Time is running out to catch a giant planet's strange orbit

A team of researchers, including those from the University of Tokyo, discovered a rare type of planet, TOI-1355 b, that orbits its star in an unusual way. The planet is a hot Jupiter, meaning it is similar in size to Jupiter but orbits very close to its host star, which is much hotter than the sun. The planet's orbit is highly eccentric, meaning it is elliptical, and it completes an orbit in about two Earth days. The discovery is published in the journal Publications of the Astronomical Society of Japan. The unusual orbit could provide a rare opportunity to study this class of planet and how such planets move and evolve. However, the planet's evolving orbit means it won't be possible to observe it after about 2033.

The research team found that the planet's orbit is highly eccentric, and when they analyzed the brightness changes of the star, they noticed 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 the team began to research this planet in detail. The team used NASA's Transiting Exoplanet Survey Satellite (TESS) to measure the planetary mass and orbital eccentricity 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. The biggest challenge so far has been to measure the planetary mass from the brightness change in the TESS data. The team had to derive more complex model equations due to its elliptical orbit. They are preparing another paper about their investigation into how much the planetary orbit is inclined relative to the stellar rotation. They are also planning a proposal for an observation using NASA's James Webb Space Telescope.

• TOI-1355 b orbits its star, TOI-1355, in an elliptical path, completing an orbit in about two Earth days.
• The star is much hotter than the sun, at 8,400°C (15,100°F), compared with 5,500°C (9,900°F) at the surface of our sun.
• The planet's orbit is highly eccentric, and the team used TESS to measure its mass and orbital eccentricity.
• The discovery supports a theory that hot Jupiters around hot stars can have dramatic histories involving dynamic migration.
• The team is preparing another paper about how much the planetary orbit is inclined relative to the stellar rotation.
• They are planning a proposal for an observation using NASA's James Webb Space Telescope.

AI-generated summary of the original article — see the source for the full story.