Planerat megateleskop kan få nytt hem på La Palma

The Thirty Meter Telescope (TMT) is a proposal for an extremely large telescope (ELT), intended to be built on Mauna Kea, on the island of Hawai'i. The TMT would become the largest visible-light telescope on Mauna Kea. Scientists have been considering ELTs since the mid 1980s. In 2000, astronomers considered the possibility of a telescope with a light-gathering mirror larger than 20 meters (66 ft) in diameter, using either small segments that create one large mirror, or a grouping of larger 8-meter (26 ft) mirrors working as one unit. The US National Academy of Sciences recommended a 30-meter (98 ft) telescope be the focus of U.S. interests, seeking to see it built within the decade. Scientists at the University of California, Santa Cruz and Caltech began development of a design that would eventually become the TMT, consisting of a 492-segment primary mirror with nine times the power of the Keck Observatory. Due to its light-gathering power and the optimal observing conditions which exist atop Mauna Kea, the TMT would enable astronomers to conduct research which is infeasible with current instruments. The TMT is designed for near-ultraviolet to mid-infrared (0.31 to 28 μm wavelengths) observations, featuring adaptive optics to assist in correcting image blur. The TMT would be at the highest altitude of all the proposed ELTs. The proposed location on Mauna Kea has been controversial among the Native Hawaiian community and spawned a series of protests. Demonstrations attracted press coverage after October 2014, when construction was temporarily halted due to a blockade of the roadway. When construction of the telescope was set to resume, construction was blocked by further protests each time. In 2015, Governor David Ige announced several changes to the management of Mauna Kea, including a requirement that the TMT's site will be the last new site on Mauna Kea to be developed for a telescope. The Board of Land and Natural Resources approved the TMT project, but the Supreme Court of Hawaii invalidated the building permits in December 2015, ruling that the board had not followed due process. In October 2018, the Court approved the resumption of construction; however, no further construction has occurred due to continued opposition. In July 2023 a new state-appointed oversight board, which includes Native Hawaiian community representatives and cultural practitioners, began a five-year transition to assume management over Mauna Kea and its telescope sites, which may be a path forward. In April 2024, TMT's project manager apologized for the organization having "contributed to division in the community", and stated that TMT's approach to construction in Hawai'i is "very different now from TMT in 2019." An alternate site for the Thirty Meter Telescope has been proposed for La Palma, Canary Islands, Spain, but is considered less scientifically favorable by astronomers. In June 2025 the United States' National Science Foundation dropped support for the TMT in favor of the Giant Magellan Telescope. This lack of funding puts the TMT's future in doubt, although the scientists in the TMT international consortium said they would press forward.