Artist’s impression of hot Jupiter-like planets. After around 2033, planet TOI-1355 b will disappear from view as it must pass between the star and Earth to be seen. There would be no major changes for the planet itself. But astronomers will become unable to observe its transits to characterize the planetary nature for hundreds of years.
Image Credit: © ESA/Hubble, N. Bartmann
(CC BY 4.0)
Scientific Frontline: Extended "At a Glance" Summary: TOI-1355 b
The Core Concept: TOI-1355 b is an unusually hot, Jupiter-like exoplanet with a highly eccentric (elliptical) orbit that brings it extremely close to its exceptionally hot host star.
Key Distinction/Mechanism: Unlike most "hot Jupiters" which tend to settle into circular orbits, TOI-1355 b maintains a highly eccentric path, completing an orbit in roughly two Earth days. This deviation allows researchers to observe dynamic planetary migration driven by gravitational interactions with other bodies and subsequent orbital shrinking due to the host star's tidal forces.
Origin/History: Observations were recently confirmed using NASA's Transiting Exoplanet Survey Satellite (TESS). Astronomers anticipate that due to the evolution of its orbit, TOI-1355 b will become unobservable via transit methods around the year 2033.
Major Frameworks/Components:
- Orbital Eccentricity: The planet's highly elliptical path deviates significantly from a circular orbit.
- Hot Jupiter Classification: Gas giants orbiting in extreme proximity to their host stars.
- Dynamic Migration: The theory that planets can undergo dramatic orbital shifts due to gravitational interference from other celestial bodies before circularizing over time.
- Tidal Effects: The host star exerts gravitational forces that gradually shrink the planet's orbit.
Branch of Science: Astronomy, Planetary Science.
Future Application: Further study of TOI-1355 b using the James Webb Space Telescope could refine models of how giant planets evolve, migrate, and interact in multi-body systems, especially around exceptionally hot early-A-type stars.
Why It Matters: This planet offers a rare, time-limited window to study the extreme evolutionary mechanics of planetary orbits before its transit geometry shifts entirely out of view.
A team of researchers, including scientists from the University of Tokyo, discovered a rare type of planet that is unusually hot and eccentric. The planet, TOI-1355 b, completes a rapid, highly atypical orbit around its host star, TOI-1355 (which is significantly hotter than our sun), in approximately two Earth days. This unusual orbit provides a rare opportunity to study this class of planets and their evolutionary dynamics. However, the planet's evolving orbit means it will not be observable after approximately 2033.
Project Researcher Noriharu Watanabe and Professor Norio Narita of the Graduate School of Arts and Sciences at the University of Tokyo, along with their international team, explore extrasolar planets, focusing on those unlike any found in our solar system. They recently discovered TOI-1355 b, a "hot Jupiter"—a massive, Jupiter-like planet that orbits in close proximity to its host star. In this system, the host star reaches a surface temperature of 8,400 degrees Celsius, which is substantially hotter than the 5,500 degrees Celsius surface of our sun. Furthermore, TOI-1355 b travels in a peculiarly elliptical orbit that has intrigued the research 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; however, planet surveys around hotter stars are still not advanced," Watanabe said. "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 its host star—occurred earlier than the timing assumed for a circular orbit. This was unusual for hot Jupiters around hot stars, and it is why we began to research this planet in detail."
NASA’s Transiting Exoplanet Survey Satellite (TESS) space telescope recently detected 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 amount of deviation from a circular orbit—from the change in stellar and planetary brightness observed by TESS. The discovery of a hot Jupiter with a highly eccentric orbit is important, as it supports the theory that hot Jupiters around hot stars undergo dynamic migration. This migration is perhaps due to planets interacting gravitationally and altering one another's orbits. This type of interaction is predicted to cause a high initial eccentricity that gradually circularizes over time.
"It is believed that the planetary orbit initially became highly elliptical due to gravitational interaction with other celestial bodies, such as other giant planets, and shrank gradually later due to the tidal effect of its host star," Watanabe said. "The biggest challenge so far has been measuring the planetary mass from the brightness changes in the TESS data. We had to derive more complex model equations due to the planet's elliptical orbit. We are preparing another paper detailing our investigation into the planetary orbit's inclination relative to stellar rotation, and we are also planning an observation proposal using NASA’s James Webb Space Telescope."
Published in journal: Publications of the Astronomical Society of Japan
Authors: Noriharu Watanabe, Norio Narita, Akihiko Fukui, Bun’ei Sato, Keisuke Isogai, John H. Livingston, Jerome P. de Leon, Daniel Huber, Yugo Kawai, Yuya Hayashi, Masashi Omiya, Hideyuki Izumiura, Akito Tajitsu, Keivan G. Stassun, Eric Girardin, Giuseppe Marino, Antonio Frasca, Giovanni Catanzaro, Javier Alonso-Santiago, Manfred Raetz, Stephanie Striegel, Nobuhiko Kusakabe, and Motohide Tamura
Source/Credit: University of Tokyo
Edited by: Scientific Frontline
Reference Number: astr091826_01
