New ESO chief Xavier Barcons (above) takes over from Tim de Zeeuw after a 10-year term.

ROMAN G. AGUILERA/EFE/Newscom

Top astronomer on the challenges of building the world’s largest telescope, and what’s next

Spanish astronomer Xavier Barcons took over the reins this month of the European Southern Observatory (ESO), the world’s foremost international astronomy organization. It is currently building the European Extremely Large Telescope (E-ELT), destined to be the world’s largest when completed in 2024.

In the 1980s Barcons set up the first x-ray astronomy group in Spain at the University of Cantabria. He is a specialist on active galactic nuclei, superbright galactic cores thought to be caused by giant black holes sucking in and heating up quantities of gas and dust. To study them, he’s been heavily involved in European x-ray space telescopes such as XMM-Newton and the forthcoming Athena, due for launch in 2028. Barcons has also worked at the University of Cambridge in the United Kingdom, Spain’s Council for Scientific Research, and served as chair of ESO’s council from 2012 to 2014.

He joins ESO in a period of high activity as the organization embarks on the E-ELT, its biggest project so far. But a shadow hangs over the €1.1 billion facility: Because of a shortfall in funding, the ESO council has only approved a first phase of construction, which will produce a working telescope but with certain desired components delayed until extra funding can be found. Those components include 210 of the 798 segments that make up the 39-meter main mirror, back-up mirror segments, some lasers for the adaptive optics system, and a few instrument components. 

Meanwhile, ESO’s current main facility, the Very Large Telescope (VLT) at Cerro Paranal in Chile, continues to be the world’s most productive ground-based instrument, and the Atacama Large Millimeter/submillimeter Array (ALMA), a new radio observatory built jointly with North American and East Asian countries, is opening up this previously little-studied window on the universe. 

Barcons spoke with ScienceInsider by phone from his office at ESO headquarters in Garching, Germany. His responses have been edited for clarity and brevity.

Q: What is happening at the E-ELT site in Cerro Paranal right now?

A: In the past few months we handed over the mountain to the construction company that will build the E-ELT structure. Earlier a road was built and the top was flattened and a power line to the Chilean grid was installed. We’re now well placed for construction. There is a lot going on in industry, too, starting the fabrication of mirror segments and instruments.

Q: What are the prospects for finding extra funding so that the second phase of construction can be completed?

A: We’re looking for options. We could expand the number of member states [now 15 European nations plus Chile]; we’re actively discussing with two European countries and have signed a cooperation agreement with Australia. Australia will only be part of VLT but it will help with our finances. We wish Australia would become a member state. It has so much to offer; its astronomical community is very skilled. It’s a win-win situation. We’re also exploring other options: reducing costs, finding synergies.

Of the several items in phase II, the most critical is completing the mirror. Although it will retain its 39-meter outer diameter, phase one will leave a hole in the middle. In June the council approved design work for the full mirror and we’re hoping for authorization to build it. We need to make that happen. Of the other items [in phase two], none are time critical at the moment. They’re modular, we can decide later.

Q: Originally, Brazil joining ESO was to have provided the necessary E-ELT funding. Are there any signs of that happening? 

A: The Brazilian parliament ratified the [accession] treaty in 2015. The procedure is completed. It’s up to the government to decide when to implement it. I haven’t seen much progress recently but it’s at the top of my list to conclude this process in the near future. No projects depend on it happening.

Q: With facilities getting increasingly large and expensive, might ESO collaborate again globally as it did with ALMA?

A: That could be possible for some projects. I’m extremely proud of ALMA. It’s a really unique machine and we couldn’t have done it alone and neither could the other partners. I’m sure there will be opportunities to collaborate on other projects but we’re very busy, we can’t start any new significant opportunities until E-ELT is well underway.

Q: One of E-ELT’s rivals, the Thirty Meter Telescope (TMT), is struggling to secure its site on Mauna Kea in Hawaii because of local opposition. If the project collapses, what impact will the absence of a giant telescope in the Northern Hemisphere have for astronomy?

A: It would not be a catastrophe; we only have ALMA in the south. But it would be much better to have two in the south [E-ELT and the Giant Magellan Telescope] and one in the north, in Hawaii or elsewhere. [The TMT has identified the Canary Islands as a possible alternative.] We’ve offered all possible help to assist [the TMT] to make it become a reality. But purely from a scientific point of view, it’s better to have north and south coverage.

Q: After E-ELT, what’s next for ESO?

A: I don’t know at the moment, although astronomers dream about this night and day. There are some ideas on the table, including a reasonably sized spectroscopic telescope, a large submillimeter antenna to supplement ALMA, and maybe an expansion of the VLT interferometer. We have no opportunity to start anything in the near future, but I’m sure there will be a good battery of proposals when the time comes.