For more than a quarter century, workers have toiled atop a mountain in Chile to help researchers explore the universe for the origins of life.
They have finally completed the Atacama Observatory at the University of Tokyo, awaiting only the installation of an infrared telescope using a mirror more than 6 meters in diameter.
The observatory, known as TAO, is located atop the 5,640-meter-high Mount Chajnantor in the arid Atacama Desert, the driest region on Earth.
About 200 officials from the university, the Japanese Ministry of Education and the Chilean government attended a ceremony marking the completion of the work in Santiago in late April.
Julio Bravo Yubini, a senior official at the Chilean Foreign Ministry, said in his speech that he hoped the TAO telescope, one of the world’s best infrared instruments, would make breakthroughs in exploring the universe.
The project began in 1998 with the construction of a temporary road to transport construction materials to the summit. At these rarefied heights, there is about half as much oxygen as at ground level, making construction work extremely arduous.
About 350 workers, including 120 Japanese, were involved.
“All the workers carried oxygen tanks on their backs to avoid altitude sickness,” recalls Takashi Miyata, director of TAO, which specializes in infrared astronomy.
In winter, temperatures drop and snow does not melt as easily as at lower altitudes.
Despite the inhospitable environment, the project progressed and workers installed a one-meter-diameter telescope in 2009, earning it recognition from Guinness World Records as the world’s tallest astronomical observatory.
However, the TAO project had to overcome other obstacles.
“We had to fight against social unrest in Chile and the coronavirus pandemic,” Miyata said.
The observation and operations building is now complete, as is a facility that will house a telescope with a 6.5-meter diameter primary mirror. Installation of the instrument is scheduled for this fall at the earliest.
The University of Tokyo has chosen Chile, a country in the southern hemisphere, as the site of its outpost.
The National Astronomical Observatory of Japan operates the 8.2-meter Subaru Infrared Optical Telescope in Hawaii. Japanese scientists will now be able to observe the universe with telescopes in opposite hemispheres.
Scientists at the university chose Mount Chajnantor over other candidate sites in the southern hemisphere because the atmosphere around the mountain’s summit is thin and the mountain is located in arid conditions.
Only a small fraction of the universe’s infrared radiation reaches the Earth’s surface after a large percentage is absorbed by water vapor in the atmosphere.
According to the University of Tokyo, the Subaru telescope, located at an altitude of 4,200 meters, captures only 5 percent of the mid-infrared, with a wavelength of 31.5 micrometers.
That figure has fallen almost to zero for the European Southern Observatory’s Very Large Telescope (VLT), located at an altitude of 2,600 metres on Cerro Paranal in the Atacama Desert.
But the TAO can detect 40 percent of mid-infrared light in that range.
As for near-infrared light, whose wavelength is shorter than mid-infrared, the TAO telescope can observe the spectral region transparently and with high sensitivity.
Covering a wider field of view, the telescope should perform admirably when comprehensively surveying a region of the sky.
“We chose a dry region with less water vapor, based on data collected by weather satellites and other sources,” said Yuzuru Yoshii, professor emeritus of cosmic physics at the University of Tokyo, who has led the TAO project for the past 26 years.
“The telescope will be installed at a higher altitude than any other observatory in the world, the best possible setting that will allow the infrared telescope to demonstrate its maximum capabilities.”
EXPANDING KNOWLEDGE OF THE UNIVERSE
On the plateau of the Atacama Desert is the Atacama Large Millimeter/Submillimeter Array, known as ALMA, the result of the work of an international consortium of research institutions, including those from Japan, the United States and EU countries.
The ALMA transformative radio telescope can study cosmic light at the boundary between radio waves and infrared light.
Scientists at the University of Tokyo hope that combining observations of the same region of space by ALMA and TAO will deepen their understanding of the universe.
The TAO will be fully operational in 2025.
The TAO telescope is not among the top 10 infrared telescopes in the world in terms of primary mirror diameter.
But its infrared capabilities are unmatched, matching those of space telescopes.
It also has an advantage over space-based instruments in that a ground-based telescope can remain operational for decades with upgrades.
NASA’s James Webb Space Telescope has a lifespan of about 10 years in orbit.
The main goal of the TAO project is to uncover two enduring mysteries: the origins of the universe and galaxies and the origins of planets.
By capturing the object in the mid-infrared, scientists can observe celestial bodies and substances at low temperatures. They will try to understand the process of planet birth by studying the dust that surrounds stars.
Scientists may be able to gain clues about how galaxies formed by making near-infrared observations with high sensitivity and a wider field of view.
The observatory operated by the University of Tokyo provides opportunities for its own researchers to collect data on specific astronomical objects over an extended period of time.
They can explore the evolution of the universe through precise observation of supermassive black holes located light-years away and the nature of dark energy shrouded in mystery.
“We believe that if we measure the precise distances between astronomical objects, it will give us a more complete picture of the structure and expansion of the universe,” Miyata said.
TAO scientists will have 42 to 47 percent of the telescope’s observing time.
Japanese researchers will be allocated 33 to 38 percent of the telescope’s remaining observing time.
Young researchers, including graduate students, will have access to a certain percentage of this time, an initiative aimed at developing a new generation of astronomers.
Chilean scientists will be granted 10 percent of the observing time, while astronomers in and outside Japan will be able to access the telescope for 5 to 15 percent of the observing time for a fee.
With the project largely complete, Yoshii said he feels rewarded for persevering despite the many challenges he and his colleagues had to overcome.
“Some have criticized the project as reckless, while others have questioned its necessity,” he said. “We are glad we never gave up. But completing the observatory is not the goal, but only the starting point.”
The world’s leading infrared telescopes
(Name, country of operation, location, size of primary mirrors)
The Very Large Telescope (VLT), EU, Chile, four units of 8.1 meters each
Keck Telescope, USA, Hawaii, two 10-meter units each
The Large Binocular Telescope (LBT), the United States and other countries, Arizona, two 8.3-meter objectives each
The Great Canary Islands Telescope, Spain and other countries, Canary Islands in Spain, 10.4 meters
The Large South African Telescope, South Africa and other countries, South Africa, 9.2 meters
The Hobby-Eberly Telescope, USA, Texas, 9.2 meters
Subaru Telescope, Japan, Hawaii, 8.2 meters
Tokyo University Atacama Observatory (TAO), Japan, Chile, 6.5 meters
(Source: National Astronomical Observatory of Japan data for 2024)