「重力波」初観測 宇宙への新しい窓が開いた

The Yomiuri Shimbun
1st detection of gravitational waves opens new window to universe
「重力波」初観測 宇宙への新しい窓が開いた

It is highly significant that a new observation method has been acquired to unravel the mysteries of the universe.

A research team that includes the California Institute of Technology has announced it detected gravitational waves from the universe.

Albert Einstein hypothesized the existence of gravitational waves a century ago based on his theory of general relativity.

According to Einstein’s theory, celestial bodies like black holes, which have a huge mass, would warp space-time around them. If such bodies collided, the warp would spread like ripples.

The research team believes the gravitational waves it detected were generated 1.3 billion light years from Earth when two black holes merged.

Celestial bodies with a large mass could not be observed directly by the electromagnetic waves — such as light, radio waves and X-rays — that have been conventionally used in astronomy.

The mass and internal conditions of stars can be inferred by observing gravitational waves. The findings may lead to elucidating such mysteries as how black holes whose nature has not been fully understood are created and how they inflate.

Gravitational waves are said to have been generated in the huge expansion of space that occurred right after the Big Bang, which created the cosmos, and the same ripples are said to still exist in space even today. The detection of such ripples may become reality.

Hopes for KAGRA project

The U.S. team’s landmark discovery has been supported by high-precision observation equipment.

The coherence of laser beams was used to measure the warps. Laser beams were sent through two pipes, each measuring four kilometers long, to detect warps of space-time caused by gravitational waves.

The measured warps were only one-ten quadrillionth of a millimeter. Vibration control equipment was installed to prevent the observation from being affected by vibrations caused by wind, sea waves and road traffic. The team has reportedly looked into all other possibilities to confirm that the observed data represented gravitational waves.

Similar observations have been attempted in Japan and Europe. A gravitational wave telescope named KAGRA, now under construction at the site of a mine in Hida, Gifu Prefecure, will start test operations this spring.

Leading the KAGRA project is Takaaki Kajita, a 2015 Nobel Prize laureate in Physics and the director of the Institute for Cosmic Ray Research at the University of Tokyo. Kajita expressed willingness to join international efforts in space observation, saying, “With the participation of KAGRA, the accuracy of observations will improve.”

The U.S. team was able to obtain its results soon after it started observations. Expectations are mounting regarding what discoveries KAGRA will make.

Japan has a long tradition in the field of astrophysics, and has contributed to the observation of neutrinos, thereby developing the science of astronomy.

We also want to see next-generation researchers mature in the field of gravitational wave astronomy.

(From The Yomiuri Shimbun, Feb. 13, 2016)

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