They detect a planet "very eccentric" on its way to becoming a hot Jupiter

Jul 17. () –

Hot Jupiters are some of the most extreme planets in the galaxy. These scorching hot worlds They are as massive as Jupiter and orbit very close to their star.orbiting in just a few days, compared with our own gas giant’s leisurely 4,000-day orbit around the Sun.

Scientists suspect, however, that hot Jupiters were not always so hot and may in fact have formed as “Cold Jupiters” in colder, more distant environmentsBut how they evolved into the star-hugging gas giants astronomers observe today remains a big mystery. The researchers report their findings in the journal Nature.

Now, astronomers from MIT and Pennsylvania State University (United States), among others, They have discovered a “progenitor” of hot Jupiter, a kind of young planet that is in the process of becoming a hot Jupiter.And its orbit is providing some answers to the evolution of hot Jupiters.

The new planet, which astronomers have named TIC 241249530 b, orbits a star about 1,100 light-years from Earth. The planet orbits its star in a highly “eccentric” orbit, meaning it comes very close to it before moving away and then retreating in a tight elliptical loop. If the planet were part of our solar system, it would come ten times closer to the Sun than Mercury, before speeding away, passing just in front of Earth, and then turning around.

According to scientists’ calculations, the planet’s elongated orbit has the highest eccentricity of any planet detected to date. The new planet’s orbit is also unique for its “retrograde” orientation. Unlike Earth and other planets in the solar system, which orbit in the same direction as the Sun, the new planet is traveling in a direction opposite to the rotation of its star.

The team ran orbital dynamics simulations and found that the planet’s highly eccentric and retrograde orbit are signs that it is likely evolving toward a hot Jupiter, through “high-eccentricity migration,” a process by which a planet’s orbit progressively wobbles and shrinks as it interacts with another star or planet in a much wider orbit.

In the case of TIC 241249530 b, researchers determined that the planet orbits a primary star that in turn orbits a secondary star, as part of a binary star system. Interactions between the two orbits (that of the planet and its star) have caused the planet to gradually approach its star over time.

The planet’s orbit is currently elliptical, taking about 167 days to complete a full orbit around its star. Researchers predict that within a billion years, the planet will migrate to a much tighter, more circular orbit, circling its star every few days. At that point, the planet will have fully evolved into a hot Jupiter.

“This new planet supports the theory that high-eccentricity migration should explain a fraction of hot Jupiters“We think that when this planet formed, it would have been a frigid world. And because of dramatic orbital dynamics, it will become a hot Jupiter in about a billion years, with temperatures of several thousand degrees Kelvin. So it’s a big change from where it started.”

The new planet was first detected in data taken by NASA’s Transiting Exoplanet Survey Satellite (TESS), an MIT-led mission that monitors the brightness of nearby stars for “transits,” or brief dips in starlight that could indicate the presence of a planet passing in front of a star’s light and temporarily blocking it.

Before this detection, astronomers knew of only one other planet, HD 80606 b, which was thought to be an early hot Jupiter. That planet, discovered in 2001, held the record for the highest eccentricity. “This new planet experiences really dramatic changes in starlight along its orbit,” Millholland says.There must be really radical seasons and an absolutely scorching atmosphere every time it passes close to the star.“.

The team’s observations, along with their simulations of the planet’s evolution, support the theory that hot Jupiters may form through high-eccentricity migration, a process by which a planet is gradually moved into place through extreme changes in its orbit over time.

“Not only from this study, but also from other statistical studies, it is clear that a fraction of hot Jupiters are due to high eccentricity migrations.“Millholland said. “This system highlights the incredible diversity that exoplanets can have. They’re other mysterious worlds that can have crazy orbits that tell the story of how they got that way and where they’re headed. In the case of this planet, its journey isn’t over yet.”