This article was written by the Southern Iwate Regional Development Bureau, and translated by Amanda Wayama.

In April 2019, humankind took its first photograph of a black hole. One of the facilities that greatly contributed to that project was the National Astronomical Observatory of Japan in Mizusawa, a district in Oshu City, Iwate Prefecture.

In this issue, the researchers at NAOJ Mizusawa have helped us out to put together an article on the 120 years of history and achievements of the facility since its founding, as well as the various projects it’s working on currently.

NAOJ Mizusawa over the 120 years since its founding

By Ishikawa Toshiaki, Research Engineer at the Mizusawa VLBI Observatory, NAOJ

Last year marked the 120^th anniversary of the founding of the Mizusawa Temporary International Latitude Station, the original facility built in 1899 that eventually went on to become the Mizusawa VLBI Observatory at NAOJ.

In the latter half of the 19^th century, researchers in the United States figured out from their astronomical observations that the Earth tended to wobble on its axis (a term called “latitude variation”). In order to solve the mystery, the International Association of Geodesy (IAG) decided to take measurements from 6 different places at the latitude of 39 degrees and 8 minutes north. As one of the candidate sites, Japan received a request from IAG to build an observatory in the country, and the Japanese government made the extraordinary decision to construct the International Latitude Station in Mizusawa. It was initially only supposed to be a temporary project ending in five years’ time, but Kimura Hisashi (the first director of the facility) discovered that there was an unknown variable in the earth’s latitude variation, which he called the z-term. This discovery led to a change in the world’s view of Japan, and the next challenge was to figure out why the z-term existed. That research continued for more than 80 years.

Once the reasons for the z-term were understood, the International Latitude Ovservatory of Mizusawa(ILOM) branched out into new fields of research. After it was reorganized into National Astronomical Observatory of Japan(NAOJ) Mizusawa, the facility worked on many things, such as creating detailed maps of the galaxy with the VERA array, and developing instruments of the Kaguya lunar probe as well as observations and scientific research. Observatory director Honma and other researchers are part of the Japanese team of the Event Horizon Telescope (EHT) project, which last year announced the first successful photograph of a black hole.

As a pioneer of astronomy and other related subjects, the NAOJ Mizusawa facility will continue to carry out research here, in this region selected by famous physicist Tanakadate Aikitsu and Kimura Hisashi.

Chronology of NAOJ Mizusawa

1899 ― Establishment of the Mizusawa Temporary International Latitude Station , and observations begin for the International Latitude Observation Service (ILS)

1902 ― Discovery of the z-term by Kimura Hisashi

1920 ― Mizusawa Station was reorganized into a permanent observatory

1922 -1935 ― Central Bureau of the ILS at Mizusawa

1962-1987 ―Central Bureau of the International Polar Motion Service (IPMS) at Mizusawa

1970 ― The reasons for the z-term are understood (Wako Yasujiro)

1971 ― The International Astronomical Union (IAU) sysmposium No.48 “Rotation of the Earth” was held in Morioka City

1980 ― ILOM releases results of the International Latitude Service in a Homogeneous System

1988 ― The ILOM was reorganized into National Astronomical Observatory of Japan (NAOJ) Mizusawa

1992 ― Construction of a 10m radio telescope is completed, and domestic observations for the VLBI network begin

2001-2002 ― The VERA array is completed

2007-2009 ― VLBI observations of the Kaguya (SELENE) lunar probe

2013 ― The supercomputer ATERUI is installed

2018 ― The supercomputer ATERUI II is installed

2019 ― Successful touchdowns of the Hayabusa2 spacecraft onto the asteroid Ryugu

2019 ― Release of the image of the M87 giant black hole by the Event Horizon Telescope (EHT)

The environs at NAOJ Mizusawa. Here is the VERA 20m antenna, and you can also see the former zenith telescope room from 1899 at the 39°8′mark（Credit: NAOJ）

Kimura Hisashi (left) and Tanakatadate Aikitsu (right)（Credit: NAOJ）

VERA（VLBI Exploration of Radio Astrometry）

By Professor Honma Mareki, Director of the Mizusawa VLBI Observatory, NAOJ

The Mizusawa VLBI (Very Long Baseline Interferometry) Observatory of NAOJ operates the VERA (VLBI Exploration of Radio Astrometry) array consisting of four radio observatories, which also includes ones in Satsuma-Sendai City (Kagoshima Pref), Ogasawara Village (Tokyo), and Ishigaki City (Okinawa Pref) in addition to the one in Ohshu. Construction began in 2000, and these facilities have been continuously operated since 2002 when they were completed. In the first picture below, you can see the 20m radio telescope and night sky at the Mizusawa VLBI Observatory.

The VERA array observes maser objects (mostly places where young stars are formed) within the Milky Way Galaxy. VERA makes observations day and night, because by measuring distance and movement over more than a year’s time, we can figure out the size of the galaxy, the speed of its movement, and the distribution of dark matter within the Milky Way. VERA has already recorded the distance and movement of more than 100 celestial objects, and with results from US and European telescopes, we can clearly see the distribution of maser objects and their movement within the Milky Way (picture 2). Through this, we can obtain a basic scale of the Milky Way, such as the distance to its center and the speed of its rotation. Research is on-going to reveal the distribution of dark matter and the structure of the Milky Way’s spiral arms.

Picture 1: The 20m radio telescope (right) at NAOJ Mizusawa VLBI observatory, as well as the movements of the northern stars (Credit: NAOJ, Photo taken by: Iijima Yutaka)

Picture 2: With VERA’s observations, the distribution of maser objects and their movements become clear (point and arrows). The spiral arms in the background are a conceptual drawing.（Credit: NAOJ）

RISE Project

By Assistant Professor Noda Hirotomo, RISE Project, NAOJ

Our project has inherited Mizusawa’s tradition of geodesy with its research into the solar system’s planets, asteroids, moons, and more.

10 years ago, in the Kaguya Lunar Exploration Program, we developed and operated scientific instruments that measured the lunar gravity field and terrain. The name for the RISE project at that time was taken from the term Research in Selenodesy (measuring the shape, orientation and gravity field of the moon), but after the Kaguya project, we expanded our research field to the celestial bodies within the solar system, and the term now stands for Research of Interior Structure and Evolution of solar system bodies – a keyword for our work.

For around one and a half years from 2018 to 2019, the Japanese spacecraft Hayabusa2 explored the asteroid Ryugu, and we fulfilled a central role in developing and operating a laser altimeter aboard, one of four scientific instruments on the probe.

We have ended mapping on the asteroid, and now scientific research will take center stage. We are working on projects that aim to solve the mysteries of the universe’s celestial bodies, like the Japanese MMX (Martian Moons eXploration) project that works to survey the moons of Mars, and the European JUICE (Jupiter Icy moons Explorer) project that works to survey the icy satellites of Jupiter.

Project Director Namiki wants to learn about the moon so bad that he’s trying to cut it clean in half (Credit: NAOJ）

ATERUI Ⅱ

By Dr. Fukushi Hinako, Senior Specialist at the Center for Computational Astrophysics, NAOJ

Currently in the field of astronomy, along with observations and theoretical studies, astronomical simulations are our most crucial tools – calculations based on the laws of physics to create experiments of celestial phenomena within computers.

NAOJ Mizusawa has a supercomputer dedicated to astronomical simulations, “ATERUI II”. It’s capable of three quadrillion calculations per second, the world’s fastest supercomputer for astrophysical simulations. Astrophysicists at home and abroad access this computer for conducting simulations of various astronomical phenomena. ATERUI II can make large-scale calculations about how, for example, the structure of the Universe evolved in the 13.8 billion years since its beginnings. In addition, ATERUI II contributed to research for the imaging of the black hole by simulating and predicting how light would travel around it.

The word “Aterui” is the name of a hero of the Mizusawa area who lived around 1,200 years ago. We named this supercomputer ATERUI hoping that it would bravely challenge to solve the mysteries of the Universe. It has been 120 years since Kimura Hisashi made his calculations using an abacus, and now in that same Mizusawa area, ATERUI II updates our understandings of the Universe by simulations.

ATERUI II (Credit: NAOJ）

A simulation of the large-scale structure of the universe (Credit: Ishiyama Tomoaki/Chiba University）

EHT（Event Horizon Telescope Collaboration）

By Dr. Tazaki Fumie, Specially Appointed Research Staff at Mizusawa VLBI Observatory, NAOJ

In April 2019, news spread around the world that humankind had taken its very first picture of a black hole. Ever since Einstein proposed the theory of general relativity, we had theorized the existence of black holes, which are bodies with gravitational fields strong enough to swallow even light. However, with this photo, we had finally got irretrievable proof of the shadow of the black hole (the black portion of the picture). Now that scientists have taken the first photo in human history of a black hole, the curtain has opened on a new era of black hole research.

The picture is of a giant black hole at the center of an elliptical galaxy within the Virgo constellation called M87. The Event Horizon Telescope (EHT) that took the picture is the combination of 8 radio telescopes in 6 places across the world, forming a telescope the size of the globe. This achieves an excellent resolution to take a picture of the black hole very far away, whose apparent size is same as a tennis ball on the moon. Over 200 researchers from around the world worked together for over ten years to achieve this. There were thirteen from Japan who were involved with the projects, and five of us were at Mizusawa. We were involved with developing and operating observation devices, and creating images from the observation data.

We understand that there is a current of plasma flowing from the giant black hole in M87, called a jet. A telescope that’s particularly suited for researching this jet would be the EAVN (East Asian VLBI Network). By combining radio telescopes in Japan, South Korea, and China, we can form a giant radio telescope the size of East Asia. The 20m radio telescope in Mizusawa is one of those telescopes. At Mizusawa VLBI Observatory, we will use the technological prowess and research power available through joining up with the telescopes around the world, and continue to research black holes with the EHT and EAVN.

Photo 1: The photo of the M87 giant black hole taken by the EHT（Credit: Event Horizon Telescope Collaboration)

Photo 2: The Mizusawa members of EHT. Taken in front of the 20m radio telescope at the observatory（Credit: NAOJ）

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How did you like this article?

Should the ILC be realized, it will be able to work with NAOJ Mizusawa along with the Oshu Space & Astronomy Museum (site of the former Mizusawa Latitude Observatory), and we think it will become a hub for scientific research and exchange in the region. We’re really looking forward to it.

We want to give a big thanks to the folks at NAOJ Mizusawa for their cooperation. Best wishes for your continued success!