Archive for the The Universe and Stuff Category

Job Opportunity in Theoretical Physics at Maynooth!

Posted in Maynooth, The Universe and Stuff on May 21, 2022 by telescoper

Just a very quick reblog of this post because the deadline is tomorrow (22nd May) at 23.30. It’s a for a Lecturer (Assistant Professor) in Theoretical Quantum Physics, interpreted broadly to include quantum computation, quantum information theory, quantum many-body systems, quantum field theory, and applications thereof to condensed matter and high-energy physics, etc.

In the Dark

Just a short post passing on the information that we have a permanent Lectureship (Assistant Professorship) available in the Department of Theoretical Physics at Maynooth University. You can find the details, including a full Job Description and salary, here.

For the purposes of this position we interpret Quantum Physics broadly to include quantum computation, quantum information theory, quantum many-body systems, quantum field theory, and applications thereof to condensed matter and high-energy physics, etc.

This position is the first of several to be advertised across the Departments of Theoretical & Experimental Physics at Maynooth University, in areas including Astronomy and Earth Science, on top of this opportunity at Professorial level in Observational Astrophysics or Cosmology. Watch this space for more details!

The position is available from 1st September 2022 and the deadline for applications is 23.30 on Sunday 22nd May 2022 and you should apply through the Maynooth jobs…

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Science vs Marketing

Posted in Astrohype, Education, Science Politics, The Universe and Stuff with tags , , , on May 20, 2022 by telescoper

I saw a paper some months ago by former Sussex colleague Xavier Calmet and collaborators that attracted quite a lot of press coverage largely based on a press release from the University of Sussex that claimed:

Stephen Hawking’s famous black hole paradox solved after hair-raising discovery

(If you want to learn more about the black hole information paradox you could start here.)

The press release is pure unadulterated hype. The paper in Physical Review Letters is actually rather good in my opinion but it says next to nothing about the black hole information paradox. Unfortunately the Sussex press release was picked up by the BBC’s science editor Pallab Ghosh who turned it into a very garbled article. Unfortunately Ghosh has quite a lot of form when it comes to producing nonsensical takes on science results. See, for example, this piece claiming that recent results from the Dark Energy Survey cast doubt on Einstein’s general theory of relativity when they do nothing of the sort.

Fortunately in the case of the black hole paper David Whitehouse has done a good job at demolishing the “BBC’s black hole baloney” here so I don’t need to repeat the arguments.

What I will mention however is that there is an increasing tendency for university press offices to see themselves entirely as marketing agencies instead of informing and/or educating the public. Press releases about scientific research nowadays rarely make any attempt at accuracy – they are just designed to get the institution concerned into the headlines. In other words, research is just a marketing tool.

This isn’t the only aspect of the marketisation of universities. If an academic tries to organize a public engagement event or do some schools outreach activity, the chances are their institution will hijack it and turn it into a marketing exercise, aimed exclusively at student recruitment. Universities are increasingly unconcerned with education and research and obsessed with income.

Forget the phony controversies about woke politics and free speech manufactured by right-wing press. The real culture war in modern universities is between those who believe in the intrinsic value of higher education and those who see it simply as a means of generating profit by whatever means possible. As in any war, truth is the first casualty.

New Publication at the Open Journal of Astrophysics

Posted in Open Access, The Universe and Stuff on May 14, 2022 by telescoper

The last couple of days have been very busy but at last I’ve got time to announce a new publication in the Open Journal of Astrophysics! This one is the 5th paper in Volume 5 (2022) and the 53rd in all. It was published on Thursday in fact but I’ve only just found time to mention it here.

The latest publication is entitled “Statistical Uncertainties of the NDW=1 QCD Axion Mass Window from Topological Defects” and is written by Sebastian Hoof & Jana Riess of the Georg-August-Universität Göttingen in Germany and David Marsh of King’s College London.

This paper is in the Cosmology and Nongalactic Astrophysics folder (cross-listed on arXiv from High-Energy Physics).

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.

P.S. We have quite a number of papers out there waiting for revised versions to be submitted. I get the feeling that everyone is very busy these days. Hopefully as we emerge from the pandemic things will improve.

M87: Ring or Artefact?

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

Following on from yesterday’s post here is an arXiv preprint that I’ve only just seen, though it was submitted on Tuesday 10th May, ahead of yesterday’s announcement about Sagittarius A*. It says inside the manuscript (though not in the arXiv entry) that it was accepted for publication in ApJ on 5th May, though it has not yet appeared there.

The abstract is:

We report our independent image reconstruction of the M 87 from the public data of the Event Horizon Telescope Collaborators (EHTC). Our result is different from the image published by the EHTC. Our analysis shows that (a) the structure at 230 GHz is consistent with those of lower frequency VLBI observations, (b) the jet structure is evident at 230 GHz extending from the core to a few mas, though the intensity rapidly decreases along the axis, and (c) the unresolved core is resolved into bright three features presumably showing an initial jet with a wide opening angle of about 70 deg. The ring-like structures of the EHTC can be created not only from the public data, but also from the simulated data of a point image. Also, the rings are very sensitive to the FOV size. The u-v coverage of EHT lack about 40 micro-asec fringe spacings. Combining with a very narrow FOV, it created the 40 micro-asec ring structure. We conclude that the absence of the jet and the presence of the ring in the EHTC result are both artifacts owing to the narrow FOV setting and the u-v data sampling bias effect of the EHT array. Because the EHTC’s simulations only take into account the reproduction of the input image models, and not those of the input noise models, their optimal parameters can enhance the effects of sampling bias and produce artifacts such as the 40 micro-asec ring structure, rather than reproducing the correct image.

I draw your attention to the sentence “The ring-like structures of the EHTC can be created not only from the public data, but also from the simulated data of a point image”. In other words the authors (Miyoshi, Kato and Makino) are saying that the ring-like structure in the now-iconic image could be an artefact of the image reconstruction process as they can apparently be produced by a point source.

From the manuscript itself:

The EHTC conducted various surveys, but their methods were not objective and biased towards their desires from the very beginning of their analysis. They also failed to perform the basic data checking that VLBI experts always do.

That’s very blunt. The plot thickens!

It’s a lengthy paper and I haven’t gone through it in detail. Comments from experts are welcome through the box below.

Our own Galactic Black Hole

Posted in The Universe and Stuff with tags , , , , on May 12, 2022 by telescoper

As I mentioned a while ago the Event Horizon Telescope team held a press conference this afternoon and to nobody’s surprise they used it announce an image of the (shadow of the event horizon around the) black hole at the centre of the Milky Way.

Here it is:

You can read the full press release here.

You may recall a great deal of excitement about three years ago concerning the imaging of the “shadow” of the event horizon of the black hole in the centre of the galaxy M87. The question I was asked most frequently back then is that there’s a much closer black hole in the centre of our own Galaxy, the Milky Way, so why wasn’t that imaged first?

It it true is that the black hole in the centre of M87 is ~103 times further away from us than the black hole in the centre of the Milky Way – known to its friends as Sagittarius A* or SgrA* for short – but is also ~103 times more massive, so its Schwarzschild radius is ~103 times larger. In terms of angular resolution, therefore, the observational challenge of imaging the event horizon is similar in the two cases. However, in the the case of the Milky Way’s black hole the timescales involved are much shorter than in M87 and there is a greater level of obscuration along the line of sight. That’s why it took longer to produce the image.

It’s a very difficult observation of course and I’m not sure of the significance of the “lumps” you can see, but the dark region in the centre is what the image is really about and that seems to be exactly the predicted size. The resolution is about 20 microarcseconds. Congratulations to the Event Horizon Telescope team!

If you’re interested in learning more about how this image was made I recommend this short video:

The Brief Span of Life…

Posted in Art, Literature, The Universe and Stuff with tags , , on May 7, 2022 by telescoper

I found this rather poignant cartoon on Facebook because a friend shared it. Some people have told me they find it depressing. I don’t. I think the finiteness of life is one of the things that makes it bearable.

I don’t know the name of the artist. If anyone does please let me know.

Halley’s Comet last visited us in 1986 when I was 23 and living in Brighton. It will next be visible in 2061, when I shall be 98!

The comet’s orbital period of 75 years or so is brief by astronomical standards, as is the duration of a human life. As Quintus Horatius Flaccus (Horace to you and me) put it in one of his Odes (Book I, Ode 4, line 15):

Vitae summa brevis spem nos vetat incohare longam

A Road to Living Documents?

Posted in The Universe and Stuff, Open Access with tags on May 4, 2022 by telescoper

A few weeks ago I posted an item arguing that the scientific paper is an outdated concept and the whole business of research publishing should change to reflect more accurately how science is actually done. I’d argued previously that

the future for many fields will be defined not in terms of “papers” which purport to represent “final” research outcomes, but by living documents continuously updated in response to open scrutiny by the community of researchers. I’ve long argued that the modern academic publishing industry is not facilitating but hindering the communication of research. The arXiv has already made academic journals virtually redundant in many of branches of  physics and astronomy; other disciplines will inevitably follow.

I thought I would explain how the Open Journal of Astrophysics represents a small move in the direction of the “living document” idea.

Recently the author of a paper we published in 2019 contacted me to explain that readers had pointed some errors in that publication and he wished to amend it to correct the mistakes, which were typographical in nature but did propagate through a number of equations though they did not affect the main results. We had dealt with one post-publication amendment in the past and we handled this one in the same way:

  1. The author sent us a new version containing the proposed revisions;
  2. The Editor checked that they were reasonable (i.e. minor and without any significant changes to the scientific content);
  3. After getting the green light the author placed a revised version on arXiv with a comment explanation the revisions (in this case v3);
  4. We changed our overlay to point at the new version.

Here is the new overlay updated this morning.

You will see that there is a note on the overlay after the abstract. There is also a comment alongside the arXiv submission and another in the acknowledgements section of the revised paper. Owing to the separation between the overlay and the arXiv it is not necessary to change the Digital Object Identifier (DOI) or any of the article metadata.

This is a lot easier than the old-fashioned method of publishing an erratum. It may not represent the idea of a living document exactly, but it does demonstrate a way of feeding back to the publication after the “open scrutiny by the community of researchers” I referred to in my quote above.

It also demonstrates that peer review, however thorough, is never perfect and having wider scrutiny can find errors a referee might not.

Astronomical Heads Up

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

You may recall a great deal of excitement about three years ago concerning the imaging of the “shadow” of the event horizon of the black hole in the centre of the galaxy M87. There was so much interest in this measurement that you could hardly move without seeing this picture somewhere or other:

The question I was asked most frequently back then is that there’s a much closer black hole in the centre of our own Galaxy, the Milky Way, so why wasn’t that imaged first? The answer is that the black hole in the centre of M87 is about 1000 times further away from us than the black hole in the centre of the Milky Way – known to its friends as Sagittarius A* or SgrA* for short – but is also about 1000 times more massive, so its Schwarzschild radius is 1000 times larger. In terms of angular resolution, therfore, the observational challenge of imaging the event horizon is similar in the two cases.

I mention this because the Event Horizon Telescope team who made the above image are holding a press conference next week at ESO on “groundbreaking Milky Way results from the Event Horizon Telescope Collaboration”.

I wonder what these “groundbreaking results” might be?

Full Focus JWST!

Posted in The Universe and Stuff on April 29, 2022 by telescoper

I just saw a very welcome news item announcing that after months of work by the relevant teams, the James Webb Space Telescope is at last completely aligned, in full focus and all the associated instruments are working well. Here is a composite of images demonstrating this:

For reference here is a glossary of the abbreviations:

(NIRISS is actually coupled within the same module with the Fine Guidance Sensor (FGS) so they can be regarded as parts of the same instrument.)

Anyway, congratulations to everyone involved on this impressive achievement, which is a testament to a great deal of skill and hard work. The job isn’t over yet, of course, as there is still a great deal detailed testing and science validation to be carried out. No doubt we can look forward to some really exciting images from the commissioning period in due course!

Euclid Launch Concern

Posted in Politics, Science Politics, The Universe and Stuff with tags , , on April 27, 2022 by telescoper

I saw the following picture on Twitter. It was taken during a talk at the annual Euclid Consortium Meeting (which I am not at) and it gives a not -very-optimistic update about the timescale for the launch of Euclid.

Picture Credit: Hervé Aussel

I thought a delay in the launch was inevitable as soon as news broke of the Russian invasion of Ukraine (see here) because the original plan was to launch on a Russian Soyuz vehicle. The subsequent decision by the Russians to remove all their personnel from the launch site at Kourou (see here) made these even more likely, although according to the slide not certain.

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 payloads 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 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, which is what the last lines of the slide are about.

Being one of life’s pessimists I think a long delay is the likeliest outcome, though this is not based on any specific knowledge at all about the discussions going on and I’d be delighted to be proved wrong. I am now however seriously wondering whether Euclid will be launched before I retire!