This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: A team of researchers, including those from the University of Tokyo, spotted a rare kind of planet that's unusually hot and eccentric. TOI-1355 b orbits its star, TOI-1355, which is also much hotter than our sun, in a strange way and incredibly quickly, completing an orbit in about two Earth days.
The work is published in the journal Publications of the Astronomical Society of Japan. This unusual orbit could provide a rare opportunity to study this class of planet and how such planets move and evolve. But the planet's evolving orbit means it won't be possible to observe it after about 2033.
Project Researcher Noriharu Watanabe and Professor Norio Narita from the Graduate School of Arts and Sciences at the University of Tokyo and their international team explore exoplanets and are especially interested in those unlike anything we find in our own solar system. They've recently discovered TOI-1355 b, a so-called hot Jupiter, which, as the name of the class suggests, is a Jupiter-like planet that orbits very close to its host star. In this case, the star is much hotter than our own, at 8,400°C (15,100°F), compared with 5,500°C (9,900°F) at the surface of our sun.
TOI-1355 b also orbits in a peculiar elliptical way that has enticed the team. "Planet surveys around stars as hot as or cooler than the sun are flourishing, and thousands of planets have been discovered around such stars. But planet surveys around hotter stars are still not advanced," said Watanabe.
"In this project, we hunted for planets around hot stars to examine the diversity of exoplanets more broadly. "When we investigated the change in brightness of TOI-1355 from prior data, we found that the secondary eclipse, a phenomenon in which a planet passes behind a star, occurred earlier than the timing assumed for a circular orbit. This was unusual for hot Jupiters around hot stars, and this is why we began to research this planet in detail." NASA's Transiting Exoplanet Survey Satellite (TESS) space telescope recently found periodic dimming of the star TOI-1355, and Narita's team determined this was due to a planetary transit.
They measured the planetary mass and orbital eccentricity — the degree of deviation from a circular orbit — from changes in stellar and planetary brightness observed by TESS. The discovery of a hot Jupiter with a highly eccentric orbit is important because it supports a theory that hot Jupiters around hot stars can have dramatic histories involving dynamic migration, perhaps due to planets interacting through gravity and altering each other's orbits. This kind of interaction is predicted to cause a high eccentricity that will later become more circular with time.
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