subaru telescope
This optical and infrared instrument has been operating since before the turn of the century, and it continues to provide valuable astronomical observations
Get inside one of the most impressive optical and infrared scopes that sits on a volcano
Sitting on top of the dormant volcano Mauna Kea in Hawaii, the Subaru Telescope takes advantage of one of the best astronomical observation sites on the planet. When the National Astronomical Observatory of Japan (NAOJ) commissioned the telescope back in 1991, they set out to build the best optical and infrared telescope possible, capable of discovering the secrets of the cosmos.
Although ‘Subaru’ may be a name commonly associated with automobiles, it originates from the Japanese name for the young cluster we know as Pleiades (Messier 45). Not only is it another name for ‘The Seven Sisters’ in the constellation of Taurus, but it also translates to ‘tie together’ from Japanese. This seems like a very befitting name for one of the world’s most innovative telescopes, uniting the international astronomical community in their search for answers.
Construction began at the Mauna Kea site in June 1992 and wasn’t fully completed until December 1998, starting scientific observations in January 1999. Some of the first light observations include the Orion Nebula (Messier 42), the spiral galaxy NGC 4051 and Abell 851. The construction process was a long and arduous journey. Engineers and scientists wanted to create the thinnest primary mirror possible, combine it with the latest technological advancements and enclose it in a state-of-the-art protective cylindrical dome, which helps to minimise air turbulence within the telescope's enclosure.
The product of such hard work and determination has brought us the sixth-largest optical reflector telescope, which is fitted with an impressive 8.2-metre (26.9-foot) single primary mirror within a Ritchey-Chrétien optics system.
The mirror was carefully designed to provide the highest possible resolving power. This attention to detail results in an average surface error of just 0.012 micrometres - equivalent to about one in five thousandths of the thickness of a human hair.
There are four focal points to the Subaru Telescope. Each of these focal points has carefullyselected designated cameras and spectrographs to allow for the observation of the greatest range of cosmic events. The prime focus is situated at the tip of the telescope’s ‘nose’, and this region has an impressive 870-megapixel, optical camera as well as a wide-field spectroscopy sytem able to image over 100 objects at once. Lower down towards the base
there are two Nasmyth foci on opposite ends of the telescope; one collects optical light and the other infrared. Underneath the telescope is the Cassegrain focus; this can have different instruments attached depending on the research goals. The three Cassegrain instruments – the Faint Object Camera and Spectrograph (FOCAS), the Multi-Object Infrared Camera and Spectrograph (MOIRCS) and the Cooled Mid-Infrared Camera and Spectrograph (COMICS). While the Sun is out, astronomers must plan which target they intend to observe and then determine which instruments are to be used. This is when engineers use the Cassegrain Instrument Automatic Exchanger (CIAX) to swap over these hefty pieces of Cassegrain apparatus in roughly two hours. The Top Unit Exchanger helps in the exchange of the secondary mirrors and the Hyper Suprime-Cam (HSC). The HSC replaced the original Subaru Prime Focus Camera (Suprime-Cam) in 2012, and consists of 116 highly sensitive CCDs to provide a field of view, which is seven-times wider than Suprime-Cam.
Subaru’s uniqueness and collaborations with other worldwide organisations has meant the telescope has been at the heart of scientific discoveries for around 19 years. NAOJ was also involved in the follow-up observations of two merging neutron stars, which created the gravitational wave emission formally known as GW170817.
The Subaru Telescope was one of the many telescopes that turned its top-tier optics to the constellation of Hydra to find the visible counterpart of the gravitational wave detection. This is only one example of the groundbreaking discoveries that
Subaru has made or contributed to throughout the years. Subaru has not just focused on the depths of the universe though; it has also provided us with valuable images of objects within our Solar System. For example, Subaru's mid-infrared imaging, using COMICS, was used to aid NASA’s Juno spacecraft, providing information about the temperature distribution of Jupiter.
NAOJ continues to maintain and improve the telescope to an incredibly high standard, establishing itself as one of the world’s best groundbased optical telescopes. Not only does it have the finest optics, technologies and engineers dedicated to its maintenance, but its prime location on the Mauna Kea volcano provides astronomers with
240 clear nights per year. It's thanks to this why the Subaru Telescope has been, and remains to be, pivotal in the role of understanding the universe.