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February 3, 2023



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Points of view: Mariano Moles


Mariano Moles is a member of the Gran Telescopio CANARIAS' (GTC's) Scientific Advisory Committee (SAC), which advises the governing bodies of the GTC and GRANTECAN's Project Director about the scientific requirements of the telescope.

A Doctor of Astrophysics, Mariano Moles is currently Research Professor at the Instituto de Astrofísica de Andalucía (IAA), of which he is a former Director. His previous positions include Director of the Spanish-German Observatorio de Calar Alto and Research Professor at the Instituto de Matemáticas y Física Fundamental (IMAFF, Institution of Mathematics and Fundamental Physics). He has also worked at the Institut d’Astrophysique de Paris (IAP) and the Observatorio Astronómico Nacional (OAN).

As a member of the SAC, Moles' responsibilities include establishing the GTC instrumentation programme, determining its priorities and defining the selection process.


As a member of the Scientific Advisory Committee, could you update us on how the GTC and instruments are progressing?

There’s a great deal of hope and optimism that the GTC will soon be operational, but we mustn’t forget that it is an extremely complicated and ground-breaking telescope. There are no off the shelf solutions - we have to come up with them as we go. In this kind of big science projects there is a constant dealing with problems as and when they arise. Work on OSIRIS and CanariCam, the first light instruments, is going smoothly as far as we can tell. They are on time and they will be ready for delivery at the telescope when it is ready to go into operation.

The first workshop on “Science with the GTC” was held last year and a second is due to be held soon. What can we expect to see this time?

A telescope like this can do such extraordinary things that we have to plan what we want to present, we can’t just improvise. These workshops are aimed at showing the state of astronomy today - what is being done with similar telescopes that are starting operations and how we, the Spanish community, as well as the international community, can make contributions worthy of the scale of the equipment we are going to work with.

That’s what we did in Granada, and we will do the same in Mexico - showcase what is being done, what can be done, how we can work effectively and help to drive progress in astronomy worldwide.

Which do you think will be the most interesting projects?

It depends, everyone will have their own favourite. Certainly, there are two areas of work that stand out as the most important (in my opinion and without disparaging the others) for these kinds of instruments.

The first of these is the deep Universe, redshift and very faint other words, reaching out into the younger Universe. The second is the search for very low mass objects, stars and extrasolar planets. It is in these areas that this powerful instrument will really make its mark, and that is not to detract from the very many other ideas and projects that will surely be developed.

What do you think of the latest theories on vacuum energy?

It’s one of my favourite subjects. The paradigm of an expanding Universe has been well-discussed in the past, but talking about the cosmological constant was a purely academic pursuit even as recently as ten years ago and no-one thought about it very much. However, type Ia supernova measurements and, more recently, interpretations of the root data used to produce maps of the cosmic background seem to suggest - and I stress the word “seem” - not only that the cosmological constant exists but that it also has a positive value.

Theoretically speaking, this is just another element of a model that is completely accepted; in physical terms, however, it is extremely complicated to interpret.

Let’s imagine that right now, with the data such as it is (and a lot of it is only sketched in as things are changing very quickly and none of this is well-founded theory) we have a cosmological constant with the value that the data seem to be suggesting. This would point towards rapidly accelerating expansion and, given the relative roles of material and gravity - which tend to contract the Universe - and expansion, related to the cosmological constant, which tends to cause the Universe to break up more and more rapidly, we could conclude that the Universe is entering a new stage of inflation - accelerated expansion - but this time with nothing to counteract it, so that it must ultimately result in a final disintegration.

I repeat, this is a literal interpretation of the facts as they appear to be right now. In reality it is much more complex - the data are much less clear than the summaries and interpretations we are basing on them and the whole issue is still very much under discussion.

However if these data lead us to a model of the Universe where the cosmological constant accounts for 70 per cent of everything, with just 30 per cent being material, then its influence becomes overwhelming, expansion runs out of control with the result that we move quite literally into a final phase of inflation.

Natalia R. Zelman

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