The Thirty Meter Telescope (TMT) is a planned extremely large telescope (ELT) that has become controversial due to its location on Mauna Kea, on the island of Hawaiʻi. The TMT would become the largest visible-light telescope on Mauna Kea.
An artist's rendering of proposed telescope
The Thirty Meter Telescope design, late 2007
Cultural practitioner Joshua Lanakila Mangauil, along with Kahoʻokahi Kanuha and Hawaiian sovereignty supporters block the access road to Mauna Kea in October 2014, demonstrating against the building of the Thirty Meter Telescope.
Inverted flag being flown next to Mauna Kea access road as a sign of protest, September 2023
Extremely large telescope
An extremely large telescope (ELT) is an astronomical observatory featuring an optical telescope with an aperture for its primary mirror from 20 metres up to 100 metres across, when discussing reflecting telescopes of optical wavelengths including ultraviolet (UV), visible, and near infrared wavelengths. Among many planned capabilities, extremely large telescopes are planned to increase the chance of finding Earth-like planets around other stars. Telescopes for radio wavelengths can be much bigger physically, such as the 300 metres aperture fixed focus radio telescope of the Arecibo Observatory. Freely steerable radio telescopes with diameters up to 100 metres have been in operation since the 1970s.
Image: Latest Rendering of the E ELT
Image: Top view of tmt complex
Image: Giant Magellan Telescope artist's concept
The domes of the ELT, the TMT and the GMT compared to other well-known telescopes
