2024-04-27 (Update -06-05) T CorB - a recurrent nova.

Articles studied this April - some of which might go to Slashdot.

'T' Corona Borealis (T CrB) - A recurrent nova in Corona Borealis likely to erupt Real Soon Now

T CrB - Recent papers in Arχiv.

T CrB - Distance and position on the sky.

T CrB - When ? The $64.000.00 question.

update Are We There Yet?

update 2Are We There Either?

End of document

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'T' Corona Borealis (T CrB) - a Recurrent Nova, about to recur.

This came off DrBecky's YT channel, which is good fun and well worth the effort. Another useful link is a seminar held for the AAVSO (American Association of Variable Star Observers - don't worry, unlike most Americans, they acknowledge there is a Rest Of the World) on the subject last year. Essentially, if you're a variable star observer, in the Northern hemisphere, they want you to be checking it as a regular part of your sweeps (news announcement). If you've got a spectroscopic rig on your telescope, particularly calibrated for UV spectroscopy that can detect neon lines (see seminar video), then your observations are particularly encouraged.

The last two times (or maybe 4, or 5 - there are interesting hints of pre-1800 CE observations) this star went into "eruption", it passed from well below naked-eye visibility (good binocular visibility though - it doesn't need a big scope) to about the 50th-brightest star in the sky in a matter of (at most) a couple of hours. (That's from two events, involving 4 observers - 2 discoverers, and two who were too early ; so it's a good bet for this time around too.) Thus, even if you don't catch it in eruption, yours could be the last pre-eruption brightness record - which itself is a very valuable datum.

Dr Becky and the seminar provide the details on the star ; no point in me repeating their statements here. There's a small chance of the eruption this time being a supernova (type 1-SN, even - the ones used as "standard candles" for distance measurement across the universe), which adds to the importance of understanding it as well as possible. In theory, the system could go through many of these eruptions before eventually triggering the SN - but how many ... theory doesn't have a good answer for that.

It's not hard to find - follow the full length of the handle of the Plough asterism ("Big Dipper" in America - as if "dippers" were more common implements than ploughs ; odd that) from the Plough-share, through the "wedge" of Boötes (with red Aldebaran at the tip of the wedge) but not as far as the "Square of Hercules" ; Corona Borealis is the semi-circle of stars between Boötes and Hercules. Get to know what the area looks like. When the system "goes", there will be a new star there. (At the time of writing (2024 Apr. 27.55056), the AAVSO reported a brightness of 10.034 - which means it hasn't "gone" yet. When it goes, it'll make it to about magnitude 2. THe AAVSO website above lets you interrogate their database (but please don't melt their servers if you hear of the eruption having started - scientists and actual contributors will need it - unmelted!)

Here is a "finder chart" of the area (astronomical convention : bigger blobs = brighter stars). The field of view is 15 degrees square, so your fist at arms-length will approximately cover the arc of stars comprising the Corona Borealis and the target a finger's width to the south (away from the Pole Star !? ) from the semicircle of the "Northern Crown".

Get used to what this part of the sky looks like. Some time this year, for a week to 10 days, it's going to look visibly different. Just maybe, you'll be able to see it by daylight. The constellation is about circumpolar from the UK, so you should be able to see what is happening without checking your clock first. Which includes the state of the clouds.

I missed an important point. Going on past events, the eruption will last between a week and 10 days.

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Recent papers in Arχiv.

Obviously, I should look at what has recently been published on Arχiv about T.CrB. And, to my surprise, it's already in my search history. What do we have ?

I should note that the naming is a little lax. The "T CrB" ("identifier" in "constellation") code is variably capitalised. The star has different names in various catalogues as well, but "T CrB" is concerned with the variable star. The HD catalog name (for example) might be used if you were working specifically on the (relatively) normal star, not the variable in the system. But if you were looking at the position (does it wobble?), you might look at the GAIA catalogue entry.

Arχiv references encode the year, month and sequence-within-month as "YYmm.sequence". So you've got the date in the reference.

Recent additions to Arχiv concerning the recurrent nova T.CrB

Code	Title	Comment
https://en.wikipedia.org/wiki/Nova#Recurrent_novae	Nova	Wiki article on recurrent novæ. Includes a list of the known recurrent novæ.
https://en.wikipedia.org/wiki/T_Coronae_Borealis	T CrB	Wiki article on T CrB
https://arxiv.org/search/?query=T+CRB&searchtype=all&source=header	Arχiv search	Returns a list of 128 results (today ; this will change).
arXiv:2312.04342	Accretion in the recurrent nova T CrB: Linking the superactive state to the predicted outburst	The 1946 had a dip then a brightening of about 1mag in the years before the 1946 eruption, and similar trends have been seen in 2023, leading to the current expectations.
arXiv:2308.13668	The recurrent nova T CrB had prior eruptions observed near December 1787 and October 1217 AD	Discussed in the "webinar" referreed to above.
arXiv:2307.00255	The "super-active" accretion phase of T CrB has ended	More discussion of the recent changes.
arXiv:2207.14743	Stringent limits on 28SiO maser emission from the recurrent nova T Coronae Borealis	Looking for signs of "mineral dust" being cooked by the variable star.
arXiv:2009.11902	Increasing activity in T CrB suggests nova eruption is impending	This event has been expected for some time!

The blue entry above adds context in the Abstract, with my [annotations] :

T CrB is known to display the SiO [basic unit of silicate minerals] fundamental vibrational feature at 8μm. [microwave radio signal] When the anticipated eruption occurs, it is possible [possible!] that the shock produced when the ejected material runs into the wind of the red giant in the system may be traced using SiO maser emission.

So ... they're measuring the "quiet" state signal (nothing much visible) so they can compare any "eruption" state signal to the measurements already "in the can". "We find no evidence for such emission." is useful "negative" science.

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T CrB - position on the sky and range.

Up in the main message, I described how to find the object "on the sky" :
- follow the full length of the handle of the Plough asterism ("Big Dipper" in America - as if "dippers" were more common implements than ploughs ; odd that) from the Plough-share, through the "wedge" of Boötes (with red Aldebaran at the tip of the wedge) but not as far as the "Square of Hercules" ; Corona Borealis is the semi-circle of stars between Boötes and Hercules. And don't forget - on previous "eruptions", the star became about the 50th (to 30th) brightest on the sky, for a week and a bit.

That's not quite the complete story. For fullness you'd normally also want to know the range. People tend to get (unduly) worried about potential big explosions in our backyard.

The Wikipedia page (link above) cites a report from the GAIA team of a parallax of 1.2127 ± 0.0488 mas, which equates to a distance of 802 parsecs (± 30 parsecs) or 2598.48 (± 97) light years.

Which is close enough for me to think it interesting, even if it's not quite far enough to be convincingly safe. But a strongly beamed explosion ... could be interesting. The results of the eruption could be very interesting.

Back to Article List.

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When ? The $64.000.00 question.

When making predictions, the "when" bit of the prediction isa always important. When the star entered it's "active" phase (as seen about 1938 to 1946) in 2016, fingers were pointed at 2024. When the star entered the brightness dip (see the "seminar" in the man section) phase, the date was revised to 2024, May, with a ± of about 0.5 years (6 months). We're currently nearing the mid-point of that range, but no updates on the expected time. So ... weeks to months, possibly days to hours. I'll check the figures again when I submit this to Slashdot. (Checked for brightening on JD 2460428.55208 = 2024 Apr. 28.05208 mag 9.905 ± 0.0052 - not Gone yet!). Saved submission in this blog, to see how the editors mangle it. The "check for brightening" string should be pretty unique.

Back to Article List.

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UPDATE Are We There Yet?.

So, has it gone yet?

I check the AAVSO site every so often. (And I deliberately don't provide a direct link, to avoid melting their servers.)

2024-05-10 22:25 +000 (my clock)

  Star 	JD 	Calendar Date 	Magnitude 	Error 	Filter 	Observer 	Collapse All Expand All
	T CRB 	2460440.933050 	2024 May. 10.43305 	9.976 	0.003 	V 	CSEB 	Details...
	T CRB 	2460440.931128 	2024 May. 10.43113 	9.969 	0.003 	V 	CSEB 	Details...

It hasn't gone yet. Does it's light curve show any interesting features (in the last couple of days)? (I only ask for the last couple of week's worth, and just the commonest bands. Server melting, plus response time.

There were a few reports of enhanced brightness (visible magnitude up to about 8, R band up to about 7) a few days ago, but that looks like noise. Not "Gone", yet.

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End of Document
Back to List.

UPDATE Are We There Yet?.

It hasn't gone - YET

But today's check of the AAVSO site was interesting.

2024-06-05 14∶25∶09 BST (my clock)

It hasn't gone yet. But ... I'm sure that the brightness oscillation is increasing in both frequency, and amplitude. Which is a pretty good sign of something that can't go on much longer without something breaking. That's a "model-free prediction" - whatever the forces involved are, something is going to break at some point.

Are we approaching a turning point in the B luminosity (blue curve above, representing usig a blue-transmitting filter when estimating the magnitude ; "visible" is no flter (apart from the inherent slight colour of the glass) ; red and green as obvious, but with specified standard filter ranges)? And if so ... will the star "go at the turn around in the B curve? Or at the maximum slope of the B? Or will the B just never start to slow in it's brightening?

"Isn't it Exci-e-ting ... to lose a little weight!?"

(stolen from Flanders & Swann)

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End of Document
Back to List.

Edited for some tyops, and putting links to the Arχiv papers.

2024-01-10 Cosmology Nomograms

pre { font-family: "Major Mono Display", monospace; white-space: pre-wrap; } /* keeps wrapping within container. Remember to use
where necessary. It will wrap and respect [newline] characters. */ Cosmology Ruler Bookmark"Dole, 2024) and Paper-and-pencil cosmological calculator (Pilipenko, 2013)

Separated by a number of years, these two authors have come up with rather similar ideas about how people can rapidly get an approximate answer to the fairly involved question of what an observed redshift means in terms of when the redshift was imposed on the light signal, and thus limits on when the light source was active.

The impression is sometimes given that a redshift can be directly recalculated into the age of the event(s) concerned (before today) and the time after the Big Bang at which these events occurred.

That's not the case. In fact you need to integrate a model of the cosmological universe, with matter density (and it's changes, and the inferred degree of deceleration ; "dark matter" and "bright" matter), the increasing amount of positive acelleration from "dark energy" in the recent parts of those events, and the Hubble constant at this time (which also changes with the inferred matter density changes). All of which is a fairly complex calculation, which no reasonable person can be expected to do in their head, on demand.

Both of these authors have come up with ideas about how to get reasonably accurate answers to such questions in real time. To those of my generation who grew up with (just) slide rules and log tables, not calculators, their solutions will be familiar, but to generations who grew up with digital computers everywhere, these analogue computers might seem a little odd. But when you're looking for an answer accurate to 2 or 3 significant figures, this sort of solution can give you that answer faster than you can enter the parameters into a calculator - assuming you have already set up the calculation method after looking up the procedure.

Nomograms are a way of recording the interrelations between several parameters which are linked by one or more equations. A simple graph (mathematical sense, not computing/ networks sense) is a relationship between two parameters, typically expressed as "x" (the independent variable) and "y" a "function of x" (or "f(x)" in a more recent notation) which you'd read off the other Cartesian axis. Or if you used polar coordinates, you'd link the parameters by a "radius" and an angle compared to the axis. Different expressions of the same underlying relationship. Well, nomograms are a way of interlinking three or more variables, in a way that can't really be done without a 3-d printer.

A nomogram is a way of linking several variables into one expression or an equation. You set out a graduated line to reperesent one variable - on which the user chooses a point for their value for that parameter (the graduation also implise a range of validity for the underlying equations, which are frequently approximate solutions). A second line (graduated differently, and not necessarily straight or parallel to the first, and also incorporating limits of validity) represents a second parameter of the equation, and typically the user then projects a straight line from those two points to intersect a third line on a graduation - which is the solution to the equation represented by the lines, thir angles, and the scales. You can generalise the system to more complex networks of lines and scales, allowing you to handle 4-parameter systems and higher.

The reader may recognise the slide rule as a particular form using several parallel lines, scales linearly, logarithmically, reciprocally, and with various trigonometrical functions. For several centuries, they were the scientist's analogue calculator of choice, for calculations accurate to 3 or possibly 4 significant figures. For greater accuracy, you'd need to use tables of functions, which would go up to 8 significant figures (by which point, they were bookshelves, not tables). My generation always carried a set of 4-figure logarithmic and trigonometrical tables with our science and maths text books.

All of which is background you can no-longer assume the present generation will understand. They need this to understand how to use either the nomograms or the "bookmarks".

Both presenters provide several ranges of z (redshift) to allow for use in the nearby universe (z less than 1), the intermediate universe (z between 1 and 30) or the very early universe (z greater than 10). There is recent "news" about a galaxy being found at redshift of 11.6 ; it's the current record holder, but it will be overtaken eventually.

I'm not going to reproduce the nomograms here. They're intended for a page printout sitting in your desk-tidy. Get the paper linked to above, and print the relevant pages. Better if you've got a laser printer and card or plastic stock to make them more hard-wearing, but they're not high tech.

The bookmark you might be able to use on-screen. It includes it's own scale, but if you "roll your own" cosmoligy thoughts, you'll probably find it a handy reference. One side covers z from 0 to 30 (the modern universe, linearly) and the other side covers z from 0.1 to 1000 (the early universe, logarithmically). In addition to the obvious z, age, and lookback time (how old the universe was when the redshift event happened), there is also a scale of angle per kiloparsec (which I think you'd use for planning observation campaigns to have a good probability of finding a good number of examples of [whatever you're hypothesising].

This image is scaled for 100dots per cm, and should fit onto a 30cm-wide printing area. Or you can scale it to fit your screen.

1	6	7
2	5	8
3	4	9

2024-01-09 - GNUASTRO: VISUALIZING THE FULL DYNAMIC RANGE IN COLOR IMAGES

Arχiv paper.

It has taken a decade or so for the wider world to get acquainted with (if not necessarily comfortable with) the "HDR" extensions of the JPEG format as an option for image storage and display. But JPEG was always - by decision - intended for low-quality "consumer" imaging devices - those which used an 8-bit resolution for their Red, Blue, and Green pixel values. During the whole of it's existence, there have been higher-quality sensors available, though typically not in "consumer"-grade equipment. As an example (raised in O'Reilley's ink-on-dead-tree "book" on the PNG image format, back when that was new and only intermittently supported), medical images constructed from MRI scanners and X-ray sensors routinely used 32-bit pixel resolutions (as the astronomical standard "FITS" file format is designed to use). Today, 12-bit and 14-bit precision detectors are an advertising feature in "consumer-grade" astronomical image sensors, and eventually that will work it's way into the wider imaging world.

One response to this has been the "High Definition Range" extensions to the JPEG image format. Which I stopped looking at when faced with choices over "colour gamut" and "encoding format", and I realised the field was in the middle of a format war - a minefield I did not wish to pogo-stick through. I have a depressing habit of picking the losing side in format wars (just ask my VL-bus SCSI interface card!)

Whether or not that format war is over, the more restrained field of technical imaging has a new entry for display of high-dymanic range images. From the point of view of point'n'click photographers of pretty pictures, it's probably not of much interest - because of the way it treats the low-intensity parts of the image - but for imagery with both high brightness objects (e.g., stars, or a band on stage) and low-brightness objects (e.g. nebulosity surrounding the star, or people in the audience of the band) in the same image, it presents the low brightness parts of the image with a stretched brightness while retaining the colour information in the high-brightness parts of the image.

The software is provided under the GNU General Public License (version 3 or higher if you perform any modifications). I'd expect to see it appearing in astronomy equipment driver programmes in due course, and possibly migrating out into more general image processing in due course.

For image formats, comparison images are normal. In deference to Hubble, and COSTAR, they present an image of Messier 51, the "Whirlpool Galaxy" (which Hubble imaging was itself a reference to the pen and ink drawing by William Parsons from 1845 - arguably at the start of astronomical imaging). Their first image is a recent survey image, with the R, G, and B channels displayed unweighted:

Their caption describes it as a "traditional colo[u]r image, where the background regions become black."

The centres of the two interacting galaxies are saturated - whatever pixel values are recorded in the file data, the visual image does not display the tightness of the nebular condensations. There is a hint, in the black background, of "tails" of material ejected from the galaxy's interaction.

Their caption describes this as "modified weights of the channels balance to obtain a bluer image". This is how the Hubble "first light" (and COSTAR "fixed light") images were presented. There is a strong contrast betweewn the (relatively) old stars of the galactic cores, and the relatively young populations in the spiral arms.

Given the sensitivity of human visual systems, this is the sort of presentration commonly presented to the public. But it remains the result of combining images taken through red, green and blue filters, and is not the only image that could be taken of an object, given the five filter-slots typically available in an astronomical imager. The filters chosen here correspond, reasonably well, to the sensitivity of the human eye's normal three visual pigments

The careful observer will note that the yellow "interaction tails" of the galaxies are now even less visible than in the unweighted image. That is why astronomers don't smash all their image channels into one, but keep them distinct in the FITS file format, then choose how to present them in their viewer.

The paper's caption is "gray background color image; this is the default mode of astscript-color-faint-gray. The separation between color, black, and gray regions are defined from surface brightness cuts (see text) of the G-channel (rSDSS). The use of the gray background colormap reveals diffuse low surface brightness structures that would otherwise remain unveiled."

And indeed, the "low surface brightness" of the galaxies interaction tails becomes considerably more visible. The authors also note that the "cut" between using the "colour normal" and the "inverse grey" scaling is set at a low level on the green channel.

The final image uses the normal (for astronomy) replacement of a human-compatible channel with one taken through a different astronomical narrow-band filter (this one happens to be in the red at 660 nm - which is radiation released by the Hydrogen-α energy transition, though they use it to replace the "green" human-compatible channel.

Their caption is "colo[u]r image using the Hα narrow band filter (J0660) for the intermediate (G) channel instead of rSDSS. The use of this filter reveals interesting features such as the star-forming regions that are shown in green. This also reveals some structure within the cores of the galaxies.

Another feature also intrudes - a routine problem with astronomical imaging : in the image "north-west" there is a linear feature which only appears in this channel. This is most likely a near-earth satellite which crossed the field of view while the chip was exposed through the Hα filter. Astronomical sensors are designed to be sequentiallt exposed under an external filter (R, G, B, Hα there are hundreds if not thousands in use), while consumer grade chips expose either parts of their pixel array permanently under R, G, or B filters, or alternating rows of pixels under strips of filter. Naturally, this reduces their sensitivity and pixel count by a factor of 4 - which "consumer grade" sensors can accept, but astronomers don't - hence the single-channel artefacts. Yes, this can reduce sensitivity in rapidly-changing events, but that isn't too common a problem in astronomy, and the long-established astronomical habit of taking many short-exposure shots and electronically "stacking" them mitigates this. But it is a factor astronomers take into account when planning observations. And when planning observing strategies for "Targets Of Opportunity" (TOOs) such as a gravitational wave event reported near the line of sight of a "light bucket" telescope - when the operators will slew to the TOO to take a series of pre-planned images to cover the available sensitivity and detectability gamut.

It is unlikely that this new image display format will intrude into the general public's party pictures any time soon. But astronomers, people reading astronomy papers, and possibly the surveillance industry, are likely to see it more frequently. The built in ability to customise the "cut-off" level in both channel and intensity will take some getting used to.

It strikes me - this is not unlike the visual effect called "solarisation" - which has been played with by artistic photographers since the late 19th century until the death of darkrooms in the late 1980s - and may still be in use by some artistic photographers to this day. They might like to play with this too.

Spacecraft control - Perigrine / ULA mission

A very brief thought here, in the context of the poorly-contrlled "Perigrine" spacecraft recently launched by the ULA/Vulcan mission.

wouldn't the most likely place for a leak be, in the isolation/ throttling valves from tank to motor, which would restrict the possible (plausible) thrust vectors a lot, and hence the acceleration vectors on the spacecraft? Or are they thinking that launch vibration has fractured a piece of pipe (or a fitting) somewhere, with an unpredictable vector? In which case, venting the tank through the (more predictable vector) nozzle would at least reduce the uncontrolled vector available from the uncontrolled leak?

I don't really want to get into spacecraft design, but having had to design and build more than a few plumbing systems for [multiple] gases from [multiple] tanks to [multiple] consumers, the obvious (to me design is to have an isolation valve on each tank, leading to a manifold for each gas, then a line from each manifold to each consumer, with an isolation valve on each of those lines. Throttle valve downstream of each isolation valve.

So, anything other than a break in the tank-to-[1st isolation valve] is controllable by at least one valve. And even a leak in that section can be mitigated by using all the consumers, throttled to counterbalance the uncontrolled leak, and depressurising the tank as fast as is safe. The list of "consumers" (attitude thrusters) includes counteracting pairs, so you can ramp those to the maximum, to negligible effect on the overall directional vector.

I guess I'm either going to have to get into spacecraft design (is my design's component count too high?), or drop this. But it intrigues me, and takes me back to designing gas plumbing networks for mud logging units 36 years ago.

Update - 2024-Jan-17

Last night I noticed a couple of messages on MPML: (Minor Planets Mailing List, https://groups.io/g/mpml/topics)

From: [redacted]
Date: Mon, 15 Jan 2024 03:22:13 GMT

It seems peregrine has stopped leaking and is following a (mostly) newtonian 
orbit. My slightly-over-2-hour arc suggests an impact somewhere in South America 
in the morning of January 17 UTC (around 10:00 give or take a couple hours). The 
orbit is currently too uncertain to even say if it will impact in the Atlantic, 
Pacific, Brazil, or Peru, but it seems it's definitely somewhere around there 
along a line at 10-12 degrees south.

Orbital elements:  Peregri
[SNIP Orbital elements and observations]
  
Re: Peregrine observations?
From: [Redacted]
Date: Mon, 15 Jan 2024 04:41:53 GMT

Hi Sam,
Good to see some more data.
Astrobotic has posted about the upcoming re-entry :
https://www.astrobotic.com/update-17-for-peregrine-mission-one/
Based on the data I've seen (combined with yours), I expect it to come in about a 
day later, somewhere around latitude 10 south. It does still show a bit of odd 
motion. I'm reluctant to say much about longitude until we see more data and the 
fuel runs out. The uncertainty in re-entry time and longitude are linked; if 
you've got a one-hour uncertainty in time, the earth gets to rotate 15 degrees 

more or less. However, it shouldn't take much more data to get a precise 
re-entry time/location.

Not living in the area, and having no exceptionally tall hats ... has anything happened? I'm not seeing anything on the news. The operating (and owning) company's website has an update that the lander has passed apogee (furthest point, "apo-" from Earth ("-gee") and is currently 183,000 miles from Earth. (That's a bit over a quarter million km in real money.) So I guess the second estimate for impact - Friday-ish is looking more likely. So I'll takem my extra-tall hat off then.

The Press Release doesn't estimate a landing date.

Hmmm, the [code] tag on Blogger doesn't do what I expected. Ah, I should have been using a [pre] tag pair. [pre] also being block-level, not inline. ... now I need to force line-breaks.

Update - 2024-Jan-19

On Wednesday, Astrobotic published an update describing their mission-terminating strategy combining a series of short main engine burns, and attitude adjustment to control the drift induced by the leak. This resulted an a landing ellipse between New Caledonia, Fiji and Vanuatu. (For the geographically challenged, that's in the south west Pacific.) Quoting a landing ellipse to 6σ sounds a touch optimistic for a spacecraft with an attitude-affecting leak.

On Thursday (2024-01-18) they published another update with an image taken of their target :

(They describe some of the issues involved in planning imaging, when the spacecraft is no longer on it's planned trajectory : The first attempt to take this photo yielded an oversaturated image, with the Sun making the image too bright to see the Earth. As a result, the team precisely slewed the spacecraft to reposition the Sun to be hidden behind the thin payload deck strut just to the left of Earth, which produced the starburst effects on the vehicle and revealed the Earth’s crescent. This image is completely unaltered.) And just for entertainment, I'm trying the "rotate" option. If that works on Blogger. It did. So why did I have a note that it didn't?

But the ROTATEd DIV has a bad effect of laying out beyond the area of the post.

But will it lay out beyond these paragraphs? YES, it overprints them. I need to figure that out properly. I turned the ROTATE off. They're still flag-washing, I see. As if one's nation were anything to be proud of.

2024-01-05 Hydrides in Sub-Neptune Exoplanets

Last week I noticed a paper about the "Outcomes of Collisions between sub-Neptunes", noting that sub-Neptunes (not defined in that paper, but around 5~10×M_⊕ and < 3×R_⊕) have rather different collisional properties to terrestrial properties, due to their thick, gaseous atmospheres.

This paper ("Stability of Hydrides in Sub-Neptune Exoplanets with Thick Hydrogen-Rich Atmospheres") reveals another aspect of these planets, which have no analogues in the Solar system.

The question might be asked, why are these called "sub-Neptunes", not "sub-Uranuses"? After all, Uranus is less massive than Neptune (86.8 vs 102 ×10²⁴kg). But Neptune is smaller than Uranus (R_≆=49528 km vs R_≅=51118 km). There is clearly an interior-compression process going on (described as a "radius cliff"), and Neptune is well inside the effect, while Uranus may or may not be. (Another "radius cliff" is thought to occur in planets larger than Jupiter, going up into the "brown dwarf" star range, though the "turn-over" radius is somewhat uncertain.)

This paper describes another effect which probably does not happen in the Solar system. At least, not outside diamond-anvil high pressure machines on Earth. The bottom of the hot hydrogen-helium atmosphere can interact with silicate minerals in the planetary core, potentially reducing some of the silicates (and their component metal ions) to release metals. Iron (present as Fe²⁺ in fayalite (iron-olivine) can be directly reduced to Fe⁰_metal by interaction with the hydrogen. It is less clear if the magnesium in forsterite (magnesium olivine) can be reduced to magnesium metal, but it seems that a magnesium-iron hydride Mg₂FeH₆ is possible. Water (H₂O) is a minor byproduct, which might accumulate at the top of the rock/ metal core, or might diffuse up to the atmosphere to freeze out at a high level.

The work is experimentally difficult, because at these temperatures (3000 K +) and pressures, the hydrogen makes the diamond cells brittle, while also making it interfere with X-ray diffraction to identify the products before they decompose on decompression. Raman spectroscopy does support the presence of Mg-H bonding though.

The new "hydride" phases, and possibly water-derived compounds in the hdyrgen could lead to a more gradual radial change in properties in these planets, which further work on Neptune might detect, in the same way that Juno's recent close orbiting of Jupiter has suggested it has a "diffuse" core-atmosphere boundary.

Sub-Neptunes are an interesting type of planet - sufficient justification in themselves to go out into the galaxy.

2024-01-08 The Implications of Oumuamua on Panspermia

ʻOumuamua. So much to extract from so little.

That initial mark isn't a diacritic "backtick", though it's often presented as such, but a distinct Hawaiʻian letter ʻokina, Unicode U+02BB, decimal 699. To a linguist, it's a "phonemic glottal stop"., and the recommendation in new work is to use the UNICODE character in preference to the apostrophe or "backtick" diacritics. The correct (HTML) orthography is (all one word) "& #x2bb ; Oumuamua".

We have 1I/ʻOumuamua from 2017, and 2I/Borisov from 2019. So why not 3I/XXX? Yet. I maintain a watching brief on the Minor Planets Mailing List (MPML, and have done since ʻOumuamua. There hasn't even been a pulse of excitement with a first-report suggesting a significantly hyperbolic trajectory, even if it were later dis-confirmed. Nada. Zip. Zilch. Which isn't suspicious - yet - but it is getting just a touch nervous-making, because ... well, how did Fermi put it? "Where is everyone?"

This sounds like it's an advance in panspermia theory. It is - but not in a good way if you think that panspermia is a useful idea. The authors use the number (1) and size of ʻOumuamua (≈ 100m) to estimate numbers for the total number of impact events, and the total collision mass, then re-work that to estimate the number of (potentially) life-bearing particles to impact Earth between it's origin and the palaeontological origin of life, and from that to it's importance on a galcatic scale. Which is basically, a bog-standard panspermia argument. And their figure : assuming 10⁹ Earth-like planets in the Galaxy, order of 10⁵ of them might have been seeded by panspermia. One in ten thousand. I stil think that might be a bit optimistic, but it's a lot more realistic than some of the calculations done by other panspermia fans.

Panspermia remains a practically useless idea. Given that even with panspermia, somewhere has to be the origin of life, all that panspermia does is move the question of how life originated from here, under conditions compatible with the history of Earth's environment to an unknown location, with an unknown history of environmental conditions. Which, as useful ideas go, is damned-all a useful idea.

I propose Optimi-Panspermia : wherever your organism proposing panspermia lives today, the planet where it's panspermia origin is had conditions like the worst planet in the system (for Earth/ Solar system, would that be Neptune, Eris, or Mercury?), and then the dispersed panspermia seeds had to get to the Earth-analogue planet, then immediately adapt to the new conditions and take over. That sounds a credible panspermia to me. And it has no more evidence for it than any other panspermia proposal.

Sorry, did I sound like a fan of panspermia for a few femtoseconds there? Sooooo misleading.

2024-01-05 HTML learnings for this month

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Contents

HTML notes and learnings

Table alignment

Item 2

End of document

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HTML notes and learnings

So, I'm getting a bit ... ticked off with clicking the "open in new window" option on Blogger's "add link" dialog. So ... I should be able to put ' target="_blank" ' into the CSS style header for my "a" link. No? Need to check on a different page!

OK, well I tried that - at least simplistically with 'a {target:"_blank";}' in the "style" header block . Didn't work ; page opened in the same tag.

Now, why didn't it work?

Table fidding

Do I have unstructured ways to add a comment to a table. Or would a caption do? I've got "caption-side: bottom;" set in the style sheet.

I set up a TFOOT line below the TBODY section, including a TR with COLSPAN set to occupy the whole table.

I need to find a better way to set columns to R-align - better than cell-by-cell, at least. (Stack-Overflow suggests CSS of ... Which looks workable. But it's complicated. It's easier to change the default to , because that's what I'm going to use most often. And it's mucking up updating. Or is the system just broken? This is getting horribly complex - and not working with the big table in the MOND post.

Nope, I don't understand this. Yet.

Back to Contents.

This post is probably going to grow "Contents" and sections. It's a more incremental concept.

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Table Column styling

Working on the MOND table, I realised that I hate the (default) left-alignment of tables. I need to find a way to make this.column left-aligned, that.column right-aligned, and other.column centered. Something better and more manageable than setting EVERY cell.

So, what I'm wanting is something like :

H1	H2	H3	H4
1	2	3	4
2,1	2,2	2,3	2,4
3,1	3,2	3,3	3,4
4,1	4,2	4,3	4,4
F1	F2	F3	F4

But every line is of the form : ..tr....td style="text-align:right"..4,1../td....td..4,2../td.. ..td style="text-align:center"..4,3../td.. ..td style="text-align:left"..4,4../td..../tr..
which is undesirably verbose.

StackOverflow has a question that suits, and an answer:

<colgroup> <col> <col style='text-align:right'> </colgroup> <tbody> <tr [...] then "if you look at the MDN [Mozilla Developer Network] docs for <col>, you find this: "Do not try to set the text-align property on a selector giving a <col> element. Because <td> elements are not descendant of the <col> element, they won't inherit it."

So, I think I need to go down the "define my own classes" route : HTML isn't rendered by column, it's rendered by rows. That's why there ,,tr..,,/tr.. (table rows) exist, but ..tc,,../tc,, (table columns) do not. That being said, the easiest way to style a column in HTML, is by applying the same CSS class to every ..td,,../td,, in the given column. You can type in the same class to every one manually, or you could write it programmatically, via javascript or a server-side script.

So I need a worked example of defining, say, three derived classes : td.l, td.c, td.r (TableData.Left, etc). This multiply-linked solution seems specific for 4-column tables, with the 3rd column R-aligned. Ungood, I think.

What I think I'm going to try is

1. define an extension to td (possibly also to th, for completeness?) "td.l", which inherits td's properties but adds "text-align: left;"
2. similarly "td.r" and "td.c"
3. then set up rows of [blah] td.r td.r td.c [blah]
4. Which isn't as elegant as I'd like, but if the alternative is having to write whole new sets of table definitions for every instance, may be good enough.

Testing (pretty-aligned)

Right	Centre	Left
r	c c	llll
rRRRR	c CCCC	LLLll
rRR	c cCCC	lLLL
rR	c cCC	lLLll

OK - I'm getting somewhere now. I need my own class in the STYLE header (wol.td.c etc), then have my own "td class=..." in each row. Which is still 8 more characters than I'd like per element, but it's getting better. Unfortunately, while it seems to be legal, it's not having the desired effects.

Nope, still too much burying data in presentation. Just stick to the long-winded method - it's little worse.

W3.CSS approach.

https://www.w3schools.com/w3css/w3css_tables.asp has a way of "classing" centre- or left- aligned table cells. But their implementation ends up with code like "<th class="w3-right-align"> Points</th>" ... which in itself isn't so great. BUT it does only need setting in the header they assert. OK, "imply" in the first level demonstration ; I checked and it's untrue. It needs setting on every cell. No benefit.

Back to Contents.

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Foot - I still need to fix the image size problem.

End of document

2023-01-04 First new, shorter post : the state of MOND research.

Short, single topic post.

These posts were getting really long - and therefore daunting to undertake. Maybe doing shorter, single topic posts will be easier.

New Year, New MOND data

A personal itch, being scratched in public

On a regular basis one hears assertions that "Big Science suppresses non-standard theories" - often followed up by "Free energy" schemes, Climate change scepticism, Anti-vaccination screeds and the like. It's a feature particularly of Slashdot, but more generally of the Internet. If I "did" Facebook, I'd probably cite them too. Kooks are everywhere and are vocal, and they love a "my voice is being suppressed" narrative.

So, a few months ago, I conducted an (admittedly crude) survey of a "controversial" idea in "non-standard" science using Arχiv. It was nothing complex (I searched for various terms ["Mordehai Milgrom", "MOND", "Non-Newtonian Gravity", "MOG", "Dark matter" in Arχiv's database (anywhere in article title, abstract, or body text, or figures) from Jan 01 to Dec 31 for each year, recording the counts. And now, it's time to update the numbers. They're not good reading for the conspiracy-of-suppression" theorists (well, is any reading good for them? It's not as if they like actual evidence).

Date of search	Mordehai Milgrom	MOND	Non-Newtonian Gravity	MOG	Dark matter
1991 - 2001-12-31	75	1072	735	180	43348
2001-12-31	4	38	46	16	3404
2002-12-31	2	12	13	2	693
2003-12-31	1	22	17	2	765
2004-12-31	1	12	20	2	885
2005-12-31	2	35	22	2	1005
2006-12-31	2	35	27	4	1068
2007-12-31	2	49	24	2	1179
2008-12-31	3	61	20	3	1329
2009-12-31	4	51	23	6	1635
2010-12-31	5	50	38	4	1586
2011-12-31	4	60	35	5	1643
2012-12-31	5	42	23	6	1765
2013-12-31	6	56	33	3	1802
2014-12-31	3	58	33	8	1986
2015-12-31	3	40	33	5	2123
2016-12-31	6	51	32	6	2150
2017-12-31	2	55	39	17	2239
2018-12-31	3	48	35	16	2231
2019-12-31	4	55	34	8	2419
2020-12-31	3	51	46	19	2525
2021-12-31	2	43	47	9	2651
2022-12-31	4	63	44	11	2836
2023-12-31	4	85	51	24	3429

How long is it since I made a snide comment about conspiracists and their data aversion? Too long. See table above. For those who aren't familiar with the field, "Mordehai Milgrom" is a prominent researcher in "modified gravity" ; "MOND" is a popular theory of "modified gravity" ; "MOG" is a different such theory ; "non-Newtonian Gravity" is more general term for the field ("Newtonian Gravity" being the "Big Science" conventional theory in favour of which all the other theories are being suppressed for (whatever) reason(s) ; "Dark Matter" is just there for a marker of overall theoretical activity in astronomy.

Lots of data. Would a picture help?

Much clearer. Publications in these two particular theories of non-Newtonian gravity have continued to happen at comparable rates to general astronomical activity, though the relative popularity of these two theories varies a little, "MOG" having picked up in the last few years. Mr (Professor? Probably.) Milgrom continues to publish at a fairly consistent rate - which isn't so surprising, since he's been doing so for about 40 years.

That's not the sign of a field of research that is being "suppressed", "forced underground", or even "harmful to researcher's careers". It's a sign of a relatively unpopular topic within a field. Now, "unpopular" may not be a particularly nice state to be in (anthropomorphising "theories"), but it's not a sign of effective suppression. Effective suppression is samizdat publication on midnight press runs, and the occasional publisher's head boiled in tar and spiked over the entry gates to Physics & Astronomy Departments pour encourager les autres (a short-form Voltaire-ism [Candide, ch.xxiii]; the long form is darker than many people realise.)

Having done the leg-work, I'll continue to update the data file yearly (until I get bored). If you think I should be looking at different data, that's what the "Comments" are enabled for.

Back to Contents List.

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