International research team KELT has discovered the hottest extrasolar planet in observation history, with daytime temperatures as high as 4,300 degrees Celsius. KELT is a network research team of researchers from Japan and Europe in addition to the United States, and is observing with two very small telescopes with a diameter of only 4.2 cm.From Japan, Assistant Professor Kenho Narita of the Department of Astronomy, Graduate School of Science, The University of Tokyo and Akihiko Fukui, Specially Appointed Specialist of the Okayama Astronomical Observatory of the National Astronomical Observatory of Japan, are participating.

 In recent searches for extrasolar planets, attention has been focused on stars (stars that shine like the sun) at temperatures lower than the sun (about 6.000 degrees) (2,300 to 3,500 degrees).On the other hand, in order to understand the whole picture of planet formation in the universe, it is also important to search for planets around hot stars.More than 100 planets called "Hot Jupiter" have been discovered in the Sun-type stars, where giant gas giants like Jupiter revolve near the main star.On the other hand, for stars above 7,000 degrees Celsius, which are hotter than solar-type stars, only six Hot Jupiters have been discovered even now, more than 20 years after the discovery of the first extrasolar planet.

The planet discovered this time is named KELT-9b and revolves around the star KELT-10,000 at about 9 degrees Celsius in a short cycle of about 1.5 days.Since it revolves in the immediate vicinity of a very hot star, the temperature of the atmosphere of this planet is comparable to that of the star, even though it is a planet that does not shine by itself.

This planet receives strong ultraviolet rays from the main star, and the atmosphere may be flowing out like a comet.However, it is expected that detailed observations of the planetary atmosphere in the future will reveal the fate of the planet, such as whether all the atmosphere will be stripped from the planet or whether it will be swallowed by the main star as Hot Jupiter before that. There is.

Paper information:[Nature] A giant planet undergoing extreme ultraviolet irradiation by its hot massive-star host

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