Astronomers Discover Early Version of a Hot Jupiter
Astronomers have discovered a kind of early version of a hot Jupiter. The eccentric orbit of this planet reveals crucial information about how hot Jupiters develop.
Currently, we know of the existence of more than 5,600 exoplanets residing in just over 4,000 different star systems. And now, we can add an exceptional exoplanet to that list. Researchers have stumbled upon a ‘precursor’ hot Jupiter, and this planet boasts an extraordinarily remarkable orbit.
Orbital Characteristics
The new planet, named TIC 241249530 b by astronomers, resides around a star approximately 1,100 light-years from Earth. This planet, which is about five times as massive as Jupiter, follows a very ‘eccentric’ orbit around its star. This means it closely approaches its parent star, gets flung far away, and then returns in a narrow, elliptical orbit. If this planet were part of our Solar System, it would come ten times closer to the Sun than Mercury before swinging past Earth and then returning. Scientists have noted that the orbit of this planet holds the highest eccentricity among all known planets so far.
Such a remarkable orbit likely results in temperatures on the planet ranging from those of a summer day to temperatures high enough to melt titanium. “This new planet experiences significant variations in the amount of starlight it receives,” says researcher Sarah Millholland. “Each time the planet gets close to its star, there are extreme seasonal changes, scorching its atmosphere.”
Retrograde Motion
And as if that weren’t enough, researchers discovered that the exoplanet moves in a backward direction around its star, opposing the rotation of its parent star. This is something astronomers rarely see in most other exoplanets and is also unheard of within our own Solar System.
A Hot Jupiter in the Making
How did TIC 241249530 b acquire this strange orbit? Researchers have an idea. The team simulated the orbital dynamics and found that the highly eccentric and retrograde orbit of the planet suggests it is likely evolving into a hot Jupiter. This means the exoplanet is, in fact, a hot Jupiter in the making. This is quite special; before this discovery, only one other planet was known to be considered an early hot Jupiter: HD 80606 b, which also has a peculiar orbit. “Astronomers have been searching for exoplanets that are precursors to hot Jupiters or in the middle of their migration process for more than two decades,” says researcher Arvind Gupta. “I was incredibly surprised and excited to find one. It is exactly what I had hoped for.”
In brief, researchers suspect that TIC 241249530 b is currently evolving into a hot Jupiter through a process called ‘high-eccentricity migration,’ in which a planet’s orbit wobbles and gradually shrinks due to interactions with another star or planet in a much larger orbit. In the case of TIC 241249530 b, researchers identified that the planet orbits a parent star, which in turn orbits a second star in a binary star system. The arrangement of the orbits resembles a circus performer spinning a hoop around her waist while simultaneously twirling a second hoop around her wrist. Interactions between the two orbits—the planet’s and its star’s—have caused the planet to slowly migrate closer to its star. “It’s a very profound process because the changes in the planet’s orbit are considerable,” explains Millholland. “It’s a complex choreography of orbits unfolding over billions of years, and the planet is merely along for the ride.”
Future Evolution
The planet currently has an elliptical orbit and completes one revolution around its star in about 167 days. However, scientists predict that in about a billion years, the planet will migrate to a much tighter, circular orbit, rounding its star every few days. “At that point, the planet will have fully evolved into a hot Jupiter,” says Millholland. The discovery of an exoplanet before its migration has occurred is valuable as it provides crucial insights into how hot Jupiters form, stabilize, and evolve over time. “We cannot literally rewind planetary migration and observe it in real-time, but this exoplanet serves as a snapshot of that process,” Gupta comments. “Planets like these are incredibly rare and challenging to find. We hope this can help unravel the story of hot Jupiter formation.”
Overall, the study of TIC 241249530 b’s evolution offers fascinating insights into the origin and development of hot Jupiters. “This research, along with other studies, shows that high-eccentricity migration plays a role in the formation of hot Jupiters,” notes Millholland. “This system illustrates just how incredibly diverse exoplanets can be. They are mysterious worlds with unusual orbits that reveal their formation history and future destination. And for this planet, the journey is not yet over.”
