IEEE Honors Japanese Radio Astronomy Telescope That Discovered a Black Hole

The device was the largest of its kind when it was built

29 June 2017

In 1982 engineers in Tokyo finished building a millimeter-wave telescope that would give scientists a better look at interstellar phenomena. With a surface aperture of 45-meters in diameter, it was the largest of its kind at the time and arose from a partnership between the Tokyo Astronomical Observatory and Mitsubishi Electric Corp. The telescope has led to several discoveries about the universe that advanced the field of radio astronomy.

This month the telescope at the Nobeyama Radio Observatory, in Nagano, has been named an IEEE Milestone. Administered by the IEEE History Center and supported by donors, the milestone program recognizes outstanding technical developments around the world.


The Nobeyama telescope collects weak signals from distant objects in space in the millimeter range (1 mm to 10 mm). To ensure the radio-signal reflector panel on the surface of the telescope would maintain its shape and not deform because of temperature variations in its surroundings, the designers installed fans inside the back structure—basically the spine of the telescope’s dish that anchors it to the ground. They also installed aluminum honeycomb sandwich panels with carbon fiber–reinforced plastic to resist gravitational pull and possible deformation when the telescope is tilted at different angles. This allows the telescope and its antenna to collect radio waves regardless of the direction in which it is pointed.

The telescope has helped scientists study interstellar matter and identify new molecules in the universe. It also detected high-velocity water vapor emitted from the center of a distant galaxy—providing strong evidence of the existence of a black hole there. The instrument has helped observe light emissions from molecules, masers, and plasmas.

The Nobeyama remained the largest single-aperture millimeter-wave telescope in the world for almost 25 years until eclipsed by the Large Millimeter Telescope Alfonso Serrano. In Ciudad Serdán, Mexico, that 50-m-diameter radio telescope was put into service in 2006.


The Nobeyama telescope was honored on 14 June at the Nobeyama Radio Observatory. A plaque mounted in the exhibition room reads:

In 1982, the Tokyo Astronomical Observatory in collaboration with Mitsubishi Electric Corporation completed the 45-m telescope as the world’s largest antenna for millimeter-wave radio astronomy. The 45-m telescope’s innovative engineering contributed to the progress of radio astronomy by enabling high-resolution and high-sensitivity observations. Notable discoveries included new interstellar molecules and a black hole.

This article was written with assistance from the IEEE History Center, which is partially funded by donations to the IEEE Foundation.

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