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New Publication at the Open Journal of Astrophysics

Posted in OJAp Papers, Open Access, The Universe and Stuff with tags , , , , , , , on July 5, 2022 by telescoper

Time to announce another new publication in the Open Journal of Astrophysics! This one, published on Sunday, is the 8th paper in Volume 5 (2022) and the 56th in all.

The latest publication is entitled “Search for a distance-dependent Baryonic Tully-Fisher Relation at low redshifts” and is written by by Aditi Krishak (IISER-Bhopal, India) and Shantanu Desai (IIT Hyderabad, India).

This paper is in the Cosmology and Nongalactic Astrophysics folder.

Here is a screen grab of the overlay which includes the abstract:

 

 

You can click on the image to make it larger should you wish to do so. You can find the arXiv version of the paper here.

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R.I.P. Jim Bardeen (1939-2022)

Posted in Biographical, The Universe and Stuff with tags , , , , , on July 4, 2022 by telescoper

I was saddened this morning to hear news of the death at the age of 83 of Jim Bardeen who passed away on June 20th 2022. Jim – the son of John Bardeen, who won two Nobel physics prizes – did important work in theoretical cosmology and general relativity. In my own field of cosmology he is probably best known for his work on perturbation theory where he clarified many longstanding issues about gauge-dependence and as the first author of the famous and heavily cited “BBKS” (Bardeen, Bond, Kaiser & Szalay) paper, published in 1986:

BBKS

I received this as a very hefty preprint when I started my graduate studies back in 1985 and it scared the hell out of me. I still have the photocopy of the published version I made when it came out (in the days when PhD meant Doctor of Photocopying). You can find the paper on the NASA/ADS system here.

I met Jim Bardeen only once, at an Aspen Summer Workshop back in the 90s. He was a very shy and modest man but very kindly and polite. I remember a couple of times out hiking with him, when a discussion about physics was going on he would keep quiet until he had figured out what he thought and when he did choose to speak it was usually brief and invariably very incisive. He didn’t write all that many papers either, but those he did publish were invariably excellent.

Rest in peace, James Maxwell Bardeen (1939-2022)

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On Astropy

Posted in The Universe and Stuff with tags , , on July 3, 2022 by telescoper

Just a quick post to draw your attention to an important paper on arXiv about the Astropy Project, which is community effort to develop a common core package for Astronomy in Python and foster an ecosystem of interoperable astronomy packages. The abstract of the paper is:

The Astropy Project supports and fosters the development of open-source and openly-developed Python packages that provide commonly needed functionality to the astronomical community. A key element of the Astropy Project is the core package astropy, which serves as the foundation for more specialized projects and packages. In this article, we summarize key features in the core package as of the recent major release, version 5.0, and provide major updates for the Project. We then discuss supporting a broader ecosystem of interoperable packages, including connections with several astronomical observatories and missions. We also revisit the future outlook of the Astropy Project and the current status of Learn Astropy. We conclude by raising and discussing the current and future challenges facing the Project.

One of the great advantages of using Python for scientific programming in general and for applications to astrophysics in particular is the existence of extensive software libraries of which Astropy is a prominent example. This is one reason why Python is now the state-of-the-art language in many fields, as exemplified by the following graphic (Figure 1 from the paper) showing the frequency of mentions of various languages in the astronomical literature.

This is on a logarithmic scale so Python is really way out in front.

Most people I know use Python for their scientific programming, and most undergraduate physics courses also use it (including mine at Maynooth). I’m a big fan of the astropy project but it faces many challenges, including funding and management issues. I can’t do much about those but I can encourage users of astropy at least to ensure they acknowledge and cite it properly in their papers, following the instructions here.

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Final Reminder – Professorial Position in Observational Astrophysics or Cosmology at Maynooth!

Posted in Maynooth, The Universe and Stuff with tags , , , , on July 1, 2022 by telescoper

With just a few days to go to the deadline (3rd July), I thought I would take the opportunity to remind readers that Maynooth University has a Chair (i.e. Full Professor) position in Astrophysics or Cosmology under the Strategic Academic Leadership Initiative (SALI). I blogged about this scheme here and announced this Chair position originally here.

You can find the full announcement of the competition for all the SALI positions here; you can apply for the position at Maynooth here. The position is now also advertised on the AAS Jobs Register here.

As I said, the deadline for applications is 3rd July 2022, and the provisional start date is January 2023 (although this is flexible). As well as a good salary (starting at €124,683 at current rates, rising by annual increments to €157,611) the position comes with membership of the Irish public service pension scheme, a defined benefit scheme (comparable to the older version of the UK’s USS which has now been scrapped).

The key rationale for these SALI positions is clear from the statement from Simon Harris, the Minister responsible for Third Level education in Ireland:

“Championing equality and diversity is one of the key goals of my department. The Senior Academic Leadership Initiative (SALI) is an important initiative aimed at advancing gender equality and the representation of women at the highest levels in our higher education institutions.

We have a particular problem with gender balance among the staff in Physics in Maynooth, especially in Theoretical Physics where all the permanent staff are male, and the lack of role models has a clear effect on our ability to encourage more female students to study with us.

The wider strategic case for this Chair revolves around broader developments in the area of astrophysics and cosmology at Maynooth. Currently there are two groups active in research in these areas, one in the Department of Experimental Physics (which is largely focussed on astronomical instrumentation) and the other, in the Department of Theoretical Physics, which is theoretical and computational. We want to promote closer collaboration between these research strands. The idea with the new position is that the holder will nucleate and lead a new research programme in the area between these existing groups as well as getting involved in outreach and public engagement.

It is intended that the position to appeal not only to people undertaking observational programmes using ground-based facilities (e.g. those provided by ESO, which Ireland recently joined), or those exploiting data from space-based experiments, as well as people working on multi-messenger astrophysics, gravitational waves, and so on.

Exciting as this position is in itself, it is part of wider developments and we are expecting to advertise further job opportunities in physics and astronomy very soon! I’d be happy to be contacted by any eligible person wishing to discuss this position (or indeed the general situation in Maynooth) on an informal basis.

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A First Course in General Relativity

Posted in Biographical, Cardiff, Maynooth, The Universe and Stuff with tags , on June 30, 2022 by telescoper

This morning I received delivery of a brand new copy of the Third Edition (left) of A First Course in General Relativity by Bernard Schutz. I bought the First edition (right) way back in 1985 when I started out as a graduate student. Not surprisingly there is a lot of additional material in the 3rd edition about gravitational waves, which had not been discovered when the first edition was published. I notice also that Bernard has lost his “F”…

 In fact I have known Bernard for quite a long time, most recently as colleagues in the Data Innovation Research Institute in Cardiff. Before that he chaired the Panel that awarded me an SERC Advanced Fellowship in the days before STFC, and even before PPARC, way back in 1993. It just goes to show that even the most eminent scientists do occasionally make mistakes…

Anyway, the arrival of this book is a double coincidence because I’ve been thinking over the last couple of days about starting to organize teaching for next academic year. This isn’t easy as we still don’t know who is going to be available. We’re interviewing tomorrow for one of our vacant positions, actually. Yesterday also the University Bookshop sent out a request for textbooks to stock ahead of next academic year.

I was reflecting on the fact that I’ve been doing research in cosmology and theoretical astrophysics since 1985 and teaching undergraduate and postgraduate students since 1990 but I’ve never taught a course on general relativity. This may or may not change next year when teaching is allocated. There are many textbooks out there but, prompted by the arrival of Bernard’s new book, I was wondering if anyone reading this blog has any other recommendations, suitable for final-year undergraduate theoretical physics students, that might complement it on the reading list for my first course in general relativity, should I happen to give one?

Suggestions, please, through the comments box below!

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On the Relativity of Time

Posted in The Universe and Stuff on June 25, 2022 by telescoper

I feel seen…

(HT to Stephen Curry for implicating me in this..)

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Schrödinger’s Theatre

Posted in Education, History, The Universe and Stuff with tags , , on June 21, 2022 by telescoper

Although it’s relatively old news in Ireland, a colleague recently sent me a story from Physics World about Trinity College Dublin’s decision to change the name of its Schrödinger Lecture Theatre (to the Physics Lecture Theatre). The Provost, Fellows, Foundation Scholars and the other members of Board, of the College of the Holy and Undivided Trinity of Queen Elizabeth near Dublin (to give it its proper title) took this decision in the light of revelations about Erwin Schrödinger‘s predatory sexual conduct towards very young girls.

According to my careful research carried out by reading his Wikipedia page, Schrödinger never actually worked at Trinity College Dublin; the Theatre in question was named in his honour after he delivered his famous lectures on What is Life there in 1943.

Reactions to the decision to rename the Theatre have generated a wide range of reactions from physicists and non-physicists alike. For my part I think it is the right decision. As the Physics World article states:

As an educational institute, we cannot condone or glorify someone who abused the trust between teacher and student.

Jonathan Coleman, Head of School Physics TCD

To me this is quite different from attaching Schrödinger’s name to his equation or even his cat. His unsavoury conduct should not mean that his scientific achievements should be “cancelled” . These are and should continue to be recognized through terms like Schrödinger’s Equation. As far as I am aware, however, Schrödinger did not build any lecture theatres.

It’s up to Trinity to decide what to call its rooms, of course, but that doesn’t mean we’re not allowed to have opinions about the decision. I’d therefore invite you to express yours through the following poll:

Of course if you wish to expand on your opinion you may do so through the box below.

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Summer Solstice 2022

Posted in History, The Universe and Stuff on June 21, 2022 by telescoper

The Summer Solstice in the Northern hemisphere takes place today, Tuesday 21st June 2022, at 10.14am Irish Time (9.14 UTC). Among other things, this means that tomorrow is the longest day of the year around these parts. According to this website, the interval between sunrise and sunset in Dublin today will be 17 hours 5 minutes and 6 seconds. which is 2 seconds longer than yesterday while tomorrow will be four whole seconds shorter than that.

It’s all downhill from now on.

Days will get shorter from tomorrow until the Winter Solstice in December, although this does not mean that sunset will necessarily happen earlier on 22nd than it does tomorrow. In fact it is a little later. Nor does it mean that sunrise will happen later tomorrow; in fact it is a little earlier.

You can find such things out by looking at a table of the local mean times of sunrise and sunset for Dublin around the 2022 summer solstice. This shows that the earliest sunrise was actually on 17th June and the latest sunset is on 25th.

This arises because there is a difference between mean solar time (measured by clocks) and apparent solar time (defined by the position of the Sun in the sky), so that a solar day does not always last exactly 24 hours. A description of apparent and mean time was given by Nevil Maskelyne in the Nautical Almanac for 1767:

Apparent Time is that deduced immediately from the Sun, whether from the Observation of his passing the Meridian, or from his observed Rising or Setting. This Time is different from that shewn by Clocks and Watches well regulated at Land, which is called equated or mean Time.

The discrepancy between mean time and apparent time arises because of the Earth’s axial tilt and the fact that it travels around the Sun in an elliptical orbit in which its orbital speed varies with time of year (being faster at perihelion than at aphelion).

If you plot the position of the Sun in the sky at a fixed time each day from a fixed location on the Earth you get a thing called an analemma, which is a sort of figure-of-eight curve whose shape depends on the observer’s latitude. Here’s a photographic version taken in Edmonton, with photographs of the Sun’s position taken from the same position at the same time on different days over the course of a year:

maxresdefault

The summer solstice is the uppermost point on this curve and the winter solstice is at the bottom. The north–south component of the analemma is the Sun’s declination, and the east–west component is the so-called equation of time which quantifies the difference between mean solar time and apparent solar time. This curve can be used to calculate the earliest and/or latest sunrise and/or sunset.

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Euclid Launch Delay

Posted in Euclid, Science Politics, The Universe and Stuff with tags , , on June 17, 2022 by telescoper

Until relatively recently we al thought the European Space Agency’s  Euclid mission would take place later this year (2022). For various reasons that date subsequently slipped to the first quarter of 2023.

Then Russia invaded Ukraine which, because Euclid was intended to be launched on a Russian Soyuz vehicle a further delay seemed likely (see here). The subsequent decision by the Russians to remove all their personnel from the launch site at Kourou (see here) made these even more likely as an alternative launch vehicle would have to be used.

There was an update about the situation at the recent Euclid Consortium meeting in Oslo which I could not attend but which I referred to here. The basic problem is that Plan B involves launching Euclid on an Ariane 6 rocket (which comes in two varieties, Ariane62 and Ariane64, with two and four boosters respectively). The problems are (a) that Ariane 6 is that it hasn’t yet had its first flight and (b) Euclid isn’t the only spacecraft now having to find an alternative launcher. The competition from commercial and military satellites may mean a lengthy delay to the Euclid Launch unless lobbying succeeds at a political level.

It has now emerged that earliest feasible date for launch on an Ariane 6 rocket is the 3rd quarter of 2024 and it may well be later than that, the uncertainty exacerbating the effects of the delay itself.

This is all very unfortunate. Euclid is now fully built and ready so a lengthy delay would be very damaging to morale. More concretely, many researchers employed to work on Euclid are on fixed-term contracts which will now expire before they can complete their work. This will have a very serious effect on younger researchers. To keep everything going while the spacecraft waits for a launch will be extremely expensive: the Euclid Consortium Board estimates a cost of about €50M for every year of delay and it is by no means clear where those funds would come from.

It seems to me that the best hope for a resolution of this problem would be for ESA to permit the launch of Euclid using something other than Ariane 6, which means using a vehicle supplied by an independent commercial operator. I sincerely hope ESA is able to come up with an imaginative solution to this very serious problem.

P.S. With this update, the odds on me retiring before Euclid is launched have just shortened considerably…

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Gaia’s Third Data Release!

Posted in The Universe and Stuff with tags , , on June 13, 2022 by telescoper

It seems like only yesterday that I blogged about the second release of data from the European Space Agency’s Gaia mission but today sees the release of the third data set, known to its friends as DR3. This completes the set after some initial data were released early as EDR3 back in 2020.

Gaia on the Launchpad at Kourou, French Guyana, on 13th December 2013

In case you weren’t aware, Gaia, launched way back in 2013, is an ambitious space mission to chart a three-dimensional map of our Galaxy, the Milky Way, in the process revealing the composition, formation and evolution of the Galaxy. Gaia will provide unprecedented positional and radial velocity measurements with the accuracy needed to produce a stereoscopic and kinematic census of about one billion stars in our Galaxy and throughout the Local Group. This amounts to about 1 per cent of the Galactic stellar population.

Gaia is likely to operate until round about November 2024, so there’s a lot of data yet to come.

You can find a complete list of what is in DR3 here and if you want to go straight into the papers based on this dataset, go here. There is a nice promotional video here:

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