Hot Jupiters, gas giants that orbit scorchingly close to their stars, are a cosmic enigma. Their formation far from their current positions and subsequent migration inward has puzzled scientists for years. A recent discovery, however, is shedding light on this celestial ballet. Astronomers at MIT, Penn State University, and other institutions have identified a hot Jupiter “progenitor” – a planet in the midst of its transformation.
This intriguing planet, dubbed TIC 241249530b, orbits a star approximately 1,100 light-years from Earth. Its claim to fame? An exceptionally “eccentric” orbit, the most extreme observed to date. Imagine a planet in our solar system swinging 10 times closer to the sun than Mercury, then catapulting outward past Earth, only to loop back again – that’s the wild ride TIC 241249530b is on.
Adding to its peculiarity, the planet travels in a “retrograde” direction, opposite to its star’s rotation, unlike the planets in our solar system. This unusual behavior, the researchers believe, holds the key to its evolution.
Through intricate simulations, the team determined that TIC 241249530b is engaged in a gravitational dance with its host star and a second, more distant star in a binary system. This intricate interaction is causing the planet to gradually spiral inward, its orbit shrinking over time.
This new planet supports the theory that high eccentricity migration should account for some fraction of hot Jupiters,
explains Sarah Millholland, assistant professor of physics at MIT’s Kavli Institute for Astrophysics and Space Research.
We think that when this planet formed, it would have been a frigid world. And because of the dramatic orbital dynamics, it will become a hot Jupiter in about a billion years, with temperatures of several thousand kelvins. So it’s a huge shift from where it started.
Currently, TIC 241249530b takes 167 days to complete one orbit. However, the simulations predict that in a billion years, its orbit will tighten into a close circle, whipping around its star in a matter of days. This dramatic shift will transform the planet into a sweltering hot Jupiter.
The discovery, published in the journal Nature, was made possible by data from NASA’s Transiting Exoplanet Survey Satellite (TESS). TESS detected a telltale dip in the host star’s light, indicating a planet crossing its path. Subsequent measurements of the star’s “wobble” confirmed the presence of the massive planet and its unusual orbit.
“This new planet experiences really dramatic changes in starlight throughout its orbit,” Millholland notes. “There must be really radical seasons and an absolutely scorched atmosphere every time it passes close to the star.”
This finding provides compelling evidence for the high eccentricity migration theory, suggesting that a significant portion of hot Jupiters may have formed through this process of orbital upheaval.
Smadar Naoz, a professor of physics and astronomy at the University of California at Los Angeles, who was not involved in the study, remarks, “It is really hard to catch these hot Jupiter progenitors ‘in the act’ as they undergo their super eccentric episodes, so it is very exciting to find a system that undergoes this process. I believe that this discovery opens the door to a deeper understanding of the birth configuration of the exoplanetary system.”
The discovery of TIC 241249530b offers a rare glimpse into the dynamic evolution of planetary systems, highlighting the incredible diversity and often chaotic beauty of the cosmos.
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