Is there a star that orbits a planet
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Star Orbiting a Planet: A Scientific Exploration
Introduction to Star-Planet Interactions
The dynamics of star-planet interactions have been a subject of intense study, particularly focusing on how these interactions influence the evolution of planetary orbits. When planets form from the protoplanetary disk, their orbits are shaped by tidal interactions, friction, gravitational drag, and changes in the mass of the star and planet1. These factors can lead to significant changes in the distance between planets and their host stars, potentially causing planets to be engulfed by their stars or even destroyed1.
Evolution of Planetary Orbits
Tidal Interactions and Stellar Rotation
Tidal interactions, especially in close-in star-planet systems, play a crucial role in the evolution of planetary orbits. The rotation of the host star significantly impacts these processes. Rapid initial stellar rotation and efficient angular momentum transport within the star can expand the region devoid of planets after the pre-main-sequence (PMS) phase2. This phenomenon, known as the "planet desert," is observed in the distribution of exoplanets orbiting solar-mass stars2.
Effects of Stellar Evolution
As stars evolve from the main sequence to the red giant phase, their expansion can drastically alter the orbits of surrounding planets. For instance, the discovery of a planetary-mass body orbiting the star V391 Pegasi, which is on the extreme horizontal branch of the Hertzsprung-Russell diagram, demonstrates that planets can survive the red giant expansion of their parent stars if they are at a sufficient distance3. This finding is significant as it shows that planets within 2 astronomical units (au) can endure the dramatic changes in their host stars' sizes3.
Notable Discoveries of Planets Orbiting Evolved Stars
HD 1397b: A Transiting Warm Giant Planet
The discovery of HD 1397b, a transiting warm giant planet orbiting a subgiant star, highlights the complexities of planetary systems around evolved stars. HD 1397b orbits its host star with a period of 11.54 days and has a moderately eccentric orbit5. The host star, having departed from the main sequence, provides a unique opportunity to study the properties of giant planets in such environments5.
EPIC 249893012: A System with Three Transiting Planets
Another intriguing system is EPIC 249893012, which hosts three transiting planets: one super-Earth and two sub-Neptunes. This system orbits a slightly evolved star that is just leaving the main sequence, making it an excellent candidate for studying the dynamics of planetary systems around evolving stars8. The inner planet, with a mass of 8.75 Earth masses, has a density consistent with a rocky composition, while the outer planets suggest the presence of thick atmospheres8.
Conclusion
While the concept of a star orbiting a planet remains speculative, the study of star-planet interactions and the evolution of planetary orbits around evolving stars provides valuable insights into the dynamics of such systems. Discoveries like V391 Pegasi and HD 1397b demonstrate that planets can survive significant changes in their host stars, offering a glimpse into the potential complexities of star-planet relationships. As our understanding of these interactions deepens, the possibility of finding more unique and diverse planetary systems continues to grow.
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Most relevant research papers on this topic
Star-planet interactions
Dynamical tides significantly affect planetary orbits during the pre-main-sequence phase for fast-rotating stars, but have no significant effect during the red giant branch phase.
Star-planet interactions
Rapid initial stellar rotation and efficient angular momentum transport contribute to the enlargement of the domain devoid of planets after the pre-main-sequence phase.
A giant planet orbiting the ‘extreme horizontal branch’ star V 391 Pegasi
This discovery of a planet orbiting a post-red-giant star shows that planets with orbital distances less than 2 au can survive the red-giant expansion of their parent stars.
Highly CitedProtostars and Planets
Extrasolar planets orbiting stars outside our solar system have been discovered, but their characteristics and origins remain a subject of intense interest and debate.
Highly CitedHD 1397b: A Transiting Warm Giant Planet Orbiting A V = 7.8 mag Subgiant Star Discovered by TESS
HD 1397b is a transiting warm giant planet orbiting a subgiant star, with a mass of and a radius of, and is one of the brightest systems to host a transiting planet.
Direct Imaging of Multiple Planets Orbiting the Star HR 8799
Three planets orbiting the star HR 8799 have been identified, with masses between 5 and 13 times that of Jupiter, indicating a scaled-up version of our solar system.
Highly CitedPlanets Orbiting Other Suns
Planets orbiting other stars are confirmed, with 5% of main-sequence stars harboring companions within 3 AU, suggesting diverse systems and the need for special initial conditions for stable coplanar orbits.
Highly CitedThree planets transiting the evolved star EPIC 249893012: a hot 8.8-M⊕ super-Earth and two warm 14.7 and 10.2-M⊕ sub-Neptunes
This study discovers a new planetary system with one super-Earth and two sub-Neptunes orbiting an evolved star, offering potential for further study on dynamical aspects.
Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1
Seven Earth-like planets orbit TRAPPIST-1, with temperatures low enough for liquid water on their surfaces, suggesting they formed further from the star and migrated inwards.
Very Rigorous JournalHighly CitedTemperate Earth-sized planets transiting a nearby ultracool dwarf star
Three short-period Earth-sized planets have been observed transiting an ultracool dwarf star, with the third likely receiving significantly less irradiation than Earth.
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