Join us here for a few highlights of TMT and how it's the best in the world at what it does.
... TMT's dome is incredibly compact and efficient!
Even though TMT’s mirror is more than 13 times larger in surface area than Gemini’s, its dome is only slightly bigger—about 20% in height. In fact, it’s the smallest dome among the three Extremely Large Telescopes. This graphic compares the heights of these domes with that of Gemini, a well-known 8 meter telescope. TMT’s dome has a smooth, curved design that helps reduce wind shake, which can blur images. By keeping the telescope steady, TMT can capture sharper, clearer views of the universe. Plus, its shape and color were chosen to help it blend in better with the surrounding environment.
... TMT’s mirror design is the most efficient of the Extremely Large Telescopes.
90% of the TMT's mirror diameter collects light that is sent directly to its instruments, maximizing the amount of data astronomers can use. This efficiency comes from a smart design: smaller gaps between mirror segments, a smaller central opening, and ultra-thin supports for the secondary mirror. These features reduce the amount of starlight that gets scattered, allowing TMT to capture more light and focus it more precisely. This results in sharper, clearer images, helping scientists study distant planets, galaxies, and other celestial objects in incredible detail.
The TMT mirror has 90% of the surface area of its diameter collecting light, as opposed to 82% for the E-ELT and 70% for GMT.
TMT is ideally suited for finding extrasolar planets!
Its diffraction-limited point spread function, which determines how precisely the telescope focuses light from a distant star, makes it particularly effective for detecting planets orbiting close to their host stars—one of TMT’s primary science objectives.
The central core of a telescope’s point spread function becomes narrower as the primary mirror diameter increases. Since the E-ELT has the largest mirror, it produces the narrowest core, while Keck, with a smaller mirror, has the widest core. However, not all light is concentrated in the core; some spreads into rings and side lobes.
TMT’s aperture has the smallest gaps, resulting in a smoother and more uniform diffraction pattern than the other telescopes with larger gaps. This well-structured diffraction pattern enhances TMT’s ability to detect planets closer to their host stars with greater precision, accuracy, and clarity.
TMT's optical design is highly efficient.
TMT uses three mirrors to direct light from the sky to its instruments, whereas the European Extremely Large Telescope (E-ELT) uses five or even six mirrors. With fewer mirrors, TMT loses less light, ensuring more light reaches the instruments for analysis. GMT uses at least two mirrors for its direct Gregorian focus and three mirrors for its folded Gregorian instruments.
This efficient design also helps reduce thermal emission from the telescope itself—since all objects emit a faint glow in the near-infrared. By minimizing this unwanted background noise, TMT improves its ability to observe the faintest and reddest light in the universe with greater clarity.
TMT’s preferred Maunakea, Hawaiʻi site is the world’s premier location for adaptive optics!
Adaptive optics corrects for most of the atmospheric distortion that blurs images, allowing ground-based telescopes to capture images even sharper than those from space-based telescopes.
The table to the left compares key site characteristics for TMT on Maunakea, the E-ELT, and GMT, with highlighted boxes showing the best values for astronomical observations. Many of these characteristics are directly linked to adaptive optics performance and clearly show TMT’s preferred site on Maunakea the best in the world for adaptive optics!
TMT makes the most out of its mirror!
A telescope’s mirror diameter helps determine how sharp its images are, but it’s the collecting area, the part of the mirror that actually gathers light, that lets astronomers study the faintest objects in the universe. TMT’s 30 meter primary mirror is designed with minimal gaps between segments and a smaller central shadow from its secondary mirror, allowing it to collect light as efficiently as a 28.4-meter unobstructed mirror.
Each of the ELTs has a unique design tailored to its scientific goals. The Giant Magellan Telescope (GMT), with its 25.4 meter segmented mirror, is optimized for certain observing strategies but has more space between its segments, resulting in a light-collecting area similar to that of a 21.3 meter unobstructed mirror. The European Extremely Large Telescope (E-ELT), with the largest mirror at 39 meters, achieves a collecting area equivalent to a 35.3 meter unobstructed mirror.
TMT’s efficient optical design was purposefully chosen to maximize the science return from its full aperture, ensuring exceptional sensitivity and the ability to observe some of the faintest and most distant objects in the cosmos.
