I dream of witnessing a universe no one has ever seen. Of uncovering celestial objects so distant, they defy the limits of imagination. And ultimately, of reaching the very first luminous structures born in the dawn of the cosmos. This isn’t just the ambition of astronomers—it’s a romantic vision shared by all of humanity in the modern age. 

ULTIMATE is a bold endeavor to peer into the universe’s infancy. The Subaru Telescope has already pioneered wide-field surveys of the distant universe. With ULTIMATE, we take the next step—harnessing its extraordinary sensitivity in the near-infrared, especially around 2μm, and aligning our efforts with upcoming space missions such as Euclid (ESA) and the Nancy Grace Roman Space Telescope (NASA). Together, we aim to unravel the mysteries of the universe’s first structures—through the power of observation and the spirit of discovery.

Many people have looked at images of galaxies and thought, “How beautiful.” But have you ever wondered how galaxies came to acquire such magnificent appearances? ULTIMATE will trace back through cosmic history and clearly depict the formation and evolution of galaxies. Not only will it identify distant galaxies, but thanks to its high spatial resolution, ULTIMATE will also be able to reveal the internal structures of individual galaxies in the distant universe. For nearby galaxies, it will resolve structures down to the scale of giant molecular clouds. For objects within our Milky Way, it can go even further, down to individual stars—allowing us to grasp the physical phenomena occurring inside galaxies with incredible clarity. By thoroughly dissecting galaxies across different epochs, ULTIMATE will reveal the true nature of these celestial systems.

Though space may appear quiet, it is far from inactive. Explosive events are happening throughout the universe. By conducting wide-field, high-sensitivity monitoring observations with ULTIMATE, we may be able to detect supernova explosions occurring in the extremely distant universe. Some supernovae—like superluminous supernovae and pair-instability supernovae—are known for their extraordinary brightness. With ULTIMATE, we hope to discover these explosive phenomena from an era just a few hundred million years after the birth of the universe. Among the supernovae detected, we may find the explosions of so-called first stars, providing vital clues about the properties and evolution of the earliest stars and the origins of heavy elements in the universe.

ULTIMATE’s wide-field and high-resolution near-infrared observational capabilities are particularly powerful when observing densely packed or heavily dust-enshrouded regions—such as the Galactic center, the galactic plane, or star-forming regions within the Milky Way. Wide-field monitoring of the Galactic bulge is expected to detect stellar-mass black holes using the “microlensing” method, and long-term astrometric data will allow detailed studies of stellar motions. By conducting large-scale surveys along the galactic plane, ULTIMATE will be able to resolve individual stars in densely populated regions that were previously unresolvable, leading to significant advances in the study of various stellar types such as main-sequence stars, cataclysmic variables, supernova remnants, and OH/IR stars. Furthermore, systematic observations of star-forming regions across the Galaxy will allow for comprehensive studies of the initial mass function (IMF) under a variety of environmental conditions, revealing both its universality and its environmental dependence. In this way, ULTIMATE will pave the way for a new era across all fields of research where wide-field, high-resolution infrared observation is the key.