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Firearms Units

Posted in The Universe and Stuff on June 2, 2025 by telescoper

Disturbed by the news of a shooting incident in Carlow yesterday that resulted a man’s death, I thought I’d check what the rules are for owning firearms in Ireland. I found a summary here. This is the introduction:

Spot the deliberate mistake!

I don’t possess an airgun, but I understand the pellets they fire range have a mass of at least 0.675 grammes. If, as seems likely, it is the kinetic energy of the pellet that is limited to 1 joule, then what is the maximum allowed muzzle velocity for an unlicensed airgun? Give your answer in metres per second.

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The Shaw Prize for Astronomy 2025

Posted in The Universe and Stuff with tags , , , , on June 1, 2025 by telescoper
Dick Bond (left) and George Efstathiou (right)

I’m a few days late on this, as the announcement on 27th May came at a very busy time, but it’s a pleasure to pass on the news that the 2025 Shaw Prize for Astronomy has been awarded to Dick Bond and George Efstathiou. Congratulations to both on a very well deserved award!

The full citation can be found here, but the first paragraph reads:

The Shaw Prize in Astronomy 2025 is awarded in equal shares to John Richard Bond, Professor of the Canadian Institute for Theoretical Astrophysics and University Professor at the University of Toronto, Canada and George Efstathiou, Professor of Astrophysics at the University of Cambridge, UK for their pioneering research in cosmology, in particular for their studies of fluctuations in the cosmic microwave background. Their predictions have been verified by an armada of ground-, balloon- and space-based instruments, leading to precise determinations of the age, geometry, and mass-energy content of the universe.

One of the first papers I was given to read when I started my postgraduate studies in 1985 was the pioneering Bond & Efstathiou (1984) “Cosmic background radiation anisotropies in universes dominated by nonbaryonic dark matter”. Here is the abstract:

This work was hugely influential and prescient in many ways. It does remind me, though, that in the 1980s, before the detection of large-scale anisotropies by the Cosmic Background Explorer (COBE) announced in 1992, the prevailing mentality was to find models in which the predicted cosmic microwave background anistropies were as small as possible. The COBE fluctuations turned out to be rather larger than those predicted in the model discussed in the paper, which was one reason why the standard cosmological model now has a lower density of dark matter than then.

On a more technical level, the paper also reminds us that it was to be a while until the angular power spectrum, as opposed to the correlation function, became the standard tool it is now for quantifying the statistical properties of these temperature fluctuations.

The Shaw Prize wasn’t awarded for just this paper, of course, but I think it’s emblematic of the sustained importance and influence of the work of the Laureates over many years.

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Weekly Update from the Open Journal of Astrophysics – 31/05/2025

Posted in OJAp Papers, Open Access, The Universe and Stuff with tags , , , , , , , , , , , , , , , on May 31, 2025 by telescoper

Once again it’s time for the weekly Saturday morning update of papers published at the Open Journal of Astrophysics. Since the last update we have published five new papers, which brings the number in Volume 8 (2025) up to 67; the total so far published by OJAp has passed the 300 mark and is now up to 302. If we keep up at the same rate for the rest of the year as we did for the first five months now completed, we will publish around 160 papers altogether in 2025.

In chronological order of publication, the five papers published this week, with their overlays, are as follows. You can click on the images of the overlays to make them larger should you wish to do so.

The first paper to report is “Which is the most eccentric binary known? Insights from the 2023/4 pericenter passages of Zeta Boötis and Eta Ophiuchi” by Idel Waisberg, Ygal Klein and Boaz Katz (Weizmann Institute of Science, Israel).  This is a report of interferometric observations of two very eccentric binary star systems, published on Tuesday 27th May 2025 in the folder Solar and Stellar Astrophysics. The overlay is here:

You can read the final accepted version on arXiv here.

The second paper to report is “On the full non-Gaussian Surprise statistic and the cosmological concordance between DESI, SDSS and Pantheon+” by Pedro Riba Mello & Miguel Quartin (Universidade Federal do Rio de Janeiro, Brazil), and Bjoern Malte Schaefer & Benedikt Schosser (Heidelberg, Germany). This paper is in the folder Cosmology and NonGalactic Astrophysics and was published on Tuesday 27th May 2025. The paper presents an application of the “Surprise Statistic”, based on the Kullback-Leibler divergence, as a measure of the difference between results inferred from different data sets.

The overlay is here:

 

You can find the officially-accepted version of the paper on arXiv here.

The third paper we published last week, and our 300th overall, is “Cosmic Ray Feedback in Massive Halos: Implications for the Distribution of Baryons” by Eliot Quataert (Princeton, USA) and Philip F. Hopkins (Caltech, USA).  This was published on Thursday 29th May in the folder Cosmology and NonGalactic Astrophysics. The paper discusses the effects of cosmic rays produced by massive black holes on the structure of the baryonic component of galaxies and how these might affect cosmological parameter estimation. The overlay is here:

 

You can read the officially accepted version of this paper on arXiv here.

The next one to report is “Mixing neutron star material into the jets in the common envelope jets supernova r-process scenario” by Noam Soker (Technion, Israel). This was published on Thursday 27th May in the folder High-Energy Astrophysical Phenomena; it presents a discussion of the chemical enrichment of an evolved star consequent upon its ingestion of a neutron star.

The overlay is here:

You can find the officially accepted version on arXiv here.

Last, but by no means least, for this week we have “Dark Energy Survey Year 6 Results: Synthetic-source Injection Across the Full Survey Using Balrog” by Dhayaa Anbajagane (Kavli Institute, Chicago) et al. (81 authors) on behalf of the Dark Energy Survey Collaboration. It was also  published on Thursday 27th May  2025, but in the folder Cosmology and NonGalactic Astrophysics. It is about testing the Dark Energy Survey analysis pipeline using synthetic sources.

The overlay is here:

 

You can find the officially accepted version on arXiv here.

That’s all the papers for this week. I’ll post another update next weekend.

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The 300th Publication at the Open Journal of Astrophysics

Posted in OJAp Papers, Open Access, The Universe and Stuff with tags , , on May 29, 2025 by telescoper

It was on October 8th last year that we published the 200th paper at the Open Journal of Astrophysics. Today, on 29th May 2025, less than 8 months later, we have reached the 300 mark with this paper:

The authors are Eliot Quataert (Princeton, USA) and Philip F. Hopkins (Caltech, USA). We continue to have a large number of papers from authors based in the USA.

I published another two papers this morning and will include all the papers published this week (Including the 300th) in the usual weekly update on Saturday. Based on the 67 papers published so far this year and the activity in the OJAp worklow, I estimate we will publish at least 150 papers this year, which means we should reach the the 400 mark early next year.

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Congratulations, Dr Gallagher!

Posted in Biographical, Maynooth, The Universe and Stuff with tags , , , on May 26, 2025 by telescoper

This week is off to a good start! This morning my postgraduate research student Aoibhinn Gallagher passed a viva voce examination on her thesis Cosmological Structure Formation Using Wave Mechanics. There will be a few formalities to deal with, some minor corrections to make, various forms to fill in, and the result has to be approved by the examination board, and so on, but basically that’s a job well done. Congratulations, Dr Gallagher!

Left to Right: Dr John Regan (internal examiner), Aoibhinn Gallagher (PhD candidate), and Prof. Cora Uhlemann (external examiner).

P.S. You can get an idea of some of the content of Aoibhinn’s thesis here.

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Weekly Update from the Open Journal of Astrophysics – 24/05/205

Posted in OJAp Papers, Open Access, The Universe and Stuff with tags , , , , , , , , , , , , , , , , , on May 24, 2025 by telescoper

It’s  time once again for the regular Saturday update of papers published during the past week at the Open Journal of Astrophysics. Since the last update we have published three new papers, which brings the number in Volume 8 (2025) up to 62 and the total so far published by OJAp up to 297.

In chronological order of publication, the three papers published this week, with their overlays, are as follows. You can click on the images of the overlays to make them larger should you wish to do so.

The first paper to report is: “Jet-shaped filamentary ejecta in common envelope evolution” by Ron Schreier, Shlomi Hillel and Noam Soker (Technion, Haifa, Israel). This paper, which was published on Monday May 19th 2025 in the folder High-Energy Astrophysical Processes, presents three-dimensional hydrodynamical simulations of common envelope evolution of a neutron star inside the envelope of a rotating red supergiant with Rayleigh-Taylor instabilities forming filamentary ejecta.

The overlay is here:

You can find the officially accepted version on arXiv here.

Second one up is “Weighing The Options: The Unseen Companion in LAMOST J2354 is Likely a Massive White Dwarf” by M. A. Tucker, A. J. Wheeler & D. M. Rowan (Ohio State University, USA) and M. E. Huber (U. Hawaii, USA). This paper was published on Tuesday 20th May 2025 in the folder for Solar and Stellar Astrophysics. It discusses a spectroscopic study of the binary system LAMOST J235456.73+335625 (J2354) with a discussion of the implications for the nature of the dark component.

The overlay is here:

 

You can find the officially-accepted version of the paper on arXiv here.

The third and last paper of the week, published on Thursday May 22nd 2025, also in the folder Solar and Stellar Astrophysics, is “How to use Gaia parallaxes for stars with poor astrometric fits” by Kareem El-Badry (Caltech, USA).  This paper presents a method for extracting reasonable estimates of stellar parallaxes from Gaia data when the overall astrometric solution is unreliable due to errors and noise

Here is the overlay:

You can find the officially accepted version of this paper on arXiv here.

That’s all the papers for this week. Looking at the publishing workflow, I expect we will pass the 300 mark next week. We’ll see when I post the next update next Saturday.

 

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Getting there…

Posted in Biographical, Maynooth, The Universe and Stuff with tags , , on May 23, 2025 by telescoper

Despite having to take time out today to attend an Emergency Meeting of IFUT (about matters which may or may not be public soon), my marking duties are about halfway done and roughly on schedule. For one module, I have 60% of the assessment scores for 32 students and, for the other, about 40% of the assessment for 23 students. I make that about 51.6 of the total. The last piece of the puzzle won’t arrive on my desk until Wednesday morning, by which time I hope to have completed 100% of the 32, leaving just 60% of the 23, amounting to about 16.7% of the total, to be done in the second half of next week. I hope this clarifies the situation.

Meanwhile the weather has taken a turn for the worse, no doubt because of the imminent Bank Holiday weekend in the UK. Monday 26th is a holiday there. In Ireland, the next holiday is on Monday June 2nd, Lá Saoire i mí an Mheithimh See if you can pronounce that! Next Friday (30th May) is the day of the season finale of the National Symphony Orchestra at the National Concert Hall, which is Mahler’s 9th Symphony. I hope I’ll be finished marking in time for that so I can relax over the holiday weekend after what will have been a very hectic week and take some time off the following week to do a bit of travelling to attend to some personal matters.

Next week will start off, however, with the PhD viva of one of my students. I won’t be attending the actual examination, of course, but will be there for the subsequent formalities. It’s a distraction from grading, but a nice one.

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R.I.P. Jayant Narlikar (1938-2025)

Posted in Biographical, R.I.P., The Universe and Stuff with tags , , , , , , on May 20, 2025 by telescoper
Professor Jayant Vishnu Narlikar (1938-2025)

I heard this morning of the death at the age of 86 of renowned Indian cosmologist Jayant Vishnu Narlikar. I understand he died peacefully in his sleep in Pune after a brief illness.

Scientifically, Jayant Narlikar is probably best known for his work with Fred Hoyle on a conformal gravity theory and as an advocate of the Steady State theory of cosmology. In India however his fame extended far beyond the world of research, as an educator and science popularist, as well as Founder-Director of the Inter-University Centre for Astronomy and Astrophysics (IUCAA) in Pune. Those who met him – as I was lucky enough to do – will also remember him as a kind and gracious man, and a self-effacing inspirer of young scientists. During my visit I gave a talk there, which Narlikar attended, and we had a very nice conversation afterwards from which I learnt a huge amount.

The Directorship at IUCAA came with a house which had a very nice lawn, on which I remember playing croquet with Donald Lynden-Bell and others, but that’s another story. Another random thing I remember is that I remember is that Narlikar’s username on the IUCAA email system was “jvn” and he was often referred to informally by that name.

Although he never really abandoned the Steady State cosmology, despite the weight of evidence in favour if the Big Bang, it is to Narlikar’s great credit that he didn’t try to impose his own scientific ideas on those working at IUCAA. In fact he assembled an excellent group of cosmologists and astrophysicists and encourage them to do whatever they liked.

I first visited IUCAA in 1994 to work with Varun Sahni. In those days Westerners mainly went to Pune to visit an ashram (usually the one run by the guru Rajneesh). I remember when I arrived on the train from Mumbai and tried to get a taxi to the IUCAA campus, the driver asked me “which ashram?” I had long hair and a beard at that time, so I looked a potential hippy. I said, “No ashram. Professor Narlikar”. He knew exactly where to take me; “Narlikar” was a household name in India, where the newspapers are awash with tributes today (e.g. here) and where his loss will be keenly felt.

Rest in peace Jayant Narlikar (1938-2025)

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A galaxy at redshift z=14.44?

Posted in OJAp Papers, The Universe and Stuff with tags , , , , , on May 19, 2025 by telescoper

This morning’s arXiv mailing presented me with a distraction from examination marking in the form of a paper by Naidu et al. with this abstract:

This paper has been submitted to the Open Journal of Astrophysics. In the relatively recent past, papers like this about record-breaking galaxies would normally be submitted to Nature so perhaps we’re at last starting to see a change of culture?

I usually feel a bit conflicted in situations when a paper has been submitted for editorial review there. In this case I am posting it here for two reasons: one is that I am not the Editor responsible for this paper; the other is that the arXiv submission specifically says

Submitted to the Open Journal of Astrophysics. Comments greatly appreciated and warmly welcomed!

In order to generate flagging it here to encourage people to comment, either through the box below or by contacting the authors.

For reference, here is the key plot showing the spectrum from which the redshift is determined. It is rather noisy, but the Lyman break seems reasonably convincing and there are some emission lines that appear to offer corroborative evidence:

You might want to read this article (another OJAp paper) which contains this plot showing how galaxies at redshift z>10 challenge the standard model:

Please read the paper and comment if you wish!

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Weekly Update from the Open Journal of Astrophysics – 17/05/2025

Posted in OJAp Papers, Open Access, The Universe and Stuff with tags , , , , , , , , , , , , on May 17, 2025 by telescoper

It’s a lovely Saturday morning in May, and it’s time for the weekly  update of papers published at the Open Journal of Astrophysics. Since the last update we have published four new papers, which brings the number in Volume 8 (2025) up to 59 and the total so far published by OJAp up to 294.

In chronological order of publication, the four papers published this week, with their overlays, are as follows. You can click on the images of the overlays to make them larger should you wish to do so.

The first paper to report is: “Multi-Phase Thermal Structure & The Origin of the Broad-Line Region, Torus, and Corona in Magnetically-Dominated Accretion Disks” by Philip F. Hopkins (Caltech, USA). This was published on Monday May 12th in the folder Astrophysics of Galaxies. It presents simple accretion disk model that predicts the properties of many features including the dusty torus, broad-line region, continuum emission and coronal gas.

The overlay is here:

You can find the officially accepted version on arXiv here.

Second one up is “Sparsity covariance: a source of uncertainty when estimating correlation functions with a discrete sample of observations in the sky” by Pierre Fleury (U. Montpellier, France). This one was published on Tuesday 13th May 2025 in the folder Cosmology and NonGalactic Astrophysics.  This paper presents a discussion of the uncertainty in cosmological observables caused by discrete sampling and a method to compute the covariances resulting from this.

The overlay is here:

You can find the officially-accepted version of the paper on arXiv here.

The third paper of the week, published on Wednesday May 14th 2025,  is “Dark Matter Particle Flux in a Dynamically Self-consistent Milky Way Model” by Lucijana Stanic, Mark Eberlein, Stanislav Linchakovskyy, Christopher Magnoli, Maryna Mesiura, Luca Morf, Prasenjit Saha (University of Zurich, Switzerland) and Eugene Vasiliev (University of Surrey, UK). This one presents a study of the behaviour of dark matter in an anisotropic model for the Milky Way halo with implications for particle detection rates. It is in the folder Astrophysics of Galaxies.

Here is the overlay:

You can find the officially accepted version of this paper on arXiv here.

The last paper published this week is “Too fast to be single: Tidal evolution and photometric identification of stellar and planetary companions” by Ilay Kamai and Hagai B. Perets (Technion, Haifa, Israel). This one was published on Friday 16th May 2025 in the folder Solar and Stellar Astrophysics. It presents an analysis of the rotation of stars observed in the Kepler field to identify non-single systems with high spin rates resulting from tidal effects.

Here is the overlay:

The official published version can be found on the arXiv here.

That’s all the papers for this week. I’ll post another update next week.

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