Photo/Illutration The first image of Sagittarius A*, a black hole at the center of the Milky Way ((c) EHT Collaboration)

Japanese astronomers are among an international research team that successfully captured the first image of a black hole at the center of the Milky Way, which could shed light on the formation of our galaxy.

The Event Horizon Telescope Collaboration, an international research team working to shoot images of a black hole, announced on May 12 that it successfully provided the first visual evidence of Sagittarius A*, a black hole about 27,000 light years from Earth.

The team comprises more than 300 scientists from the National Astronomical Observatory of Japan (NAOJ) and 12 other research institutions in the United States, Europe and elsewhere. About 20 Japanese astronomers are participating in the project, which started around 2006.

The latest achievement was the team’s second since April 2019, when it released the first image of a black hole from the Messier 87 galaxy, which is about 55 million light years from Earth.

The researchers used observational data on Sagittarius A* and the black hole called M87 collected in April 2017 from eight radio telescope observatories in Chile, Hawaii, Antarctica and three other locations across the globe. The combined array created a virtual telescope with an aperture of about 10,000 kilometers, close to the Earth’s diameter.

The NAOJ is involved in operating the ALMA Observatory in Chile, which plays a central role in the project.

It had been considered impossible to capture an image of a black hole because its strong gravity prevents light from escaping it. The team analyzed radio waves released from gas orbiting around the black holes to show the outlines of the holes.

In addition to image processing methods used to produce the image of M87, the team adopted four new methods, including those proposed by Japanese researchers, to capture the outline of Sagittarius A* because the team had difficulty analyzing the radio waves around it.

Sagittarius A* is located closer to Earth but smaller than M87, which is about 6.5 billion times as massive as the sun.

The researchers hope they can better understand a black hole by comparing data obtained from the two black holes, which each have different characteristics.

Their latest findings were published in the U.S. scientific journal Astrophysical Journal Letters. They were also posted on the team’s website: (https://eventhorizontelescope.org/blog/astronomers-reveal-first-image-black-hole-heart-our-galaxy).

(This article was written by Shoko Tamaki and Ryoma Komiyama.)

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