Archive for Euclid

R.I.P. Olivier Le Fèvre (1960-2020)

Posted in The Universe and Stuff with tags , , , , , on June 29, 2020 by telescoper

Olivier Le Fèvre (1960-2020)

The international cosmological community was deeply saddened last week to hear of the death on 25th June after a long illness of Olivier Le Fèvre. He was 59 years old.

Olivier was a specialist in astronomical spectroscopy and as such he made important contributions to cosmology through galaxy redshift surveys. He was Director of the Laboratoire d’Astrophysique de Marseille from 2004 to 2011. In latter years he was involved, among many other things, in the Euclid space mission.

You can find a full obituary and appreciation of Olivier’s life and work here. His funeral takes place this morning and there is an online book of condolence here to send messages of condolence and support to his family, friends and colleagues at this difficult time.

Rest in peace, Olivier Le Fèvre (1960-2020).

Euclid Updates

Posted in The Universe and Stuff with tags , , , , on June 17, 2019 by telescoper

Following the Euclid Consortium Meeting in Helsinki a couple of weeks ago, here are a couple of updates.

First, here is the conference photograph so you can play Spot The Telescoper:

(The picture was taken from the roof of the Finlandia Hall, by the way, which accounts for the strange viewpoint.

The other update is that the European Space Agency has released a Press Release releasing information about the location on the sky of the planned Euclid Deep Fields. Here they are (marked in yellow):

These deep fields amount to only about 40 square degrees, a small fraction of the total sky coverage of Euclid (~15,000 square degrees), but the Euclid telescope will point at them multiple times in order to detect very faint distant galaxies at enormous look-back times to study galaxy evolution. It is expected that these fields will produce several hundred thousand galaxy images per square degree…

Selecting these fields was a difficult task because one has to avoid bright sources in both optical and infrared (such as stars and zodiacal emission) so as not to mess with Euclid’s very sensitive camera. Roberto Scaramella gave a talk at the Helsinki Meeting showing how hard it is to find fields that satisfy all the constraints. The problem is that there are just too many stars and other bits of rubbish in the sky getting in the way of the interesting stuff!


For much more detail see here.


Equality, Diversity and Euclid

Posted in The Universe and Stuff with tags , , on June 7, 2019 by telescoper

So here I am, back in my hotel, after the second pleasant wine and food reception of the week – this time hosted by the University of Helsinki. I have to leave early tomorrow morning to get back to Maynooth so I’m not among those going for dinner afterwards.

It’s been a very satisfying meeting, in terms of scientific content, organization and even the weather which has been warm and sunny throughout.

That said I feel obliged to mention one less than satisfactory episode which happened this afternoon. Euclid is a very large consortium working on a complex mission. That requires certain management structures to be put in place, including how to deal with the many scientific publications that will hopefully result from the Euclid mission to be as fair as possible to everyone working on the various projects as well as ensuring the scientific quality of resulting papers.

This afternoon a very distinguished senior member of the Euclid Consortium presented an overview of the publication policy on behalf of the Editorial Board which included this slide:

Not knowing all the names I didn’t think twice about the various panels until at the end of the talk a member of the audience pointed out that none of the individuals named are female.

I wasn’t alone in being surprised that such a situation had arisen, especially since Euclid has a Diversity Committee. But what made matters worse was the apparently dismissive response of the speaker, which caused a sharp intake of breath around the auditorium, and left many with the impression that the Consortium needs to look at whether unconscious or other bias might have been involved in the selection of these members. The impression given may have been inadvertent but appearances matter, and I know I’m not the only person who was troubled by what went on this afternoon. I sincerely hope the Diversity Committee looks into this issue as soon as possible.

UPDATE: 21st June 2019. I understand that this issue has been looked into in depth by the Euclid Consortium and active measures are being taken to improve the gender balance in future, which is a very positive outcome.

Notes from Euclid 2019

Posted in Biographical, Maynooth, The Universe and Stuff with tags , , , , on June 4, 2019 by telescoper

I’ve just had my breakfast so I thought I’d do a quick post before the start of play on of the 2019 Euclid Consortium Meeting in Helsinki. Previous Euclid Consortium meetings were held in: Bologna (2011); Copenhagen (2012); Leiden (2013); Marseille (2014); Lausanne (2015); Lisbon (2016); London (2017); and Bonn (2018). I’ve only attended the last two: I was non-Euclidean before that.

Finlandia Hall

The venue is the Finlandia Hall, which looks splendid from the outside. I passed it during my stroll yesterday afternoon just so I could be sure where it is. It’s easy to find as it is very central and on the edge of a lake next to a major thoroughfare (Mannerheimintie). . I arrived yesterday to beautiful sunny weather but that has changed – it is pouring down as I write this, with thunder and lightning to boot. I don’t have to leave the Hotel for an hour or so, however, so perhaps it will have passed. There’s no sign of that just yet but I brought a brolly, and it’s only 15 minutes away from the Hotel on foot.

According to the web page there are 408 participants at the last count. I expect there’ll be quite a few people I know here but I haven’t met any yet. The Euclid Consortium has well over a thousand members, but obviously they’re not all here this week. I seem still to be the only representative of Ireland.

There’s a nice webpage showing all the institutions around the world who belong to the consortium behind the European Space Agency’s Euclid Mission. Here’s a screen grab that shows all the logos of all the institutions involved in this very large Consortium:

There are so many that it’s hard to see them all, but if you look very closely about half way down, among the Ms, you will see Maynooth University among them. Ireland is a member state of the European Space Agency, by the way.

Top tips for participants include not to tip:

Here is the latest timeline for the Euclid mission: launch around June 2022 followed by six years of operations.

If you want to follow on Twitter the relevant hashtag is #Euclid2019.

The Future Circular Collider: what’s the MacGuffin?

Posted in Science Politics, The Universe and Stuff with tags , , , , , , , on February 7, 2019 by telescoper

I’ve been reading a few items here and there about proposals for a Future Circular Collider, even larger than the Large Hadron Collider (and consequently even more expensive). No doubt particle physicists interested in accelerator experiments will be convinced this is the right move, but of course there are other projects competing for funds and it’s by no means certain that the FCC will actually happen.

One of the important things about `Big Science’ when it gets this big is that it has to capture the imagination of people with political influence if it is to be granted funding. Based on past experience that means that there has to be a Big Discovery to be made or a Big Idea to be tested. This Big Thing has to be simple enough for politicians to understand and exciting enough to capture their imagination (and that of the public). In the case of the Large Hadron Collider (LHC), for example, this was the Higgs Boson. In the case of the Euclid space mission, the motivation is Dark Energy.

The Big Thing that sells a project to politicians is not necessarily the thing that most scientists are interested in. The LHC has done a lot of things other than discover the Higgs, and Euclid will do many things other than probe Dark Energy, but there has to be one thing to set it all in motion. It seems to me that the Big Question about the FCC is whether there is something specific that can motivate this project in the way the Higgs did for the LHC? If so, what is it?

Answers on a postcard or, better, through the comments box below.


Humphrey Bogart with the eponymous Maltese Falcon

Anyway, these thoughts reminded me of the concept of a  MacGuffin. Unpick the plot of any thriller or suspense movie and the chances are that somewhere within it you will find lurking at least one MacGuffin. This might be a tangible thing, such the eponymous sculpture of a Falcon in the archetypal noir classic The Maltese Falcon or it may be rather nebulous, like the “top secret plans” in Hitchcock’s The Thirty Nine Steps. Its true character may be never fully revealed, such as in the case of the glowing contents of the briefcase in Pulp Fiction , which is a classic example of the “undisclosed object” type of MacGuffin, or it may be scarily obvious, like a doomsday machine or some other “Big Dumb Object” you might find in a science fiction thriller.

Or the MacGuffin may not be a real thing at all. It could be an event or an idea or even something that doesn’t actually exist in any sense, such the fictitious decoy character George Kaplan in North by Northwest. In fact North by North West is an example of a movie with more than one MacGuffin. Its convoluted plot involves espionage and the smuggling of what is only cursorily described as “government secrets”. These are the main MacGuffin; George Kaplan is a sort of sub-MacGuffin. But although this is behind the whole story, it is the emerging romance, accidental betrayal and frantic rescue involving the lead characters played by Cary Grant and Eve Marie Saint that really engages the characters and the audience as the film gathers pace. The MacGuffin is a trigger, but it soon fades into the background as other factors take over.

Whatever it is or is not, the MacGuffin is responsible for kick-starting the plot. It makes the characters embark upon the course of action they take as the tale begins to unfold. This plot device was particularly beloved by Alfred Hitchcock (who was responsible for introducing the word to the film industry). Hitchcock was however always at pains to ensure that the MacGuffin never played as an important a role in the mind of the audience as it did for the protagonists. As the plot twists and turns – as it usually does in such films – and its own momentum carries the story forward, the importance of the MacGuffin tends to fade, and by the end we have usually often forgotten all about it. Hitchcock’s movies rarely bother to explain their MacGuffin(s) in much detail and they often confuse the issue even further by mixing genuine MacGuffins with mere red herrings.

Here is the man himself explaining the concept at the beginning of this clip. (The rest of the interview is also enjoyable, convering such diverse topics as laxatives, ravens and nudity..)

There’s nothing particular new about the idea of a MacGuffin. I suppose the ultimate example is the Holy Grail in the tales of King Arthur and the Knights of the Round Table in which the Grail itself is basically a peg on which to hang a series of otherwise disconnected stories. It is barely mentioned once each individual story has started and, of course, is never found. That’s often how it goes with MacGuffins -even the Maltese Falcon turned out in the end to be a fake – they’re only really needed to start things off.

So let me rephrase the question I posed earlier on. In the case of the Future Circular Collider, what’s the MacGuffin?

Euclid, by Max Ernst

Posted in Art with tags , , on December 18, 2018 by telescoper

by Max Ernst (1891-1976) , painted in 1945 (oil on canvas, 65 x 57.5 cm).


Euclid 2018: Day 3

Posted in Biographical, The Universe and Stuff with tags , , on June 14, 2018 by telescoper

It’s the morning after the conference dinner the night before, so as Day 4 of the Euclid Consortium meeting gets under way I’ve just got the time and bandwidth to do a brief post about the events of yesterday. First of all, the conference photo arrived and is shown above. You’d be hard pressed to spot me in it, as there are a lot of people in it (and bear in mind that only about a quarter of the membership of the Euclid Consortium are actually present here in Bonn).

Yesterday I went to splinter meetings related to the working groups on cross-correlating Euclid with cosmic microwave background data (morning) and clusters of galaxies (afternoon). The latter session produced the following diagram, which makes everything clear:

After the day’s work was done I took a walk down to the western bank of the Rhine (just about 15 minutes’ walk from my hotel), on the way to the conference dinner at the . Sadly, I didn’t see any Rhine Maidens or find any gold to make into a ring.

Anyway, the dinner was at the splendid Rhein Hotel Dreesen and I had the good fortune to sit with some Italian friends from way back – by which I mean over 20 years!

Fortunately I didn’t have far to go to get back to my hotel after the festivities!

Euclid2018: Highlights of Day 2

Posted in Biographical, The Universe and Stuff with tags , , , on June 13, 2018 by telescoper

I’ve just had my breakfast so I thought I’d do a quick post before the start of play at Day 3 of the 2018 Euclid Consortium Meeting in Bonn.

Day 2 was largely devoted to updates from the various Science Working Groups, but there was also an important presentation from Jason Rhodes about WFIRST, which is in some ways a rival to Euclid, or perhaps a complementary mission depending on how you look at it.

There was dismay in the global astronomy community last year when Donald Trump proposed taking the axe to WFIRST but it was good to hear that Congress not only reversed his decision but granted it additional funds over and above the original request.

Among the SWG updates was one by Alessandra Silvestri from the Theory Working Group concentrating on how Euclid could be used to test cosmology beyond the standard model. She focussed quite a lot on Horndeski Gravity, which is the most general four-dimensional scalar-tensor theory that leads to equations of motion that have the form of second-order differential equations.

Towards the end of the day there was a session devoted to the award of the Euclid Star Prizes.

The individual awards went to Micaela Bagley, Carmelita Carbone, Teake Nutma, Bertrand Morin, and Stefanie Wachter; more details on the winners and the awards they won will be posted here. The team award was given to the Flagship simulation team. Coincidentally, I posted about the Flagship simulations last year. Much of the preparation for Euclid would be impossible without these simulations, and the award of a prize to the team is very well justified.

The day finished with short talks from each of the prizewinners. That brought to the end two days of plenary sessions in the big hall of the Stadthalle. The next two days will be the `Splinter sessions’ which are held in parallel.

Oh, and one other thing: the 2019 Euclid Consortium Meeting will be held in Helsinki from June 4-7. Looks like I’ll be spending my birthday in Finland next year!

P.S. Previous Euclid Consortium meetings were: Bologna (2011);  Copenhagen (2012); Leiden (2013); Marseille (2014);  Lausanne (2015); Lisbon (2016); and London (2017).

Euclid’s Flagship Simulation

Posted in The Universe and Stuff with tags , , on July 28, 2017 by telescoper


Credit: J. Carretero/P. Tallada/S. Serrano for ICE/PIC/U.Zurich and the Euclid Consortium Cosmological Simulations Science Working Group.

The above image is taken from the world’s largest simulated galaxy catalogue, which has been constructed to help prepare for the  forthcoming Euclid space mission. The image actually shows only a small part of the full Euclid Flagship mock galaxy catalogue, which contains more than 2 thousand million galaxies distributed over the 3-dimension cosmological volume that Euclid will survey. Synthetic galaxies in this simulation mimic with great detail the complex properties that real sources display: ranging from their shapes, colours, luminosities, and emission lines in their spectra, to the gravitational lensing distortions that affect the light emitted by distant galaxies as it travels to us. The simulation is large enough to allow full `light-cone’ effects to be taken into account, as the look-back time to the edge of the Euclid survey volume is long enough for significant evolution to have occurred; according to the standard cosmological model, the time taken for light to travel from redshift z=2.3 to now is about 10.8 billion years, a significant fraction of the age of the Universe.

`Mock’ catalogues like this are needed to plan large observational programmes, whether using space missions or ground-based facilities, and to help prepare the data analysis strategies and tools needed to deal with the real data when it arrives. They can also be used to make excellent images for PR and outreach purposes.

The use of the word `simulation’ always makes me smile. Being a crossword nut I spend far too much time looking in dictionaries but one often finds quite amusing things there. This is how the Oxford English Dictionary defines SIMULATION:


a. The action or practice of simulating, with intent to deceive; false pretence, deceitful profession.

b. Tendency to assume a form resembling that of something else; unconscious imitation.

2. A false assumption or display, a surface resemblance or imitation, of something.

3. The technique of imitating the behaviour of some situation or process (whether economic, military, mechanical, etc.) by means of a suitably analogous situation or apparatus, esp. for the purpose of study or personnel training.

So it’s only the third entry that gives the meaning intended to be conveyed by the usage in the context of cosmological simulations. This is worth bearing in mind if you prefer old-fashioned analytical theory and want to wind up a simulationist!

In football, of course, you can even get sent off for simulation…

The Great Dark Energy Poll

Posted in The Universe and Stuff with tags , , on June 8, 2017 by telescoper

Yesterday was a very busy day: up early to check out of my hotel and head to the third day of the Euclid Consortium meeting for the morning session, then across to the Institute of Physics for a Diversity and Inclusion Panel meeting, then back to the Euclid Consortium meeting for the last session of the day, then introducing the two speakers at the evening event, then to Paddington for the 7.15 train back to Cardiff. I was not inconsiderably tired when I got home.

I had to bale out of the evening session to get the train I was booked on, but it seemed to be going well. Before I left, Ofer Lahav asked for an informal show of hands about a few possibilities relating to the nature of Dark Energy. Since today is polling day for the 2017 General Election, I thought it might be a good idea to distract people from politics for a bit by running a similar poll on here.

There are lots of possibilities for what dark energy may turn out to be, but I’ve decided to allow only six broad classes into which most candidate explanations can be grouped:

  1. The cosmological constant, originally introduced as a modification of the left hand side of Einstein’s general theory of relativity – the side that describes gravity – but more often regarded nowadays as a modification of the right-hand-side representing a vacuum energy. Whichever interpretation you make of this, its defining characteristic  is that it is constant.
  2.  Modified gravity,  in other words some modification of the left-hand-side of Einstein’s equations that manifests itself cosmologically which is more complicated than the cosmological constant.
  3. Dynamical dark energy, i.e. some other modification of the energy-momentum tensor on the right-hand side of Einstein’s equation that looks like some form of “stuff” that varies dynamically rather than being cosmologically constant.
  4.  Violation of the cosmological principle by the presence of large-scale inhomogeneities which result in significant departures from the usual Friedman-Robertson-Walker description within which the presence of dark energy is
  5. Observational error, by which I mean that there is no dark energy at all: its presence is inferred erroneously on the basis of flawed measurements, e.g. failure to account for systematics.
  6.  Some other explanation – this would include the possibility that the entire standard cosmological framework is wrong and we’re looking at the whole thing from the wrong point of view. If you choose this option you might want to comment through the box below what you have in mind.

Well, there are the six candidates. Make your choice: