New tool helps Subaru researchers better understand formation, evolution of universe

Researchers at Subaru Telescope atop Mauna Kea have a new first-of-its-kind tool to help them study everything in the cosmos from nearby objects to the most distant in the universe.

Called the Prime Focus Spectrograph, it features about 2,400 prisms scattered across the extremely wide field of view available at the Subaru Telescope’s primary focus, allowing for simultaneous spectroscopic observation and dramatically enhancing its efficiency.

The unrivaled capability the new spectrograph provides will allow astronomers to precisely understand how galaxies — and the universe itself — formed and evolved.

“The discoveries that will be made with this cutting-edge instrument are something all of the people of Hawai’i can be proud of,” said Naoyuki Tamura, professor and project manager of Prime Focus Spectrograph at Subaru Telescope. “To be at the center of such a meaningful international collaboration and human endeavor.”

It’s a powerful compound eye that — just like an insect’s — allows the telescope to simultaneously observe a massively wide field. In fact, this eye let’s Subaru see thousands of celestial objects at once.

The innovate instrument, made possible through a large international collaboration, is even more powerful than a bug’s eye. It can capture cosmic rainbows called spectra, enabling even more detailed exploration of the universe.

Subaru’s ultrawide field of view and world-renowned large light-gathering power allows the spectrograph to position each of its fibers to collect light and obtain spectra across the entire visible light range and part of the near-infrared band.

Each fiber, or facet, focuses in a different direction to cover a wide area while perceiving the colors of light from that direction.

The Prime Focus Spectrograph is the result of nearly 15 years of work and support from global industrial partners.

Its development was led by an international collaboration of 20-plus research institutions in Japan, the United States, France, Brazil, Taiwan, Germany and China, including scientists, engineers and technicians based in Hawaiʻi.

Subaru Telescope at the National Astronomical Observatory of Japan played a central role in the spectrograph’s development and overseeing coordination of the project while also being responsible for and operating the instrument.

Many Prime Focus Spectrograph parts and modules developed and assembled in various countries were also gathered on Mauna Kea and installed on the Subaru Telescope.

The international team has conducted engineering tests and observations with the Subaru Telescope since 2021 and will soon start scientific operations.

A large-sky survey program is planned during the next 5 years or so, throughout a total of 360 nights. This survey will take spectra of millions of distant galaxies, as well as hundreds of thousands of stars in the Milky Way and our neighboring Andromeda Galaxy.

Subaru is the most competitive among 8-meter telescopes around the globe, with the largest survey capability in the world, and the new spectrograph is now one of the flagship instruments of the Subaru Telescope 2.0 era.