf13) June 14, 2018

That's not a B-Z reaction, but it is quite dramatic, isn't it? It's obviously a light-emitting oxidation reaction (10% "bleach" is a it stronger than regular supermarket bleach (my under-sink bottle says it's less than 5%), but you could get to 10% using a freezer. What are the other reagents? Byproducts or waste products from a "Western". Which is a "Western Blot Test", I think - a way of "fingerprinting" genetic material. Or, as Wiki puts it, a widely used analytical technique in molecular biology and immunogenetics to detect specific proteins in a sample of tissue homogenate or extract. Besides detecting the proteins, this technique is also utilized to visualize, distinguish, and quantify the different proteins in a complicated protein combination. That latter is pretty much where I got the "fingerprinting" idea from. This would seem to be a mixture that is used for chemiluminescent detection, but this surplus solution has clearly not reacted with the "reporter" part of the detection antibody. "Luminol" is mentioned, with this structure :

(Structural diagram of luminol molecule, a bicyclic with benzene coupled to a nitrogen-nitrogen containing ring.)

So I guess getting any supply of luminol, in an appropriate solution , then injecting it into an oxidising solution, and you should indeed get this sort of display.

P Ah, I thought I recognised that name - the compound is one that gets cited in every second "true crime" programme as the "magic blood detecting spray". The Luminol can react (briefly, but it can be photographed) with oxygenated haemoglobin in blood, producing this same glow.

Structural diagram of luminol molecule, a bicyclic with benzene coupled to a nitrogen-nitrogen containing ring.

So if I need to clean up a site from a blood splatter, a reducing agent that reacts with haemoglobin should make the SOCO's job harder. (Scene Of Crime Officer.)

Well, that's a technique I can't use after I publish this. [Shrug]

It's a fun piece of chemistry, but I doubt I'll ever have the materials to do it. If I'm ever ordering from the BDH (or Aldrich, or whoever) catalogue, I'll maybe get some Luminol, but I doubt that'll ever happen.

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The Next Generation Arecibo Telescope: A preliminary study

link

Finally nearing "up to date".

The 1960s-designed Arecibo radio telescope sufferec catastrophic failure of one of it's three support towers on December 1^st 2020. It's loss meant the loss of observational capability in three major fields

planetary science,
space and atmospheric sciences
radio astronomy

The radio astronomy work can, to a significant degree, be performed at other sites (including the recently comissioned Chinese 500m Telescope, "FAST"), but few sites have the capability to transmit high power radio signals into the sky with high accuracy, which was used for radar imaging of passing asteroids, radar mapping of Venus, and studies of the Earth's atmosphere.

Proposals are now being made for a replacement to continue astronomical observations on the site. This proposed structure uses a large number (102) of identical 13m steerable parabolic dishes mounted on a separately pointable base structure about 150m in diameter. The "base plate" would deform under it's own weight (and wind loads ; Arecibo remains in hurricane territory), which the individual dishes can be re-pointed to accommodate as the telescope tracks a target across part of the sky. (The paper doesn't say "commodity satellite base-stations" - but with over 100 required including spares, that's the industry that would probably fill the order, even if the design is specific for this job.)

This approach of "many small receivers, linked" has long been used in radio telescopy. Big, fully steerable structures like Jodrell Bank and Green Bank have to some degree been superceded by large arrays such as the Allen Telescope Array and https://en.wikipedia.org/wiki/Square_Kilometre_Array . Improvements in radio sensitivity have moved the emphasis from the "light bucket" approach to improving angular resolution by widely-spaced receivers. The ultimate end of this approach is using telescopes at opposite points on the Earth for a receiver spacing of up to 12,000km. Until, of course someone puts a significant radio telescope in space.

Part of the purpose of science papers is to provoke questions. This approach makes me think - could the operations phase of the (proposed) NGAT130 (Next Generation Arecibo Telescope-130m) be brought forward into the construction phase by mounting the first 13m dishes around the rim of the "bowl" to start doing science while the tiltable platform is built within the "bowl".

The Winchcombe Fireball—that Lucky Survivor

https://arxiv.org/pdf/2303.12126.pdf

On February 28, 2021 a bright fireball was seen over SW England, by many eyewitnesses and by a considerable number of sky-observing "fireball cameras" which allowed the rapid calculation of the fall location. The next day, 0.6kg of relatively lightly contaminated meteorite was recovered, including one bodt which fell onto a paved driveway. The number of instrumental records allowed the reconstruction of the original orbit, and also the calculation of the strains imposed on the body at the times of it's several fragmentation events. The initial mass of the meteor was estimated at 13kg, with about 4% of it's mass recovered.

The observing cameras were parts of 5 different camera networks, all 14 cameras grouped into the UK Fireball Alliance (UKFAll) (3 from SCAMP (System for the Capture of Asteroid and Meteorite Paths) ; 3 from UKFN (UK Fireball Network) ; 3 from UKMON (UK Meteor Network) ; 2 from NEMETODE (Network for Meteor Triangulation and Orbit Determination) and 3 from GMN (Global Meteor Network). Fortunately the camera networks have common standards and procedures for reporting and combining data, allowing the networks to work together in real time. Their joint PR mechanisms managed to coordinate reporting on news media so that amateurs in the fall area recognised and collected, with anti-contamination procedures, the meteorites.

On analysis, the meteorite was classified as a CM2 carbonaceous chondrite, which is a fairly uncommon type of meteorite. (Analyses continue.) The body's pre-impact orbit was moderately eccentric (e≃0.61), which with a semi-majjor axis of 2.598 AU gave an orbit that touches Earth's orbit near it's perihelion and has an aphelion near the orbit of Jupiter (0.98 and 4.18 AU respectively). The orbit was in the same direction as the Earth's, approaching it from it's trailing quarter, which lead to the relatively low impact velocity of 13.8 km/s (the Earth's orbital velocity is 18km/s, which is a more typical lower limit for impact velocity of meteors. That low closing velocity with Earth is why it experienced realtively low stresses in flight. Even so it fragmented several times in flight, each fragmentation being accompanied by a flare of the fireball.

The meteor's pre-impact orbit falls between the 3:1 and 5:2 mean motion resonances with Jupiter, which suggests how the body may have evolved its orbit before entering on it's final orbit.

What strikes me - and slightly worries me, is the number of distinct groups of fireball cameras involved. This time they seem to have had good coordination, but with recent screaming from "online communities" about "do more, do it faster, do it quicker" (Slashdot story of 2023-05-10), I anticipate it will take considerable time to tie people from this burst of enthusiasm into the necessary networks of coordination and information exchange. Then again, that noise is from "UFO-hunters", so it probably wouldn't amount to much value anyway.

Imaging deep-mantle plumbing beneath La Réunion and Comores hotspots: Vertical plume conduits and horizontal ponding zones

I forgot to save the link, but it's Open Access.Search for "Dongmo Wamba et al., Sci. Adv. 9, eade3723 (2023) 25 January 2023"

Over the last few decades the questions in deep mantle petrology have somewhat shifted from "Do hotspots really exist?" to "What is the structure of hotspots>". In the process the image has shifted from the cartoonish idea of a single jet of hot material rising from (where? That's always been a question) to play in the underside of the crust (or lithosphere - not the same thing!), creating particular melts, and causing a circular area of thermal uplift, to the much more complex ideas expressed in this 3-d seismic tomogrpahy exercise described in this paper.

For several years, a protracted sequence of earthquakes under the Indian Ocaen island of Mayotte. I thought I'd written about the Meyotte events previously - I've certainly prepared some diagrams - but if I did, I can't find it.

Short version : there have been a lot of earthquakes under the island group of Mayotte in the arm of the Indian Ocean separating Madagascar from Africa. Lots of earthquakes. Enough earthquakes to raise very real concerns about the stability of the atoll's flanks, as well as the simple risk of unadorned ground shaking.

Mayotte is a départemnt of France, so their government have to take the threat seriously. It may be unlikely to uproot the Eifel Tower, but a major earthquake (or eruption, or sector collapse) would seriously affect, or even kill substantial numbers of French citizens (and no small number of refugees and economic migrants from across the Mozambique Channel). So of course, they French take it seriously.

One part of that taking seriously has been the establisjhment of a dense array of seismographs, which assist in locating earthquakes in the body of the volcano. But it also allows the recording of changes in seismic waves from distant earthquakes which pass through and below the volcano and are affected by changes in the rock properties. This is the essence of the subject of "seismic tomography", which acquires a very thick accretion of mathematics to deconvolve the signal from the raw seismic. But that's what computers are for.

What this paper reveals is that below the SW corner of the Indian Ocean there are conduits of relatively hot, low seismic velocity rock

moving up from the core-mantle boundary …
to pool at the 1000km to 600km (depth) "low velocity zone" …
then to move up further to pool again at another "low velocity zone" …
then finally erupt (or intrude) to (near) surface

Which is fairly conventional "hotspot" theory. But there is one problem - the vertical conduits between each storage level are offset horizontally from each other by several hundred kilometres, if not more. That definitely isn't in the conventional story of hotspots.

This diagram (from Mantleplumes.org - guess their point of view!) shows - on the left panel - the traditional view of plumes ascending more or less directly from the CMB (Core-Mantle Boundary) to the base of the crust. In the right-hand panel several "low velocity zones" (LVZs) are indicated at different levels in the mantle, associated with various levels of dismemberment of subsiding plates. In contrast, the model from this Mayotte paper postulates that the same LVZs are actually conduits for horizontal movement of magma ascending from the CMB towards the surface, potentially displacing the position of the conduit hundreds or thousands of km between each level.

Figure 3 from Comoros hotspot paper - cartoon of multi-layermantle storage model

In short, the plumbing store has supplied the same parts, but they're now arranged differently.

The previous diagrams have been cartoons. Now comes the actual data, rendered as a cube of [difference in seismic velocity] versus northing and easting (I'm avoiding "latitude" and "longitude" because that could get really complex where you're comparing radii that differ by a factor of 2).

Slices of data cube - N.E,Z position coloured for delta(seismic velocity)

What do we see here? Well, it's typical geology - obviously it bears some resemblence to the cartoon (there wouldn't have been much point drawing the cartoon otherwise …), but it's also a lot more complex. The "levels" where there is horizontal melt (heat) transfer aren't level, and the "pipes" where there is vertical melt (heat) transfer aren't vertical. The "lava lamp" appearence … well, isn't the physics in both actually quite similar. It has been a long time since I had a lava lamp, but now I'm thinking that a vacuum-walled (reduce lateral heat losses) lava lamp with 3 immiscible liquids (continuum transparent; two opaque colours) would be really intereasting. I'd put a beer on it that at least one of the offices or labs of the authors has a lava lamp of some sort.

Summary

It's a much more "realisitic" feeling model. I've always been rather uncomfortable with the "cartoon" hotspot model, because the idea of such a norrow conduit persisting for so long - as well as "how the fsck do they get started?" really seemed to ask quite a lot of Earth's materials (well, any other planet's too). But the basic idea seems to have som many things going for it too. Seamount chains ; Wrightman's triple junctions ; the Yewllowstone trace under America ... it's all very tempting.

This model makes that look a lot more reasonable. It is a much more "geologically reasonable" model. "More seismic data under other complexes!" I'd really like to look underneath the incipient rift zone of East Africa - and this can't have escaped the authors either. The Yellowstone trace, OTOH would tell us a lot more about how cells (and walls and conduits) fade away. If we we're still allowed to think about basin studies and the timing of generation in petroleum provinces, this would probably get a lot of traction there.

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2023-05-01

HTML Learnings

Moved to "Study Notes" blog

2023-04-02

2023-04 April Science Readings

Well, I'm still ploughing through the backlog. But progress …

Articles studied this April - some of which might go to Slashdot.
The backlog of old stuff
A quick "Funny"
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The Backlog

I get a daily mailing of new papers, and open ones that grab my attention by the title. I've got to speed up that pipeline to get through the backlog.

What have I got open on the tab list?

The Event Horizon Telescope Image of the Quasar NRAO 530 link This isn't "new" observation with the EHT, but calibration observations made back in 2017 as part of the initial runs of the radio interferomenter. "Their observed brightness temperature suggests that the energy density of the jet is dominated by the magnetic field. " - Intensity, polarisation and position of features changes. Further observations. I think I can leave this one pending.

Machine learning detects multiplicity of the first stars in stellar archaeology data link Complex study on Population-III stars, trying to work out their multiplicty from the fine details of the metallicity of thes Milky Way's "EMP" (Extremely Metal-Poor) stars. Yes, there were probably a lot of multiple, within the same range as today. Worth testing - because these stars supernovae are likely to end up beig the oldest probes into the universe since the CMB, and we need to know (or at least, test) that the stars then were similar to those we see "today" to calibrate our models on.

The Venus’ Cloud Discontinuity in 2022 link There's some weird stuff going on in Venus' atmosphere - it rotates faster (at some altitudes - than the ground. Which is ... odd. Continuing observation campaign.

Limits on Neutrino Emission from GRB 221009A from MeV to PeV using the IceCube Neutrino Observatory link In last month's GRB221009A Slashdot posting I predicted more papers. I think this was posted to ArXiv a couple of days later than that one, and there will be more in the backlog. I commented on /. that this was a (relatively rare) negative report - "we looked for Y, which we expected to see, but didn't". Valuable, but as sexy as the Ann Widdicombe range at Ann Summers.
See also : The first JWST spectrum of a GRB afterglow: No bright supernova in observations of the brightest GRB of all time, GRB 221009A, "The host galaxy appears rather typical amongst long-GRB hosts and suggests that the extreme properties of GRB 221009A are not directly tied to its galaxy-scale environment." ; The power of the rings: the GRB 221009A soft X-ray emission from its dust-scattering halo (What formed those ring-like structures presented in the composite paper, and what we can deduce from them.) ; Implication of GRB 221009A: Can TeV Emission Come from the GRB Prompt Phase? The highest-energy particles from the source probably "probe" deepest into the central "engine" of the event, and thus the whole class of events. ; GRB 221009A THE BOAT Studies the brightness of the GRB, and justifies calling it at least the "Brightest since human civilisation began."

Galaxy Zoo stuff : Galaxy Zoo: Kinematics of strongly and weakly barred galaxies ; Reanalysis of the spin direction distribution of Galaxy Zoo SDSS spiral galaxies I know "Galaxy Zoo" - do you? (Seriously - answers in a comment below, please!) It's one of the early examples of "Citizen Science", using the bulk observations of (lightly) trained amateur observers to classify (previously-made survey) images of galaxies using the human eye-brain abilities for pattern recognition. No dpoubt it'll be replaced by AI models ... uhhh, trained on Galaxy Zoo results. That's counting "angels dancing angel-counting dances on pinheads" territory. Recursion, potentially to a worrying level.
Anyway, two papers here. The first reports a moderate, neither expected nor unexpected relationship between bar strength (contrast) and rotation speed). Peculiar, but not exactly Earth shattering.
The second is just odd. Peculiar. As determined by GZ observers, presumably not interacting, the spin direction of galaxies is fairly strongly non-random (sigma 2.33~3.97). Which ... might be some larege scale structure of the universe. Or some unexpected aspect of GZ viewers, users, or ... something. What it means I have no idea, but it's definitely not expected. Watching brief.

And that's got my "Feburary pile" cleared (with a couple of exceptions). Things to do tomorrow, but maybe get March cleared over the next couple of days.

And now it's May 11th, and I haven't touched this for nearly a month.

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Redshift calculator https://wellsite-geologist.blogspot.com/2023/02/2023-february-posting-commentary.html#Redshift Something is borked, but I didn't note what.

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Funny diving.

DiverNet job advert for people to work diving in the "storage ponds" at Sellafield.

This looks like a really fun job. I wonder if the Slashdoterati will find it as amusing?

Actually, it's probably going to be a really tedious job, with masses of paperwork and endless waiting around, taking radiation readings. But the pay would be good. Maybe. [May update : the /. editors didn't bite.]

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And that's as much as I got last month.

2023-03-28

2023-03-29 Penrose tiling for a floor

In a discussion on Slashdot, I got into a conversation with "dargaud" (who gives his home page as http://www.gdargaud.net/). He's interested in making a floor with a "Penrose" tiling - an aperiodic tiling with (if you get it right) pentagonal symmetry. So am I. The Slashdot discussion is here (search for users "dargaud" and "RockDoctor", which is me ; but this may disapear, so I've archived the relevant bit here - it's a Box link. Seems to work though).

Both of us have been looking at doing a floor with a Penrose tiling. The Slashdot report is of a single shape that can achieve this. (I missed that from the summary, when it should have been the most prominent point. But "Meh". Bad summary writing/ editing ; or the editor thought "aperiodic tiling" was something novel, which it hasn't been since the early 1970s. Whatever, hardly news on SLashdot. Bitching about the editors is something I try to avoid, but sometimes your patience bends) From comments, this singular shape includes convex and concave sections of the perimiter that enforce Penrose's "matching rules" to enforce against getting either periodic patterns, or patterns that can't be continued to infinity.

This image

(lifted from Wiki) shows the components of a two-rhomb tiling system with "matching rules" expressed as both edge decorations and surface paintings.

The way I'd decided to do it is to use these rhombs, but without the decorations. I'd have to plan carefully to get the tiling right, before removing my marks on the prefabricated tiles. Or putting the marks on the floor, I haven't decided. The rhombs have angles of 36, 144, 36, and 144° for the "thin", and 72, 108, 72, and 108° for the "fat".

My next step was to calculate the sizes for making such tiles ("rhombs", rhombuses") with an edge of 10 cm. I've lost that calculation.

… and I've just re-done the calculation, then

… plotted them up. Note - the dimensions for the laminate tile are just a guess - and I might not use laminate in any case - maybe glue lino tiles onto sheet lino, so I can include some "bodge" allowance. But the main purpose of this picture is to show the effect of tile size on wastage, and how I'd "fit" the tile size to the actual dimensions of laminate sheet (or lino tiles) to optimise usage. Even if I decide to do it with lino, the same thinking would apply. Whatever materials I use, they're not going to be free, so I don't want to buy more than I have to.

The paper that triggered the Slashdot story was from ArXiv : An aperiodic monotile. The preprint doesn't indicate submission of the paper to a journal, but that may be normal practice in maths these decades. They have a pun in their terminology - they call their shape an "einstein" - nothing to do with a cetain theoretical physicist, but from the German "ein stein", meaning "one shape", referring to the "monotile" nature of their discovery - that this shape (actually a large, if not infinite, range of shapes) can tile the plane infinitely and hierarchically (which they claim to prove means aperiodically).

The "einstein" they present however has a seeming implicit triangular grid - which is quite distinct from the pentagonal symmetry in the Penrose multi-tile examples. So already I'm less than interested in it. My inner mineralogist wants to see pentagons! Time for an illustration, I think.

You see what I mean about the underlying triangular grid? That, I would definitely not go to the effort of building - far too pedestrian.

Their dark shaded tile looks, to me, to be composed of 4 congruent sub units, irregularly arranged ; and each of those is composed of four convex (so, relatively easy to cut) "kites" which also look to be congruent. I'm going to have to read further to find out what their geometry is, but they look like Penrose's "kites" from the "Kite and Dart" constructions from Penrose on Wikipedia :

Are this paper's "kites" (they use that term) the same shape as Penrose's? The authors specifically reference Penrose's kites in their description of the history of the problem.

Their next figure also shows the underlying trigonal (or is it hexagonal) pseudo-symmetry from their tilings. The note this themselves "Finally, we have noticed that these chains seem to impart a rough hexagonal arrangement to the hats, which is particularly clear in the triangular and parallelogram-shaped structures that are surrounded by chains."

20 pages into an 89 page paper, and I've seen nothing that looks like a definition of the "hat", or indeed, it's component "kites". I strongly suspect they're "Penrose Kites", as above, but if they say so, then I've missed the statement apart from the hint noted above. They mention that their "polykite" (also, "hat? Or have I missed something?) has sides of either 1 or $\sqrt{3}$ - which is slightly worrying because I'd expect those nuimbers to come out of 30° and 60° triangles, not those with 36° or 72° angles (where I'd expect to see lengths of 1 and [ $\sqrt{5} -1$ ]. Distinguishing those by eye ... I'd need a definition. If it is a 30-60 structure though, that would go a long way to explaining the (pseudo-)trigonal symmetry. (Hey, I had to learn some MAthML!)

Working further, I get to Lemma A.1, where their kite is defined as having sides of 1 and $3$ (and since it's a kite, not a parallelogram, the sequence must be 1, 1, $3$ , $3$ . That can't be the "Penrose kite", but mut be one composed of 30°-60°-90° triangles. Which would at least make manufacturing them in large numbers relatively easy.

Figures A.8 and A.9 make the case again.

The final 60-odd pages of the paper are enumrations of possible (and impossible) neighbouring sides of the tiles, from which, I assume they can derfive their aperiodic claims.

I've no need to go further into this rabbit hole. I'm sure they've got their maths right, but aesthetically, the resultant pseudo-trigonal symmetries are not what I'm looking for. It'll be the fat-thin Penrose rhombs for me (or possibly "kites and darts", assembling those from their component triangles, which I can make by cutting strips, then cutting strips into triangles, then re-assembling.

2023-03-14

2023-02 Results of a new asteroid surface survey.

The NEOROCKS project: surface properties of small near-Earth asteroids

Source (ArXiv)

This paper reports new initial spectroscopic analyses of the surfaces of 42 asteroids. The main result for space enthusiasts is that there is not one "M" class asteroid (metal-rich) surface in the collection.

The imagery that (many) people grow up with from Hollywood and TV "science" "documentaries" is that the Solar system is full of asteroids which are made of metal ready for mining to produce solid ingots of precious metals, with which the metals markets of Earth are likely to be crashed. That's Hollywood (perhaps somewhat influenced by a number of PR companies indulging in metals market manipulation), not reality. This result is about what you'd expect from the proportion of metallic asteroids - about 0.5%.

Some other pointers : Nearly 40% of the observed NEOs (16 out of 42) are classified as PHAs. PHAs are Potentially Hazardous Asteroids. It's not terribly surprising - all asteroid surveys are going to be biased towards the bright ones - which means those that get relatively close to Earth (well … until we have significant observatory capability at (say) Earth-Sun L2 and L3). It sounds a frightening statistic, but it's not something that's going to keep me awake at night.

The asteroid mining fraternity dream of taking apart an M-type asteroid like Psyche, which is fair enough as a dream. But they are relatively rare asteroids. Realistic "ISRU" (In-Situ Resource Utilisation) plans are going to have to expect to digest around 200 silicate mineral (and clay ("phyllosilicate"), and ice) asteroids for every metallic one they digest.

I suppose I should mention that 9 of the 42 bodies fall into the broader "X" classification, which can contain "M" class asteroids with less distinctive spectroscopic results - such as asteroids with only a small amount of metal on the surface. Given the size of the set considered in this work, up to one quarter of one of the bodies observed might be metallic. Which is still not terribly good news for the asteroid miners. In reality, almost all asteroid mining is going to find (and need to use) is silicates, and probably a fair amount of "ices" which could feed a "plastics" processsing plant. If you have inherited a vision from SF of massive foundries smelting whole asteroids into "hull metal", best leave that image in Hollywood.

The NEORocks program's home page is here. One of their main aims is to focus on extremely high standards in data dissemination, and I hope this helps them.

This went up onto Slashdot at https://science.slashdot.org/story/23/03/18/0341259/small-near-earth-asteroid-surfaces-have-few-precious-metals-study-finds, but the editor ("EditorDavid") stressed the "precious metals" aspect of it, which I never considered in the least bit important. Ho hum - have to be more careful about writing things that @EditorDavid is likely to re-write.

2023-03-01

2023-03 March readings

Well, trying to get back into the habits. I've got some hangovers from December to February, but cna I fight down the backlog?

Articles studied this March - some of which might go to Slashdot.
Planetary Science - Results of a new asteroid surface survey.
Cosmology - early galaxies
Cosmology - even earlier galaxies
Cosmology - A nearby dark galaxy.
Planetary Science - Jupiter’s interior and core
Planetary Science - Habitability of planets around white dwarfs.
Cosmology - The very first stars.
Planetary Science - A nearby exoplanet at 22pc
Cosmology - Does the speed of light vary through space.
Cosmology - The Radio to GeV Afterglow of GRB 221009A
End of document

2023 March science readings.

"NEOROCKS project: surface properties of small near-Earth asteroids"

https://arxiv.org/pdf/2302.01165.pdf

This paper reports new initial spectroscopic analysis of 42 asteroid surfaces. The main result for space enthusiasts is that there is not one "M" class asteroid (metal-rich) surface in the collection.

The asteroid mining fraternity dream of taking apart an M-type asteroid like Psyche, which is a fair enough dream. But they are relatively rare asteroids. A realistic "ISRU" (In-Situ Resource Utilisation) plans is going to have to expect to digest around 200 silicate mineral (and clay ("phyllosilicate"), and ice) asteroids for every metallic one they digest.

I suppose I should mention that 9 of the 42 bodies fall into the broader "X" classification, which can contain "M" class asteroids with less distinctive spectroscopic results - such as asteroids with only a small amount of metal on the surface. Given the size of the set considered in this work, up to one quarter of one of the bodies observed might be metallic. Which is still not terribly good news for the asteroid miners. In reality, almost all asteroid mining is going to find (and need to use) is silicates, and probably a fair amount of "ices" which could feed a "plastics" processsing plant. If you have inherited a vision from SF of massive foundries smelting whole asteroids into "hull metal", best leave that image in Hollywood.

The NEORocks program's home page is here. One of their main aims is to focus on extremely high standards in data dissemination.

Regular Rotation and low Turbulence in a diverse sample of z~4.5 galaxies observed with ALMA

https://arxiv.org/pdf/2302.03049.pdf

The context is that we have models of how galaxies developed from primordial gas clouds (with or without the first generation of stars contaminating the gas clouds with (astrophysical) "metals") ... but as we're improving our IR and radio astronomy (JWST, ALMA ...) , those models are not agreeing with reality. Which Feynman had a blunt response to. This is a moderate part of that "tension" - the observed galaxies have better developed discs, reduced turbulence and more ordered structures than were expected. Not a huge amount earlier, but eyebrow raising. Another paper in the pile (next section, here) discusses observations at z ~8 which are much more challenging for the star formation and galaxy formation models.

This is a "moderate" tension result. But what grabbed me is that I tested my "Redshift Calculator" on it and got an "Age of Universe" figure for z~4.5 of 1.3 Gyr - the paper says "more than 1.5Gyr ago", which I take as "agreement", since they've got a sample of five galaxies. The corresponding age figure for observations at z~8 is 0.6 Gyr - which puts a lot more stress on the question of "how to build a galaxy, fast?"

I note that the rotation curves produced for the galaxies in this set show (figure 6) the "flat" profile of velocities rather than a simple Keplerian drop-off. As Vera Rubin deduced in the 1970s (and Fritz Zwicky saw hints at in the late 1930s), this implies that the visible galaxy is embedded in a considerably bigger, but less concentrated, disc of gravitating matter - the original "dark matter" observation.

A massive interacting galaxy 525 million years after the Big Bang

https://arxiv.org/pdf/2303.00306.pdf

Well, if the previous section discussed a … tension in astrophysics, of the form "it is awkward for our models of galaxy development to produce a well-structured galaxy in less than 1.5 Gyr", then how much more inconvenient to find evidence of a "massive interacting …" (see paper title)? That's a much worse tension. Almost any revision of models that accommodates this observation is going to make the previous section pretty much "mainstream". Which is the significance of the paper.

Abstract (highlights)

JWST observations confirmed the existence of galaxies as early as 300 million years and with a higher number density than what was expected based on galaxy formation models and Hubble Space Telescope observations.

New data, old models were wrong. Film at 11.

a high-resolution spectroscopic and spatially resolved study of a rare bright galaxy at a redshift z = 9.3127 ± 0.0002 (525 million years after the Big Bang) with an estimated stellar mass of (2.5 ^+0.7 _−0.5) × 10⁹ M_sol

Thats broadly the mass of the Milky way. And again, my redshift-to-distance-time converter is in agrement. Worth the effort invested.

The star formation rate, however is considerably higher than for the Milky Way. Which makes sense for a "young" galaxy. Similarly for the metallicity - about a tenth of that locally. Also sensible. So, the modelling tension is in the big-scale end of galaxy formation, rather than at the small end of star formation and evolution.

The system has a morphology typically associated to two interacting galaxies, with a two-component main clump of very young stars (age less than 10 million years) surrounded by an extended stellar population (130 ± 20 million years old […]) and an elongated clumpy tidal tail.

Uhhh ... well the universe was smaller then (that's what redshift means, after all) So, interactions would be expected. Tidal tails, we see "today", so that's not breaking any hearts.

Our observations provide evidence of rapid and efficient built up of mass and metals in the immediate aftermath of the Big Bang through mergers, demonstrating that massive galaxies with several billion stars are present at earlier times than expected.

My Discussion

The big contribution of JWST to previous (Hubble, Spitzer) observations this far back, is that JWST can do sufficient spectroscopy to identify "metals", and their approximate quantities. "suggesting that [we] are missing key physical processes connected to the formation of first galaxies". No doubt the popular science press will present this as "astronomers baffled" by "revolutionary data" ; the actual position and reaction is a bit less dramatic.

The remaining 50-odd pages of the paper are the technical details of how the observations were turned into astronomical parameters. I'm not qualified to comment on those details, but that's what the "peer" in "peer review" stands for.

Discovery of an isolated dark dwarf galaxy in the nearby universe

https://arxiv.org/pdf/2302.02646.pdf

This is the first substantive discovery I've seen reported from the Chinese "Five-hundred-meter Aperture Spherical radio Telescope" (FAST) - whose comissioning phase started (approximately) at the same time as the damage (then collapse) of the "thousand foot" (300-odd m) radio telescope at Arecibo, Puerto Rico after ... I've forgotten the name of the hurricane. But it was a hurricane that did it, possibly exacerbated by some botched US government responses.

The radio telescope detected a patch of hydrogen gas emission with a pattern of frequency variation consistent with it being a rotating mass (some areas rotating towards us, some rotating away). Checking against optical images of the region, the area didn't have a large amount of starlight (less than 100,000 Sun-like stars worth) while the rotation data suggested a mass of hydrogen about a thousand time larger. The redshift for the body is 0.0083, suggesting a distance of about 36.8 Mpc (Planck best-estimate cosmology ; 120 million light years).

As noted in the previous two readings, the understanding of how physics gets from the Cosmic Microwave Background to building galaxies is not well understood. We have models, but they're clearly not in good agreement with reality, so the models need to be changed. That's more in the range of changing a few parameters in a large equation than substituting four elephants on the back of a cosmic turtle as a model of the universe. But someone is going to take it as meaning that.

Someone is going to object to 120 million light years away being described as "nearby". But I'm OK with that because if they had an arbitrarily good telescope, they'd be able to see Terrestrial mammals - that's recent!

"Jupiter’s interior from Juno: Equation-of-state uncertainties and dilute core extent"

https://arxiv.org/pdf/2302.09082.pdf

The second biggest event in the formation of the Solar system (after the Sun starting to fuse hydrogen in it's core) was the formation of the core of Jupiter, rapidly followed by it accumulating most of it's mass from the gas-rich disc of material surrounding the (heating up) sun. This must have happened quite quickly, because what we see around modern very young stars is that the "lighting up" of the central star rapidly drives away the remaining parts of the molecular cloud from which it grew.

The orbit of the probe "Juno" was designed to investigate this question. While basic Newtonian theory says that a spherical mass has a very simple gravitational field, if we model Jupiter as a core of an Earth-like density surrounded by a shell of gaseous (if compressed) hydrogen, we'd get a slightly different gravitational field, particularly when the spacecraft is relatively close to the core. Which means, flying from a long way from the planet to as close as possible to the "cloud tops". The spacecraft will accelerate slightly differently in this "dive" if the core is large compared to if it is small (or non-existent). Which is part of the reason for Juno's trajectory to have been designed as long loops away from the planet, with much shorter high speed "dives" past the cloud tops. Intermediate parts of the flight path make close approaches to the various satellites.

So, how big is Jupiter's core, and how sure are we about that?

Frankly, we still don't know. Past work has suggested a core of around 20% of Jupiters mass, with possibly a diffuse upper margin. This work doesn't contradict that, but also can't confirm it, because our knowledge of the "Equation of State" (EoS, relating pressure and density) for a mixture of hydrogen, helium and some "metals" (beryllium upwards on the periodic table) isn't well enough known to confidently get an internal model from the experimental data. So, it's time to dig out the diamond anvil presses, line up the heating and measuring lasers, and get back to trying to measure those EoSs to try to wring more data from the spacecraft's observed motions.

That's the Carnegie Geophysics lab (with nearly a century of experience in such experiments ; other Geophysical labs are available), doing space science on machines designed to probe the interior of the Earth. There's something I like about that. Unfortunately, it's not a storywith a clear conclusion. Yet.

The Influence of Tidal Heating on the Habitability of Planets Orbiting White Dwarfs

ArXiv 2303.02217

Abstract

[..]we revisit the prospects for habitability around these post-main-sequence star systems. In addition to the typically considered radiative input luminosity, potentially habitable planets around white dwarfs are also subjected to significant tidal heating. The combination of these two heating sources can, for a narrow range of planetary properties and orbital parameters, continuously maintain surface temperatures amenable for habitability for planets around white dwarfs over time scales up to 10 Gyr.

That's not exactly surprising - since the first discovery of extra-solar planets (around a pulsar!) people have wondered what could happen on them. The cooling history of the white dwarfs (and pulsars) is extended, so if you can have planets form there, you might have a geological history and potentially a biological history. Adding a second, also long-lived, heat source to the planets could make that a more long-lasting situation too. Certainly worth invvestigating.

What sort of planets could survive their parent star going red giant - or even supernova? For "rocky" planets outside the actual radius of the red giant, that's not a major problem - even Earth is anticipated to survive the Sun's RG phase, unles it is actually enveloped (which is a "definite maybe". Whether the gas giants (Jupiter in particular) survive the Sun's RG phase ... and with how much mass, is an open question. One of the "plusar planets" mentioned above is thought to be a gas giant core which has been stripped of it's atmosphere leaving a carbon-rich core which might be mostly the diamond allotrope of carbon.

The presence of an outer "gas giant" (or it's core) would potentially enhance the production of tidal interactions and heating. That's my 0.10€ worth.

With regard to "pulsar planets" there's another constraint - to form a pulsar needs a fairly large star, which means a short lifetime. Estimates for the time to form a Jupiter are Order(10Myr), so any star of more than about 12.5 solar masses would go through it's catastrophic final development phases while it's planets are still forming. That's very challenging - particularly for a gas giant. Not only does the planet need to survive the heat flux from the supernova, but it is still radiating it's "heat of accretion". Very challenging for a planet to survive a supernova. Less challenging for a planet to form after a supernova in an accretion disc around a pulsar.

Time to RTFP, to see if the authors worked on it too.

Observations have demonstrated that an estimated 25 – 50% of white dwarfs have spectroscopic evidence for pollution that implies accretion of planetary material. Well, that's a surprise to me. If that is anything like correct, then it means that the distribution of planets around WDs is pretty similar to that around stars in general. Or, equivalently, the RG phase of stellar evolution is not terribly destructive to the existence of planets in orbit around the star

The basic problem of habitability of planets around white dwarfs is written in the "cooling curves" for white dwarfs of different sizes. That's an almost pure physics problem - a "spherical cow" cooling in a vacuum, where the cow really is spherical. The calculated habitability zone decreases from around 1AU at 10 Myr afteer the origin of the white dwarf, to about 0.01AU 10Gyr after white dwarf formation. That's not considering tidal heating.

Tidal heating requires non-zero orbital eccentricity or non-synchronous rotation to operate. Well, yes. On the other hand, most orbiting bodies do have non-zero eccentricity, and maintaining synchronous rotation through the orbital changes needed to stay in a "habitable zone" is going to be challenging too. It's probably safe to say that most white dwarf planets would need tidal heating to be considered in their budgets, even if it's only a minor effect. The authors also consider that for a planet to migrate from outside the area cleared by the red giant phase into the area of potential habitability, they're most likely to have done that by tidal migration, which requires significant eccentricity.

Drawing on work from the 1960s, 70s and 90s, the authors then develop some expressions for estimating the surface temperatures of planets, when including tidal heating. The addition of tidal heating can extend the duration of "habitability" by a factor of up to 10 for more moderate degrees of orbital evolution of the planet. Over a wider range of planetary parameters the duration of habitability can be increased from 1-3 Gyr to 6 to 10Gyr - which is the predicted duration of habitability on Earth. While the specifics of the calculation depend on the physical properties of the planet, we have demonstrated that tidal heating may play a critical role in the habitability of planets around white dwarfs.

Caveats

No account is taken of the atmospheric properties of the planet. It's sure to have an effect, but generally that would be to broaden the habitable zone rather than narrow it.

It is unlikely that these planets would exist in isolation. The spectroscopy shows that "planetary" material is being accreted onto the surface of the white dwarfs, so there must be a regular flow. That means, unavoidably, impacts on the planets under consideration. Whether that's a big deal or not ... nobody knows. Earth probably survived a "late heavy bombardment" during the period that life first developed (though the peak intensity and duration are in considerable doubt).

Discussion

This is a quite interesting finding telling us that we can't exclude white dwarfs from consideration as potential places to search for biosignatures (or even, "ET"). Which is OK.

The most massive Population III stars

https://arxiv.org/pdf/2302.09763.pdf

" ; really early stars, possibly visible with JWST ; when did they form, and what does that reveal?

Background : several generations ago (1926 to 1944), astronomers messed up. They noticed that some areas of galaxies had relatively blue stars and called them "Population I" (letter "capital i", not digit "one"), while more yellowish stars dominated the cores of galaxies and globular clusters, and were called "Population II" stars. That was a purely descriptive category - they could as well have been called "John", "Paul", "George" or "Ringo" - but it turned out to be age-related, with Population I stars having a higher "metallicity" than Population II stars (when spectroscopy improved through the 1950s and 60s, to measure the metal content of stars with sufficient accuracy. ("Metal" in the astrophysical sense of "any atom that isn't hydrogen or helium".) Unfortunately, the chosen labels were opposite to the direction of growth, and nobody bit the bullet of changing the terminology. So when a (then-hypothetical) class of really early stars, with extremely low (almost zero) class of stars was proposed in the late 1970s, they were called "Population III", and the terminology misfit was cemented in place. So, "Population III" stars are some of the first stars that formed in the universe. Some (low mass) ones are probably stil present today (spectroscopic surveys are in work to identify them, nearby ; to be 12+ Gyr old, they must have a mass lower than about 0.96 the mass of the Sun, so luminosity less than 0.8 that of the Sun), but this paper is about the other end of the mass spectrum.

Those high-mass stars had short lives, and contaminated the "primordial" material of the universe with it's first doses of "metals", which changed the absorbtion properties of that material so they can't easily form really big stars. But those "really big stars" also have really big deaths - supernovae, or "hyper novae" which produced (it is thought) gamma ray bursts (GRBs), maybe groups of interacting neutron stars and black holes which themselves produce gravitational wave events from their mergers, and a whole plethora of other interesting events.

Which is the context behind the paper.

As a side effect, these extreme-mass Population III stars probably seeded the super-massive black holes (SMBHs) at the centres of galaxies. SMBHs as a side-effect - that's some serious shade being thrown.

The actual paper is a development of a new method for estimating the efficiency of early-universe star formation, out of which masses of plausible Population III stars emerge failry naturally (well the authors say so, and got it past peer review ; the maths are beyond me). At red shifts of 10~20 (so dates of 180~470 Myr after the big bang) there should be Order(1,000~10,000) of these hypermassive Population III stars visible to the JWST. Which is justification enough to plan an observing programme. Whether it gets observing time in competition with the other calls on the observatory's time.

An Earth-sized Planet around an M5 Dwarf Star at 22 pc

https://arxiv.org/pdf/2302.00699.pdf

22pc (parsecs) is pretty close ; our closest star (other than the Sun) is Proxima Centauri at 1.3pc (4.24ly) away. An "M5 dwarf" is one of the commonest types of star in the Milky Way galaxy, and this report ... well the title of the paper says most of what needs to be said.

Obviously, being close-by (22pc, 71.7ly) this straight-off goes high in the schedules of telescope time to confirm (or deny) the existence of the planet, to try to find more planets, and to seek spectroscopic evidence of it's atmospheric composition (if it has an atmosphere.

With a stellar mass of about 0.16 of the Sun's mass, this system has the potential to exist for a long time. About a thousand billion years (compared to the Sun's current 4.5 billion year (Gyr) age and the universe's age of 13.27 Gyr. The planet's mass isn't well-constrained (yet - telescope time will be being booked) at 3.0±2.7 Earth masses it's not a planet with an analogue in the Solar system, but these "super-Earth" or "sub-Neptune" planets are a common find in other planetary systems. (The mass is fairly uncertain, so the plausible composition could be anything from almost pure iron to a rock-ice mixture.) That lack of an analogue is going to be a challenge to planetary scientists to interpret it's atmospheric characteristics, which in turn will greatly affect the degree of global warming the planet undergoes and therefore it's surface (and atmospheric) temperatures. The planets "year" of 4.01 days is short by our standards, but not remarkably short by the cohort of characterised exoplanets. The estimated surface temperatures (ignoring any global arming atmospheric effects is in the range 377~412 K (104~139°C) but could be within the liquid water range if the albedo (reflectivity) was high, such as a heavily clouded planet. That will give SF writers somewhere to re-settle all their stories originally set in a 1950s "Jungles of Venus" environment.

It's a nice planet, and potentially encouraging for exploration. At 22pc, it may be within reach of technologies like the "Breakthrough Starshot" programme. Since that programme would construct considerable propulsion equipment on Earth, then once the first "swarm" of fly-by projectiles is en route to it's target, there would be 20-plus years between the end of the launch programme and the first arrivals at Proxima Centauri. It would not be rational to leave those assets to rust in those intervening decades.

Do current cosmological observations hint at the speed of light variability?

https://arxiv.org/pdf/2302.00867.pdf

Varying speed of light is a popular straw for the Star Trek wannabees and the God-squad to clutch at. The bad news from this, which used the most recent data is, no significant evidence for speed of light variability (but some statistically insignificant evidence in the more distant measures, where the noise is highest.

There is a common trope that "scientists don't think outside the box". This is the sort of report that gives the lie to that claim. Scientists do look at paradigm-breaking ideas like "c can vary with time or space". But they typically find that the paradigm-breaking version of the idea doesn't actually conform with the evidence. And as everyone's favourite Nobel laureate says, "if it disagrees with experiment, it [your beautiful idea] is wrong."

Another popular "paradigm breaking" idea is that Newton's gravitational concept is significantly wrong (we know already that it's wrong in detail - that's Einstein's General Relativity ; but that collapses back to Newtonian results at low speeds, masses and fields). If it's such a "suppressed" (another common accusation) subject, how come a search of ArXiv paper abstracts for "MOND" (MOdified Newtonian Dynamics - probably the best developed alternative to Newtonian-Einstinian gravitational theory) yeilds 16 papers on the subject since the start of 2023 (as I write in mid-March). That's hardly "supression".

The Radio to GeV Afterglow of GRB 221009A

https://arxiv.org/pdf/2302.04388.pdf

This paper is probably too esoteric for Slashdot itself, but I'd not noticed GRB221009A previously. It's a helluva beast. [Wiki]

lasted for more than ten hours since detection,
could briefly be observed by amateur astronomers.
This is also one of the closest gamma-ray bursts and is among the most energetic and luminous bursts.

and occurred an estimated 1.9 billion years ago,[5] at a distance of 2.4 billion light-years away from Earth."

Redshift is given as z= 0.151 … which my calculator (something is broken on that page) gives as 1.95 Gyr look-back time, and 644.3 Mpc (2101.1 Mly) which is close enough to the Wikipedia values (they're probably using a different spacetime model to me. See the redshift discussion linked to above.

Anyway, it's a beast, and I missed it. Only 5 months ago, so the flush of results should be turning up now.

Slashdot submission

Necessary, because the editors frequently muck about with the submission, contrary to the general opinion that they do nothing.

A recent paper on ArXiv describes a Gamma Ray Burst (GRB) whose light arrived late last year as one of the strongest ever observed. GRB 221009A was detected on October 9 last year (yes, that number is a date), so 5 and a bit months from event to papers published is remarkably quick, and I anticipate that there will be a lot more papers on it in the future.

Stand-out points are :

- it lasted for more than ten hours after detection (a space x-ray telescope had time to orbit out of the Earth's shadow and observe it)

- it could (briefly) be observed by amateur astronomers.

- it is also one of the closest gamma-ray bursts seen and is among the most energetic and luminous bursts.

It's redshift is given as z= 0.151, which Wikipedia translates as occurring 1.9 billion years ago, at a distance of 2.4 billion light-years from Earth.

Observations have been made of the burst in radio telescopes (many sites, continuing), optical (1 site ; analysis of HST imaging is still in work), ultraviolet (1 space telescope), x-ray (2 space telescopes) and gamma ray (1 sapce telescope) - over a range of 1,000,000,000,000,000-fold (10^15) in wavelength. It's brightness is such that radio observatories are expected to continue to detect it for "years to come".

The model of the source is of several (3~10) Earth-masses of material ejected from (whatever, probably a compact body (neutron star or black dwarf) merger) and impacting the interstellar medium at relativistic speeds (Lorentz factor >sim;9, velocity >99.2% of c). The absolute brightness of the burst is high (about 10^43 J) and it is made to seem brighter by being close, and also by the energy being emitted in a narrow jet ("beamed"), which we happen to be near the axis of.

General news sites are starting to notice the reports, including the hilarious acronym of "BOAT - Brightest Of All Time". Obviously, with observations having only occurred for about 50 years. we're likely to see something else as bright within the next 50 years.

The brightness of the x-rays from this GRB is such that the x-rays scattered from dust in our galaxy creates halos around the source - which are bright enough to see, and to tell us things about the dust in our galaxy (which is generally very hard to see). Those images are more photogenic than the normal imagery for GRBs - which is nothing - so you'll see them a lot.

This got posted to the front page by "EditorDavid" on 2023-04-01 21:34 (Sat April 1st, oops - I should have anticipated that ; "oh dear, what a pity, never mind"), so it's probably a good time to close this page out and start April's page.

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2023-02-24

2023-02 February posting, commentary, Science notes

2023 February Monthly Notes Page

Trying to dig myself out of a pit of depression, I've got a lot of unread stuff. Doing OK on the languages front - I've started a campagn on trying to get the last two un-achieved achievements on Duolingo, since I'm well over the 2000 day streak mark. Anyway, digging through the ArXiv pile …

Articles studied this Month - some of which might go to Slashdot.
Redshift- distance - age relationship Working out distance and age from redshift.
UPDATE Duolingo Cheat Sheet Update
A discussion diverging from WEIT, on "Earth Layers"
Other stuff to read up Carry over to March.
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2023 February science readings.

Redshift- distance - age relationship, Working out distance and (light-)age from redshift.

Nomogram paper.

Just about any extra-galactic observational astronomical paper you read mentions the redshift of [whatever they're observing. It's one of the first things they do, because it's a relatively simple observation to make. Assuming you've got a telescope whose light you can defelct into a spectroscope, set the spectroscope's inlet slit across the object, get a spectrum, find some lines (that may be a bit more difficult!, particularly for the dimmer objects), work out what they are (again, not necessarily simple, they're not actually labelled, but there are tools to help) compare to lab numbers ; calculate the redshift.

Then you quote the object's distance, and how "old" the light is (how long it has been since the light entering your telescope left the object), and frequently how old the universe was when the image we're seeing was generated. Now, that's a more complicated question, in large part because the calculation also requires you to have a model of how the universe's expansion rate has changed over the period in which the light has been "in flight". And there are genuine reasons to differ over those choices.

Nevertheless, I've long harboured the wish to be able to do those calculations for myself - an implicitly to have at least a better idea of what those choices arem and why you'd make them. And that gets into some mathematically hairy territory. (Well, hairy by my standards ; I got my Maths A-level, but at S-level, I was getting lost. Maybe if I'd gone for Maths in first year at Uni, I'd have cleared what was blocking me, but I cohose to go for Stats instead of "pure" Maths, and that has been useful. Choices, choices …).

The paper linked to above reinvigorated my hope for this project. Nomograms are useful things, though out-dated in this wonderful online world. But the particular style here is encouraging - all the lines are presented parallel, so the relationship between the elements is relatively simple. Better, there is associated source code to generate the PostScript for the pages. So the problem can't be that hard. Even better - the source code allows for adjusting one of the important parameters (the proportion of gravitating material (dark matter plus bright matter) to non-gravitating inflating matter ("Cosmological constant", "Einstein's blunder", "dark energy", whatever you want to call it) making for a "cosmological model" with a useful degree of flexibility. So, back to the grindstone of trying to work out what the relevant equations are, from lots of Wikipedia and wherever else.

Several days of Wikiing and RTFPing ... and the problem really is one of integration over your model of the universe. Which is more complicated than I really want to go. So ... I investigated the several online calculators linked to from the paper. Of those four, two are dead links, and one is limited to z <e; 10. Which simplifies matters. They agree with each other to better than 1%, which is good enough for me. So I'll just do it as a look-up table. Wright's calculator (https://astro.ucla.edu/~wright/CosmoCalc.html) produces more parameters, without the z <e; 10 constraint, so I'll use that one.

Well, I've got that working adequately (to my purposes). I'll put it up onto GoogleDocs. And here it is!

Duolingo Cheat Sheet Update

Link to revised Box file, at month end.

I've been working on Duo plenty. I've discovered a tool for "drawing down" my stock of those "lingot" things which are a metric of some sort, and that's leading me to revisit some of the earlier sections. It's also prompted me to try hitting the last couple of "challenges" in the Owl's imventory.

So at month-end, I need to update the French cheat sheet - which I won't have finished by then. Also any other cheat sheets, but I'm concentrating on (re-finishing) the French course. Which also means producing (slight) entried for the earlier parts of the course. THAT's tomorrow's job - I've been finishing the Redshift stuff first.

Slightly off left of the field, I realised that I'd got my keyboard (standard EN_GB) set up with the "Compose" key mapped to "Scroll Lock" - which is itslef a 3-key composite character on my (laptop) keyboard. Re-mapped it to look at the (physical) CapsLock key, and I acquire the œŒ key, and a number of others which I couldn't get with AltGr+… (or even "…"). ·₀⁰·₁¹·₂²·₃³

WEIT, on "Earth Layers"

Nature Paper

I was writing a comment on WEIT in response to Jerry mentioning a story about discovering a "new layer of the Earth". That lead me to think how many layers I could come up with. It all got a bit too geological for Jerry's website-not-blog, but I've saved it here.

Off the top of my head, there are :

this paper's innermost core
an "outer inner" core. People have been trying to identify the core's shape for decades, but the tools available would struggle to differentiate between a non-spherical inner core, and an inner core with a transition zone to the liquid outer core. We're getting a reasonable deconvolution of arrival-time into velocities along different directions in the inner core (and other layers - it all adds to make the whole. But whether those velocity differences are the result of shape differences (it's not necessarily spherical!) or material properties, and are those materials isotropic (same properties in all directions)? After 3 years of optical mineralogy, you should be thoroughly disabused of the idea that most materials are isotropic, but that's not a common mindset.
the liquid (and probably stirred, but is it well stirred?) outer core
the D''S'' layer of high density, high velocity material at the base of the mantle (maybe the "relics" of oceanic crust slabs, after secondary reheating after subduction). Which is definitely variable in thickness, also definitely variable in velocity, and probably mineralogy.
the lower mantle - where the variations vary fairly steadily with depth, but not too much laterally. We think.
the asthenosphere (a relatively weak, "fast-flowing" layer) from about 600km up to about 300km.
the upper mantle (which may move relative to the plates above, or may be fixed to the plates)
the uppermost mantle (about 100km of material definitely welded under the bottom of plates
then the Mohorovičić discontinuity (a 2~4km/s jump in seismic velocity, very noticeable!)
then the crust proper starts - basaltic/ gabbroic under ocean basins (judging from slices brought up to the surfacce in ophiolites), an unidentified but probably also gabbroic "lower" crust under the continents and finally a granitic/ tonalitic (plus sediments) crust from between 30 and 90km depth and daylight (very dependent on local topography).

I make that 8 or 9 layers (the lower crust is fairly continuous under both continents and oceans, with only minor differences in seismic velocity, but whether it is compositionally similar ... hard question). The Kola Superdeep borehole was attempted to reach this under the Karelian Shield, and that was both record-breaking and unsuccessful. (Was this film "Superdeep" unsuccessful?). Whether you consider the Moho a layer or a discontinuity ... generally it's modelled as a distinct surface of change, but in some parameters it's "foggy", which could be a transition zone. Or multiple faults spaced by ≲λ_sound(in these rocks).

Reading The Friendly (!) Paper ... well there's not a huge amount more. By stacking multiple recordings of the same earthquake (and so, source waveform) from different stations at differing angular distances from the earthquakes' focus, to get a display comparable to CDP stacking in shallow seismography. There's some deep maths to that, but the outcome seems fairly clear. They try to get out from the data estimates of the anisotropy (fast- versus slow- directions) in the innermost core. It's not very well defined - which would argue against the occasionally-expressed "single crystal inner core" model. But maybe that will resolve with more data.

It's a nice result. Far from complete, but it does seem that seismography is homing in on an objective reality, through the mists of 5000+km of solid rock.

What is it about Croatia that produces lots of seismologists? Mohorovičić was bad enough, but this author Hrvoje Tkalčić may push me to learning how to do keyboard composition of ĉaron symbols.

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Examples of Redshift / comoving-distance (from Wiki - pinch of salt!)
Object	Redshift	Comoving distance	Comments	My estimate (really Wright's)
RD1	5.34	~26 billion light-years (present comoving distance)	~12.5 billion light-years (light travel distance)	8106 Mpc
Spiral galaxy UDF 423	1 (or 0.46)	~10 billion light-years (or 5.7 billion light-years) (present comoving distance)	7.7 billion light-years (or 4.7 billion light-years) (light travel distance)	3401 (1804) Mpc
GRB 090413	8.2	13,000,000,000 ly (4.0×10^9 pc)	Universe was 630 Myr old when happened. (Check with nomogram : gives 0.6Gyr - close accord)	9180 Mpc (and 617 Myr age)

Pages that I visit a lot.

2023-05-11

2023 May Science Readings

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WTF is a "Magrathea Planet"?

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Observational predictions for Thorne–Żytkow objects

Dramatis Personae

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Day ‘N’ Nite: Habitability of Tidally Locked Planets with Sporadic Rotation

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Some Tweets - and Toots

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The Next Generation Arecibo Telescope: A preliminary study

The Winchcombe Fireball—that Lucky Survivor

Imaging deep-mantle plumbing beneath La Réunion and Comores hotspots: Vertical plume conduits and horizontal ponding zones

Summary

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2023-05-01

2023-04-02

2023-04 April Science Readings

The Backlog

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Funny diving.

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2023-03-28

2023-03-29 Penrose tiling for a floor

2023-03-14

The NEOROCKS project: surface properties of small near-Earth asteroids

2023-03-01

2023 March science readings.

"NEOROCKS project: surface properties of small near-Earth asteroids"

Regular Rotation and low Turbulence in a diverse sample of z~4.5 galaxies observed with ALMA

A massive interacting galaxy 525 million years after the Big Bang

Abstract (highlights)

My Discussion

Discovery of an isolated dark dwarf galaxy in the nearby universe

"Jupiter’s interior from Juno: Equation-of-state uncertainties and dilute core extent"

The Influence of Tidal Heating on the Habitability of Planets Orbiting White Dwarfs

Abstract

Caveats

Discussion

The most massive Population III stars

An Earth-sized Planet around an M5 Dwarf Star at 22 pc

Do current cosmological observations hint at the speed of light variability?

The Radio to GeV Afterglow of GRB 221009A

Slashdot submission

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2023-02-24

2023 February Monthly Notes Page

2023 February science readings.

Redshift- distance - age relationship, Working out distance and (light-)age from redshift.

Duolingo Cheat Sheet Update

WEIT, on "Earth Layers"

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