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!
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.
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).
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…
For last year’s words belong to last year’s language And next year’s words await another voice. And to make an end is to make a beginning.
From Four Quartets, ‘Little Gidding’ by T. S. Eliot.
So it’s New Year’s Day. Athbhliain faoi mhaise dhaoibh!
For me this brings the festive season to an end. I’ve been eating and drinking too much for the last week as one is supposed to. Last night I brought in the new year with a dish of roast duck and the last of the Christmas vegetables. I think I’ll be buying any sprouts and parsnips for a while. When the iron tongue of midnight told twelve, I had a glass of excellent Irish Whiskey in the form of Clonakilty Single Pot Still (46%). It has been a most enjoyable week, but heightened level of self-indulgence has been rather exhausting, and I’ll be taking things a bit easier for a few days before I go back to work on Monday. It’s hard work being a glutton.
Anyway, I thought I’d mention a few things looking forward to the New Year.
January will, as usual, be dominated by examinations, and especially the marking thereof. The first examination for which I am responsible is on January 12th. The examination, incidentally, will be held in the Glenroyal Hotel in Maynooth as the Sports Hall on campus – usually a major exam venue – is out of commission due to building work.
I have a couple of writing deadlines, in addition to having to correct the examinations, so it will be a busy January.
Then February sees the start of a new semester. I’ll be teaching Particle Physics again. I was a bit surprised to be asked to teach this again, as I was filling last year in for our resident particle physicist who was on sabbatical. I’m glad to be able to continue with it given the work I put in to do it last time. My other module is Computational Physics which I have taught at Maynooth every year since 2018, apart from 2024 when I was on sabbatical. This time, however, I will have to think hard about how to deal with the use of generative AI in the coursework.
Will I get to teach any astrophysics or cosmology at Maynooth before I retire? That’s looking very unlikely. I think it’s probable that the new academic year, starting in September, will find me teaching the same modules as last year.
The year ahead will also see the first data release (DR1) from the European Space Agency’s Euclid Mission. The date for that will be October 21st 2026. This is a hard deadline. There’s a huge amount of work going on within the Euclid Consortium to extract as much science as possible from the observations so far before the data becomes public, but you’ll have to wait until October to find out more!
This reminds me that I forgot to share this nice image from Euclid that was released just before Christmas.
Galaxy NGC 646 looking like a cosmic holiday garland in this image from the European Space Agency’s Euclid space telescope.
Once upon a time, WordPress used to send an email about the year’s blog statistics, etc, but it stopped doing that some time ago. I checked this morning, however, and learned that traffice on the blog in 2025 was up by 2.6% since 2024. I’m not sure how meaningful this is, because there is so much scraping going on these days. That figure doesn’t include the people who get posts via email or RSS or via other platforms such as the Fediverse.
While I’m on about social media I’ll mention a stat about my Bluesky account. I joined Bluesky in 2023 when I abandoned Xitter. As of today I have 8,078 BlueSky followers, which is more than I ever had on X, and with far higher levels of engagement and much friendlier interactions.
I’m also on Mastodon, although with a much smaller following (1.4k). This blog also has a separate existence on Mastodon here. I very much like the federated structure of Mastodon (which, incidentally, accords with my view of how academic publishing should be configured) and am a bit disappointed that it doesn’t seem to have caught on as much as it should.
That disappointment pales into insignificance, however, with the outrage I feel that my employer – along with most other universities – persists in using Xitter. Touting for trade in a far-right propaganda channel is no way for a institution of higher education to behave. You can read my views on this matter here.
And finally there’s the Open Journal of Astrophysics. The year ahead will see the 10th anniversary of our first ever publication – on an experimental prototype platform, long before we moved to Scholastica. It will be next Monday before we resume publishing, starting Volume 9. Which author(s) will be the first to get their final versions on arXiv in 2026? Stay tuned to find out!
I don’t know precisely which picture the poet is referring to for January in his calendar, nor which artist, but it it is undoubtedly an example of a Vanitas or Memento Mori, a genre symbolizing the transience of life, the futility of pleasure, and the certainty of death, and thus the vanity of ambition and all worldly desires. The paintings involved still life imagery of items suggessting the transitory nature of life.
A couple of examples are here:
Between them you find all the elements mentioned in the poem: the skull represents death, the flowers impermanence, the coins personal wealth and the other items worldly knowledge and pleasure. There’s an interesting WordPress blog about the symbolism this genre here:
I missed, until now, the news that on Christmas Day, high winds accompanying a violent storm seriously damaged the historic Lick Observatory.
The gales were strong enough to rip one of the shutters from the dome of the 36″ refracting telescope and send it crashing onto the roof of the adjacent building.
The Observatory remains closed to the public while the structural damage is assessed and repairs made. Fortunately it seems nobody was hurt and no instruments were affected.
Here’s a video of the detached shutter being removed
The Lick Observatory is located on Mount Hamilton near San Jose in California. A donation by San Francisco millionaire James Lick enabled the construction of the 36” (diameter) refractor, the most powerful telescope in the world at the time. The Observatory was almost destroyed in 2020 by a wildfire, but the new incident is the most serious damage in its 137-year history.
As I blogged about here, the Lick Observatory played an important role in the development of our understanding of the large-scale structure of the Universe, specifically with the creation of the Lick galaxy survey prepared by Charles Donald Shane and Carl Alvar Wirtanen and published in 1967 (Publ. Lick. Observatory 22, Part 1). In my more poetic moments, the image on the left puts me in mind of W.B. Yeats: Had I the heavens’ embroidered cloths.
That catalogue was still proving a useful resource well into the 1990s; I was part of various analyses of it myself, starting with this paper from 1991. It was eventually superceded by the arrival of large-scale galaxy redshift surveys, but it remaining an amazing achievement.
The Lick Galaxy survey was not performed with the 36″ refractor mentioned above, however, but by twin 20″ Carnegie astrographic telescopes housed in a different dome. As far as I know, these were not damaged in the storm.
The other night I watched the 2023 film Oppenheimer on TV. I had seen it before, on a plane flight, and enjoyed it, though I thought it was overlong. Fortunately it was a long flight. Watching it again a couple of days ago reminded me of something that struck me first time, and that was the cameo performance by Kenneth Branagh as Niels Bohr. You can see him at the start of the trailer here:
Niels Bohr was born in Copenhagen, a place I visited many times in the past and can recognize the local accent, though had never heard the speaking voice of Niels Bohr himself. I was a underwhelmed by Branagh’s rendition because he doesn’t sound very Danish to me. I assumed that because it was a relatively small part, Branagh didn’t put much effort into it. He doesn’t look like Niels Bohr, either.
But what did Niels Bohr actually sound like? Here is a lecture by him given in 1957 so you can decide for yourself.
Having heard this recording I think Kenneth Branagh’s version is not too far off, in fairness, though there are clear vocal mannerisms he did not capture.
The thing that strikes me most about the lecture, however, is that his delivery is very pedestrian, not to say rambling. People say he was like that in ordinary conversation too…
I wasn’t planning to do another update this week but I thought it would be best to complete the publications for 2025 at the Open Journal of Astrophysics, so that I don’t have to do a bigger update in the new year, and I have a bit of time this morning, so here we go.
Since the last update we have published four papers which brings the number in Volume 8 (2025) up to 201. Adding the 12 papers in the Supplement, this brings the final total for the year up to 213, and the total so far published by OJAp up to 448. In 2023 we published just 50 papers, so we have more than quadrupled in two years.
The first paper this week is “Transverse Velocities in Real-Time Cosmology: Position Drift in Relativistic N-Body Simulations” by Alexander Oestreicher (University of Southern Denmark), Chris Clarkson (QMUL, UK), Julian Adamek (Universität Zürich, CH) and Sofie Marie Koksbang (U. Southern Denmark). This study uses a general relativistic N-body simulation code to explore how cosmological structures affect position drift measurements, a new method for studying cosmic structure formation and velocity fields. This was published on Tuesday 23rd December 2025 in the folder Cosmology and Nongalactic Astrophysics.
The overlay is here:
You can find the officially accepted version on arXiv here and this is the announcement on Mastodon (Fediscience):
New Publication at the Open Journal of Astrophysics: "Transverse Velocities in Real-Time Cosmology: Position Drift in Relativistic N-Body Simulations" by Alexander Oestreicher (University of Southern Denmark), Chris Clarkson (QMUL, UK), Julian Adamek (Universität Zürich, CH) and Sofie Marie Koksbang (U. Southern Denmark)
The second paper of the week is “On the statistical convergence of N-body simulations of the Solar System” by Hanno Rein, Garett Brown and Mei Kanda (U. Toronto, Canada). This study presents numerical experiments to determine the minimum timestep for long-term simulations of the Solar System, finding that timesteps up to 32 days yield physical results. It was published on Tuesday December 23rd in the folder Earth and Planetary Astrophysics.
The overlay is here:
You can find the official version of this one on arXiv here. The federated announcement on Mastodon is here:
New Publication at the Open Journal of Astrophysics: "On the statistical convergence of N-body simulations of the Solar System" by Hanno Rein, Garett Brown and Mei Kanda (U. Toronto, Canada)
Next, published on 24th December 2025 in the folder High-Energy Astrophysical Phenomena, we have “The explosion jets of the core-collapse supernova remnant Circinus X-1” by Noam Soker and Muhammad Akashi (Technion, Haifa, Israel). This paper suggests that the rings in the Circinus X-1 supernova remnant resulted from jet-driven explosions, supporting the jittering-jets explosion mechanism theory for core collapse supernovae.
The overlay is here:
The officially accepted paper can be found on arXiv here and the announcement on Mastodon is here
New Publication at the Open Journal of Astrophysics: "The explosion jets of the core-collapse supernova remnant Circinus X-1" by Noam Soker and Muhammad Akashi (Technion, Haifa, Israel)
Finally for 2025 we have “Quantifying the Fermi paradox via passive SETI: a general framework” by Matthew Civiletti (City University of New York, USA). This was published on Wednesday 24th December in the folder Instrumentation and Methods for Astrophysics. The author uses SETI observations and the Drake Equation to calculate the probability of detecting at least one extraterrestrial signal, highlighting the model’s limitations and potential improvements. The overlay is here:
The officially accepted version can be found on arXiv here and the Mastodon announcement here:
New Publication at the Open Journal of Astrophysics: "Quantifying the Fermi paradox via passive SETI: a general framework" by Matthew Civiletti (City University of New York, USA)
And that concludes the updates for 2025. I’ll be back in a week with the first update of 2026, which will include the first paper(s) of Volume 9.
I’d like to thank everyone who has supported the Open Journal of Astrophysics this year – Editors, Reviewers, Authors and the excellent Library staff at Maynooth – and who have made it such a bumper year. In 2023 we published just 50 papers, so we have more than quadrupled in two years. How many will we publish in 2026?
Posted in Uncategorized on December 25, 2025 by telescoper
Here we are then, Christmas Day. I thought I’d do a quick yule blog in between finishing a rather late breakfast and starting the preparations for dinner*.
Let me just wish you all a Merry Christmas, Nollaig Shona, Nadolig Llawen, Fröhliche Weihnachten, Joyeux Noël, Buon Natale, Feliz Navidad, Feliç Nadal, Glædelig Jul, etc…
And in the words of a traditional Irish toast:
Go mbeirimid beo ar an am seo arís!
(“May we live to see this time next year”)
*Roast beef Chateaubriand, with red wine gravy, honey-roast carrots and parsnips, sprouts, and roast potatoes. Preceded by smoked salmon with asparagus and followed by Christmas pudding and, later on, cheese and port.
Update: et voilà
P.S. I couldn’t resist sharing this cartoon from the Christmas issue of Private Eye:
P.P.S. I find it interesting, from a linguistic point of view, how the French “Noel” (or “Noël”) and Irish “Nollaig” evolved from the Latin “Natalis”.
The spelling of “Noël” with a diaeresis over the “e” indicates that the two vowels are pronounced separately rather than as a diphthong. This may be a relic of the missing consonant in “Natalis”.
Perhaps the Welsh “Nadolig” is some sort of Celtic missing link…
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In the Dark 