Weekly Update from the Open Journal of Astrophysics – 10/01/2026

Posted in OJAp Papers, Open Access, The Universe and Stuff with tags , , , , , , , , , , , , , , , , , , , on January 10, 2026 by telescoper

Welcome to the first proper update for 2026 from the Open Journal of Astrophysics. The New Year brings us to Volume 9. In many countries, especially in Europe, Christmas is celebrated on January 6th so this week was also affected by the holiday season. Nevertheless, since the last update we have published four papers, bringing the number in Volume 9 (2026) to 4 and the total so far published by OJAp up to 452.

The first paper this week (and of course the first of 2026) is “A targeted, parallax-based search for Planet Nine” by Hector Socas-Navarro and Ignacio Trujillo (both of the Instituto de Astrofísica de Canaria, Spain). This article describes a targeted search for the hypothesized Planet Nine in the outer solar system, using parallax position shifts. No credible candidates were found within the observed field. It was published on Tuesday January 6th in the folder Earth and Planetary Astrophysics. The overlay is here:

You can find the officially accepted version on arXiv here and the announcement on Fediverse here:

Open Journal of Astrophysics

New Publication at the Open Journal of Astrophysics: "A targeted, parallax-based search for Planet Nine" by Hector Socas-Navarro and Ignacio Trujillo (Instituto de Astrofísica de Canaria, Spain)

doi.org/10.33232/001c.155004

January 6, 2026, 7:53 am 1 boosts 2 favorites

The second paper is “Going beyond S8: fast inference of the matter power spectrum from weak-lensing surveys” by Cyrille Doux (Université Grenoble Alpes, France) and Tanvi Karwal (U. Chicago, USA). This was published on Wednesday January 7th in the folder Cosmology and Nongalactic Astrophysics and it presents a new framework to extract the scale-dependent matter power spectrum from cosmic shear and CMB lensing measurements, revealing a consistent suppression in the matter power spectrum in galaxy-lensing. The overlay is here:

The official version of the paper can be found on arXiv here and the Fediverse announcement here:

Open Journal of Astrophysics

New Publication at the Open Journal of Astrophysics: "Going beyond $S_{8}$: fast inference of the matter power spectrum from weak-lensing surveys" by Cyrille Doux (Université Grenoble Alpes, France) and Tanvi Karwal (U. Chicago, USA)

doi.org/10.33232/001c.155045

January 7, 2026, 9:30 am 1 boosts 2 favorites

Next we have “Constraining the Stellar-to-Halo Mass Relation with Galaxy Clustering and Weak Lensing from DES Year 3 Data” which is led by G. Zacharegkas et al. (Argonne National Laboratory, USA) and has 102 other authors too numerous to list by name from many institutions around the world again too numerous to list by name. It presents a framework to analyze the relationship between a galaxy’s stellar mass and its dark matter halo mass, using data from the Dark Energy Survey. The findings align with previous results. This paper was published on Thursday January 8th in the folder Astrophysics of Galaxies. The overlay is here:

The official version can be found on arXiv here and the Fediverse announcement is here:

Open Journal of Astrophysics

New Publication at the Open Journal of Astrophysics: "Constraining the Stellar-to-Halo Mass Relation with Galaxy Clustering and Weak Lensing from DES Year 3 Data" by G. Zacharegkas et al. (Argonne National Laboratory, USA) and 102 others based in numerous countries.

doi.org/10.33232/001c.155046

January 8, 2026, 10:20 am 1 boosts 1 favorites

Finally for this week we have “Distance measurements from the internal dynamics of globular clusters: Application to the Sombrero galaxy (M 104)” by Katja Fahrion (University of Vienna, Austria) and 9 others based in Spain, Australia, UK, USA, Brazil, Germany and Switzerland. This was published on Friday 9th January (yesterday) in the folder Astrophysics of Galaxies. This study uses the globular cluster velocity dispersion method to measure the distance to the Sombrero galaxy, finding it to be approximately 9.0 Mpc away. The overlay is here:

The officially accepted version can be found on arXiv here and the Fediverse announcement here:

Open Journal of Astrophysics

New Publication at the Open Journal of Astrophysics: "Distance measurements from the internal dynamics of globular clusters: Application to the Sombrero galaxy (M 104)" by Katja Fahrion (University of Vienna, Austria) and 9 others based in Spain, Australia, UK, USA, Brazil, Germany and Switzerland.

doi.org/10.33232/001c.155146

January 9, 2026, 9:30 am 1 boosts 2 favorites

That concludes the update for this week. I will do another next Saturday.

Leave a comment »

Greenland’s Icy Mountains – William Topaz McGonagall

Posted in Poetry with tags , , , on January 9, 2026 by telescoper
Photo by Jean-Christophe Andru00e9 on Pexels.com
Greenland's icy mountains are fascinating and grand,
And wondrously created by the Almighty's command;
And the works of the Almighty there's few can understand:
Who knows but it might be a part of Fairyland? 

Because there are churches of ice, and houses glittering like glass,
And for scenic grandeur there's nothing can it surpass,
Besides there's monuments and spires, also ruins,
Which serve for a safe retreat from the wild bruins. 

And there's icy crags and precipices, also beautiful waterfalls,
And as the stranger gazes thereon, his heart it appals
With a mixture of wonder, fear, and delight,
Till at last he exclaims, Oh! what a wonderful sight! 

The icy mountains they're higher than a brig's topmast,
And the stranger in amazement stands aghast
As he beholds the water flowing off the melted ice
Adown the mountain sides, that he cries out, Oh! how nice! 

Such sights as these are truly magnificent to be seen,
Only that the mountain tops are white instead of green,
And rents and caverns in them, the same as on a rugged mountain side,
And suitable places, in my opinion, for mermaids to reside. 

Sometimes these icy mountains suddenly topple o'er
With a wild and rumbling hollow-starting roar;
And new peaks and cliffs rise up out of the sea,
While great cataracts of uplifted brine pour down furiously. 

And those that can witness such an awful sight
Can only gaze thereon in solemn silence and delight,
And the most Godfearless man that hath this region trod
Would be forced to recognise the power and majesty of God. 

Oh! how awful and grand it must be on a sunshiny day
To see one of these icy mountains in pieces give way!
While, crack after crack, it falls with a mighty crash
Flat upon the sea with a fearful splash. 

And in the breaking up of these mountains they roar like thunder,
Which causes the stranger no doubt to wonder;
Also the Esquimaux of Greenland betimes will stand
And gaze on the wondrous work of the Almighty so grand. 

When these icy mountains are falling, the report is like big guns,
And the glittering brilliancy of them causes mock-suns,
And around them there's connected a beautiful ring of light,
And as the stranger looks thereon, it fills his heart with delight. 

Oh! think on the danger of seafaring men
If any of these mighty mountains where falling on them;
Alas! they would be killed ere the hand of man could them save
And, poor creatures, very likely find a watery grave! 

'Tis most beautiful to see and hear the whales whistling and blowing,
And the sailors in their small boats quickly after them rowing,
While the whales keep lashing the water all their might
With their mighty tails, left and right. 

In winter there's no sunlight there night or day,
Which, no doubt, will cause the time to pass tediously away,
And cause the Esquimaux to long for the light of day,
So as they will get basking themselves in the sun's bright array. 

In summer there is perpetual sunlight,
Which fill the Esquimaux's hearts with delight;
And is seen every day and night in the blue sky,
Which makes the scenery appear most beautiful to the eye. 

During summer and winter there the land is covered with snow,
Which sometimes must fill the Esquimaux' hearts with woe
As they traverse fields of ice, ten or fifteen feet thick,
And with cold, no doubt, their hearts will be touched to the quick. 

And let those that read or hear this feel thankful to God
That the icy fields of Greenland they have never trod;
Especially while seated around the fireside on a cold winter night,
Let them think of the cold and hardships Greenland sailors have to fight.

by William Topaz McGonagall (1825-1902)

2 Comments »

Exam Time Yet Again

Posted in Education, Maynooth with tags , , , on January 8, 2026 by telescoper

The January examination period at Maynooth starts tomorrow (Friday 9th January), so I thought I’d do a quick post on the topic of examinations. First of all let me wish the very best of luck to everyone at Maynooth or elsewhere taking examinations in the next few weeks. I hope at least that the exam halls are nice and warm! Actually, owing to the Sport Hall being unavailable for this examination period owing to building work, some exams will be off campus; my first exam paper is actually being sat in the GlenRoyal hotel.

Here’s a video produced by Maynooth University to remind those taking exams of some general points about preparation and, most importantly, to look after themselves before during the examination period. It’s directed at Maynooth students but students from elsewhere may find useful tips in it.

I completed the last of my revision sessions today but, as the first examination for which I have responsibility is not until Monday 12th, I’ll have to wait to find out how any of my own students have done but let me take this opportunity to pass on a few of my own tips more aimed at students in Physics:

  1. Try to get a good night’s sleep before the examination and arrive in plenty of time before the start. This is especially important when there’s bad weather that may disrupt travel. It is your responsibility to get to the examination on time!
  2. Read the entire paper before starting to answer any questions. In particular, make sure you are aware of any supplementary information, formulae, etc, given in the rubric or at the end.
  3. Start off by tackling the question you are most confident about answering, even if it’s not Question 1. This will help settle any nerves.
  4. Don’t rush! Students often lose marks by making careless errors. Check all your numerical results on your calculator at least twice and – PLEASE – remember to put the units!
  5. Don’t panic! You’re not expected to answer everything perfectly. A first-class mark is anything over 70%, so don’t worry if there are bits you can’t do. If you get stuck on a part of a question, don’t waste too much time on it (especially if it’s just a few marks). Just leave it and move on. You can always come back to it later.

Readers of this blog are welcome to add other tips through the comments box below!

1 Comment »

Ashes to Ashes…

Posted in Cricket with tags , , , , , , on January 8, 2026 by telescoper

I woke up this quite early this morning but when I checked the cricket scores I discovered that the Fifth Ashes Test between Australia and England at Sydney had already finished. Australia wobbled a bit chasing a modest target, but won in the end by 5 wickets and thereby won the series 4-1. I think that result is a fair reflection of the performance of the two teams and Australia thoroughly deserved to retain the Ashes. England’s victory in Melbourne, on a difficult batting surface, prevented a whitewash and gave them a Test win for the first time since 2010, but none of the other matches were particularly close run. In terms of attendances it was a very successful series – the five days at Sydney broke the record – but the quality of the cricket was very variable, and Australia taking a 3-0 lead after three games made the last two Tests feel rather irrelevant.

It was a particularly disappointing series for England, who must have thought they had a better chance of winning than for a long time. Australia were without key players, especially Josh Hazlewood and captain Pat Cummins (the latter only played one Test). On top of that, England captain Ben Stokes won four of the five tosses. Winning the toss at Sydney, as Stoke did, could have set up an interesting contest had England scored enough runs when they batted first (although they lacked a world-class spinner who could have won the match). Call me old-fashioned, but one of the things I enjoy best about cricket is seeing a high-quality spinner in action. Australia didn’t have one at Sydney either, Lyons having been injured.

England of course had their own injury difficulties during the tour, losing two fast bowlers in Mark Wood and Jofra Archer early in the tour. Of the replacement bowlers, Josh Tongue looked the best – and most likely to take wickets in Australian conditions – but Stokes seemed reluctant to let him open the bowling.

As it turned out, Mitchell Starc (Man of the Series) led the second-string of Austalian bowlers extremely well. It is also worth mentioning Michael Neser, a bowling all-rounder who has played for Glamorgan, who stepped into the breach and doing well with the ball. Other Glamorgan Australians Marnus Labuschagne and Usman Khawaja did not have such a successful series; the latter has now retired from Test cricket.

Jamie Smith playing an idiotic shot against the bowling of Marnus Labuschagne

I didn’t see much of the cricket – only highlights – but it seems to me there was a crucial difference in the fielding. England dropped far too many catches, including easy ones, while Australia held onto some stunners. England’s batters also had a tendency to play stupid shots at important times. I’m thinking primarly of Jamie Smith’s dismissal off the innocuous bowling of Marnus Labuschagne, which was calamitous, but there were others. Above all, though, I think the first few matches revealed England’s preparation to have been completely inadequate. Questions should be asked not only of the squad selection but also of the management of the tour, especially the lack of practice matches.

On the bright side (for England), Joe Root scored his first Test century in Australia and then scored his second. Jacob Bethell who is only 22, scored a fine century in the final Test at Sydney. I’ve read articles praising him, but didn’t see much evidence in the stats to justify their opinion. Now he’s shown what he can do in the Test arena, I wonder if he will turn out to be a successor to Root?

Anyway, that’s the Ashes done and dusted (so to speak). By the time of the next Ashes series Australia (2029/2030) I will have retired. Although I’ve been to Sydney, I’ve never visited Brisbane, Perth, Adelaide or Melbourne. Now there’s an idea…

P.S. I was slightly surprised that Mitchell Starc was Man of the Series. Travis Head scored 629 runs, which was to my mind even more impressive. Still, this award is ample compensation:

Travis Head named the Beard of the Ashes series

2 Comments »

Now you REALLY need to leave X (and so does your employer…)

Posted in Uncategorized with tags , , , , on January 7, 2026 by telescoper

I have written many times (e.g. here) about the reasons I left the social media platform X, formerly known as Twitter. I quit Twitter in August 2023 and have no regrets for doing so. I have more followers and better engagement on Bluesky and Mastodon than I ever had on Twitter, and far less abuse. Unfortunately, my employer, along with most public institutions, still maintains an account there, a position I find ethically indefensible. Not to put to fine a point on it, I find it outrageous that Maynooth University persists in using Xitter. Touting for trade in a far-right propaganda channel is no way for a institution of higher education to behave. I’m very disappointed that I have only heard of a few organizations that have taken the principled decision to leave. You can read more about my views on this matter here.

My opinion on this has hardened considerably with the revelation that the AI bot known as Grok, which is integrated with X/Twitter, has developed a facility for creating nonconsensual and sexually explicit deepfake images, including pictures of children, for circulation on the platform. Grok/X not only condones this activity, which by the way is against the law, nor merely facilitates it, but actively encourages it.

If you don’t leave a social media platform when you find out that it endorses and encourages abusive exploitation of children then you are supporting that behaviour and helping to promote it. There is no grey area here in this. If you don’t draw the line here, when will you draw it? Staying on X is morally indefensible. It is the Epstein Island of social media.

Moreover, any institution or organisation that maintains a presence on X must be content to endorse the promotion of child abuse. I would like to hear an explanation from my employer why they think it’s appropriate for them to operate an official account on the Twitter/X that built a machine for generating images of child pornography. Perhaps readers could ask their employers the same question?

My preferred resolution of this matter would be to ban X entirely.

1 Comment »

Maynooth University Library Cat Update

Posted in Maynooth with tags on January 6, 2026 by telescoper

Maynooth University Library Cat has endured the very cold weather we have had recently, but when I met him this lunchtime he was rather hungry. So much so that he scratched my hand in his eagerness to get at the food I put out for him…

P.S. There seems to be a bit of a thaw today.

Leave a comment »

A Frosty Return

Posted in Maynooth with tags , , on January 5, 2026 by telescoper

So here I am, back on campus at Maynooth University, for the first time in 2026. I took a longer route than usual to my office this morning as I thought the South Campus would look pretty with all the frost around, as indeed it was:

The temperature was well below freezing last night. Today was refuse collection day and I happened to see the crew empty my bins first thing. They struggled to do so as the lids were frozen down. I think there might be a bit of a thaw during the day, but the forecast is that the temperature will barely make it above zero and there’ll be more frost tonight. No snow is forecast for Maynooth.

I topped up the bird feeders in my garden before I left for work. On Saturday I bought a new feeder designed for smaller and nimbler birds; since then there have been several blue tits and various finches using it. I’ve got nothing against the larger birds, but they do tend to hog the other feeders. I suppose it won’t be long until crows try to wreck the new one, but for the time being it’s intact.

Anyway, I have to prepare a revision lecture for this afternoon so ahead of that I need to do a bit of revision myself…

1 Comment »

Den Bortkomne Sauen

Posted in Music with tags , , , , on January 4, 2026 by telescoper

The weather has been much colder for the past few days, which is probably why this piece of music popped into my head and I thought I’d share it here. It’s a Norwegian folk song called Den Bortkomne Sauen (“The Lost Sheep”) and it’s played by Annbjørg Lien on Hardanger fiddle and Iver Kleive on pipe organ. In case you weren’t away the Hardanger fiddle is similar to a normal violin, which has four strings, but underneath them there are four or five others to produce sympathetic vibrations when the main strings are bowed. This makes for a very unique sound, and adds to the haunting atmosphere evoked by this piece.

The theme music for one of my all-time favourite movies, Fargo, released 30 years ago in 1996, was based on this tune which was originally written by the person who wrote all the best tunes, Trad…

P.S. I like this track so much I bought the whole album, Felefeber, which is wonderful!

4 Comments »

Not a Weekly Update from the Open Journal of Astrophysics – 03/01/2026

Posted in Maynooth, Open Access with tags , , , , on January 3, 2026 by telescoper

Not entirely surprisingly, we have not published any papers at the Open Journal of Astrophysics since the last update on 27th December 2025. Of course many authors have been on holiday and there were no arXiv announcements on either Tuesday 30th December or Thursday 1st January anyway. Although we had a few papers accepted before the break, none of them appeared this past week. I dare say some of them will appear next week. We will be starting Volume 9 in 2026, as soon as there is a paper to publish in it.

There being no papers to report, instead of doing one of the regular Saturday updates, I’d like to take the opportunity afforded by this pause to thank everyone who has supported the Open Journal of Astrophysics this year – Editors, Reviewers, Authors and the excellent Library staff at Maynooth University Library – and who have made it such a bumper year. I’d also like to repeat a call for volunteers to join the Editorial Board. In 2023 we published just 50 papers, and in 2025 the figure was 213, so we have more than quadrupled in two years. How many will we publish in 2026?

Here is a graphic showing the number of new papers submitted to the Open Journal of Astrophysics since January 2020:

As the legend explains, this is only the first submission of a paper – resubmissions of revised papers are not included. You can see the thicket is getting denser all the time!

The increasing number of articles is of course very welcome indeed, but it is increasing the load on our Editorial Board many of whom are also very busy with other things. We have expanded the Board recently, but we’re always for volunteers to join the team, in any area of astrophysics. As a reminder, here are the areas we cover, corresponding to the sections of astro-ph on the arXiv:

  • astro-ph.GA – Astrophysics of Galaxies. Phenomena pertaining to galaxies or the Milky Way. Star clusters, HII regions and planetary nebulae, the interstellar medium, atomic and molecular clouds, dust. Stellar populations. Galactic structure, formation, dynamics. Galactic nuclei, bulges, disks, halo. Active Galactic Nuclei, supermassive black holes, quasars. Gravitational lens systems. The Milky Way and its contents
  • astro-ph.CO – Cosmology and Nongalactic Astrophysics. Phenomenology of early universe, cosmic microwave background, cosmological parameters, primordial element abundances, extragalactic distance scale, large-scale structure of the universe. Groups, superclusters, voids, intergalactic medium. Particle astrophysics: dark energy, dark matter, baryogenesis, leptogenesis, inflationary models, reheating, monopoles, WIMPs, cosmic strings, primordial black holes, cosmological gravitational radiation
  • astro-ph.EP – Earth and Planetary Astrophysics. Interplanetary medium, planetary physics, planetary astrobiology, extrasolar planets, comets, asteroids, meteorites. Structure and formation of the solar system
  • astro-ph.HE – High Energy Astrophysical Phenomena. Cosmic ray production, acceleration, propagation, detection. Gamma ray astronomy and bursts, X-rays, charged particles, supernovae and other explosive phenomena, stellar remnants and accretion systems, jets, microquasars, neutron stars, pulsars, black holes
  • astro-ph.IM – Instrumentation and Methods for Astrophysics. Detector and telescope design, experiment proposals. Laboratory Astrophysics. Methods for data analysis, statistical methods. Software, database design
  • astro-ph.SR – Solar and Stellar Astrophysics. White dwarfs, brown dwarfs, cataclysmic variables. Star formation and protostellar systems, stellar astrobiology, binary and multiple systems of stars, stellar evolution and structure, coronas. Central stars of planetary nebulae. Helioseismology, solar neutrinos, production and detection of gravitational radiation from stellar systems.

We are looking for experienced scientists in any of these areas, and it would indeed be useful to have people who can cover a range of subjects (as some of our existing editors do). Since we don’t charge authors or readers we can not offer payment to Editors but it is nevertheless a way of providing a service to the community. If you’re interested, please get in touch either through the Open Journal website here, through a message on Mastodon here or BlueSky here.

2 Comments »

Sunrise, Sunset, Solstice and Perihelion

Posted in The Universe and Stuff with tags , , , , on January 2, 2026 by telescoper

I was on the train earlier today when I remembered that we are getting close to the time when Earth reaches its perihelion, i.e. the point in its orbit when it is closest to the Sun. This occurs at 17.15 GMT tomorrow (Saturday 3rd January 2026), in fact. At this time the distance from the Sun’s centre to Earth’s centre will be 147,099,894 km  This year, aphelion (the furthest distance from the Sun) is at 18.30 GMT on July 6th 2026 at which point the centre of the Earth will be 152,087,774 km from the centre of the Sun. You can find a list of times and dates of perihelion and aphelion for future years here.

Earth’s elliptical orbit viewed at an angle (which makes it look more eccentric than it is – in reality is very nearly circular).

At perihelion the speed of the Earth in its orbit around the Sun is greater than at aphelion (about 30.287 km/s versus 29.291 km/s). This difference, caused by the Earth’s orbital eccentricity, contributes to the difference between mean time and solar time which, among other things, influences the time of sunrise and sunset at the winter solstice that happened a couple of weeks or so ago.

Incidentally, although the Solstice took place on 21st December, it was not until the end of 2025 that we experienced the latest sunrise. The longest day means neither the latest sunrise nor the earliest sunset. The earliest sunset was actually on December 15th in Dublin.

It surprises me how many people think that the existence of the seasons has something to do with the variation of the Earth’s distance from the Sun, thinking that the closer to the Sun we get the warmer the weather will be. The fact that perihelion occurs in the depth of winter should convince anyone living in the Northern hemisphere that this just can’t be the case, as should the fact that it’s summer in the Southern hemisphere while it is winter in the North.

The real reason for the existence of seasons is the tilt of the Earth’s axis of rotation. I used to do a little demonstration with a torch – flashlight to American readers- to illustrate this when I taught first-year astrophysics. If you shine a torch horizontally at a piece of card it will illuminate a patch of the card. Keep the torch at the same distance but tilt the card and you will see the illuminated patch increase in size. The torch is radiating the same amount of energy but in the second case that energy is spread over a larger area than in the first. This means that the energy per unit area incident on the card is decreases when the card is tilted. It is that which is responsible for winter being colder than summer. In the summer the Sun is higher in the sky (on average) than in winter. From this argument you can infer that the winter solstice not the perihelion, is the relevant astronomical indicator of winter.

That is not to say that the shape of the Earth’s orbit has no effect on terrestrial temperatures. It may, for example, contribute to the summer in the Southern hemisphere being hotter than in the North, although it is not the only effect. The Earth’s surface possesses a significant North-South asymmetry: there is a much larger fraction of ocean in the Southern hemisphere, for example, which could be responsible for moderating any differences in temperature due to insolation. The climate is a non-linear system that involves circulating air and ocean currents that respond in complicated ways and on different timescales not just to insolation but to many other parameters, including atmospheric composition (especially the amount of water vapour).

The dates when Earth reaches the extreme points on its orbit (the apsides) are not fixed because of the variations in its orbital eccentricity so, in the short-term, the dates can vary up to 2 days from one year to another. The perihelion distance varies slightly from year to year too; it will be slightly larger next year than this year, for example. There is however a long-term trend for perihelion to occur later in the year. For example, in 1246, the December Solstice (Winter Solstice for the Northern Hemisphere) was on the same day as the Earth’s perihelion. Since then, the perihelion and aphelion dates have drifted by an average of one day every 58 years. This trend will continue, meaning that by the year 6430 the timing of the perihelion and the March Equinox will coincide, although I hope to have retired by then…

3 Comments »

« Older Entries
Newer Entries »