La Palma picked as alternate site for embattled Thirty Meter Telescope

If Mauna Kea, Hawaii, doesn’t pan out for the Thirty Meter Telescope (TMT), the $1.4 billion facility will move to La Palma, one of Spain’s Canary Islands. The selection of the alternate site was announced by the TMT international board on 31 October. A decision on whether to stay will be made in the next year, in time to begin construction at either site in April 2018.

The TMT collaboration selected the Hawaiian site in 2009. Although the collaboration tried to proceed with sensitivity about the concerns of some native Hawaiians, opposition to the telescope began to spiral in spring 2015 (see Physics Today, July 2016, page 31 ).

In Hawaii, the project is currently enmeshed in permit hearings. Even if those are sorted out soon, staunch opponents have sworn to use every tactic possible to delay the project.

Enter Roque de los Muchachos Observatory (ORM) on the Canary Islands. The La Palma site, at an elevation of about 2250 m, beat out four other candidates in the Northern Hemisphere and in Chile, where two similarly sized telescopes—the 39 m European Extremely Large Telescope and the 25 m Giant Magellan Telescope—are already under construction.

All the candidate sites would be excellent in terms of astronomical capability, says Fiona Harrison, a Caltech astrophysicist and member of the TMT board. “The TMT can meet its scientific objectives,” she says. And considering that the world’s two other gigantic telescopes are getting built south of the equator, siting the TMT in the Northern Hemisphere expands the visible universe.

Mauna Kea is still the top choice: It is higher and colder, and its atmosphere is less turbulent than at La Palma. Making IR observations and removing atmospheric effects will be more challenging if the telescope is relocated. The selection of ORM came down to the existing infrastructure, Harrison says. The available roads, housing, and fast digital communications will keep down costs and time to completion.

On La Palma, the TMT would become the granddaddy among a dozen or so optical, IR, and Cherenkov telescopes. TMT scientists would have access to offices and laboratories at a sea-level site on La Palma and on neighboring Tenerife island, home to the Teide Observatory’s solar and microwave telescopes. The observatories on both islands are run by the Institute of Astrophysics of the Canary Islands.

The observatories, the islands, and the Spanish government would welcome the TMT with open arms. Rafael Rebolo, the institute’s director, estimates that the giant telescope would bring roughly $25 million a year to the Canary Islands in jobs and industry contracts. Most important, he says, “it will give us a tremendous opportunity to participate in scientific discovery.”