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Japanese astronomers spot tiny Kuiper belt object with amateur telescopes

A commercial telescope is used to observe fixed stars in the Okinawa Prefecture city of Miyakojima on July 1, 2017, in this photo provided by Ko Arimatsu.

TOKYO -- A Japanese team of astronomers has discovered a distant, tiny object using amateur telescopes, establishing a low-cost approach for cutting-edge research into profound questions such as how our solar system was born.

The researchers from the National Astronomical Observatory and other institutions spotted the object with a radius of a mere 1.3 kilometers at a distance of about 5 billion kilometers from Earth near the outer edge of the solar system.

The astronomers say that the project cost just 3.5 million yen or so, including two telescopes with a price tag of about 1 million yen apiece -- about one-three-hundredth that of a similar international project. "We got top-notch results thanks largely to our ideas. Even little guys can beat giants," said a team member. The results of their observation were published Jan. 28 in British scientific journal Nature Astronomy.

The object is one of the so-called "Kuiper belt objects" (KBOs), which can be found beyond the orbit of Neptune, the outermost planet of our solar system at a distance of about 4.5 billion kilometers from the sun. Some of KBOs are relatively large like Pluto but many are very dim. Objects with a radius of around 1 to 10 kilometers had previously never been observed even by using huge telescopes.

Smaller objects are thought to have the same composition as the building blocks of planets, including Earth, in our solar system that was born 4.6 billion years ago. By studying the orbit and density of KBOs, astronomers can get closer to solving the mysteries behind the formation of the system.

In their research project, the Japanese astronomers installed the two telescopes each with a diameter of 28 centimeters on Miyako Island in the southernmost prefecture of Okinawa. They monitored approximately 2,000 shining fixed stars for a total of 60 hours, and found one dimmed for just 0.2 seconds -- because of a small object passing in front of the star. The team's analysis showed that the object was about 5 billion kilometers from Earth. The discovery was equivalent of spotting a 0.013-millimeter item from a distance of 50 kilometers.

Ko Arimatsu, a Kyoto University Astronomical Observatory researcher who played a leading role in the project, said, "The new (observation) method can broaden research projects by making them easier to join for amateurs and others."

(Japanese original by Mirai Nagira, Science & Environment News Department)

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