Subaru Telescope’s new compound eye to start exploring the universe in February

The Subaru Telescope in Hawaiʻi, announced the addition of a new capability as it studies from nearby objects to the distant Universe. A powerful compound eye likened to that of an insect will allow the telescope to simultaneously observe about 2,400 celestial bodies. This innovative eye can capture cosmic rainbows (spectra), enabling detailed exploration of the Universe.

The instrument, called the Prime Focus Spectrograph (PFS), features approximately 2,400 prisms scattered across the extremely wide field of view available at the Subaru Telescope’s primary focus, allowing for simultaneous spectroscopic observation of thousands of celestial objects.

Scientists say this unrivaled capability will help researchers precisely understand the formation and evolution of galaxies and the Universe.

PFS will be one of the flagship instruments of the “Subaru Telescope 2.0” era. Taking advantage of the Subaru Telescope’s ultra wide field of view, approximately 1.3 degrees in diameter at the prime focus, and large light-gathering power, PFS will position 2,400 fibers to collect light from celestial objects and simultaneously obtain spectra across the entire visible light range and part of the near-infrared band.

Just like the compound eyes of insects, each facet (fiber) focuses in a different direction to cover a wide area while perceiving the colors of light from that direction. This will dramatically enhance the Subaru Telescope’s spectroscopic observation efficiency.

As a result of work spanning nearly 15 years with support from industrial partners around the world, the development of PFS has been led by an international collaboration of over 20 research institutions in Japan, the US, France, Brazil, Taiwan, Germany and China, including Hawaiʻi-based scientists, engineers and technicians.

Notably, the University of Tokyo Kavli Institute for the Physics and Mathematics of the Universe has taken the lead in proposing and developing the instrument as well as planning large-sky survey observations, with the goal of testing various theoretical models about the formation of the Universe.

Subaru Telescope at the National Astronomical Observatory of Japan (NAOJ) has also played a central role, participating in the development of the instrument and overseeing the coordination of the project, while also being responsible for the acceptance and operation of the instrument.

Many PFS parts and modules developed and assembled in various countries were gathered on Maunakea and installed on the Subaru Telescope. Since 2021, the international team has conducted engineering tests and observations with the Subaru Telescope and will start scientific operations.

Naoyuki Tamura (Professor at Subaru Telescope at NAOJ), working in Hilo, Hawaiʻi, the PFS Project Manager who has led the instrumentation, said: “During the manufacturing, assembly, and testing processes, I have been just continuing efforts to bring people and teams together who are dispersed across different institutes. It is deeply moving to see it come together as a single instrument system. However, this is just a stepping stone towards ultimate goals such as continuing the operation for a long term, producing unprecedented scientific outputs, and sharing exciting news from Maunakea with the local community to the fullest. The discoveries that will be made with this cutting-edge instrument are something all of the people of Hawaiʻi can be proud of; to be at the center of such a meaningful international collaboration and human endeavor.”

The PFS team plans to carry out a large-sky survey program over the next five or so years, utilizing a total of 360 nights of telescope time. 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.