Outermost planet
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The Outermost Planets in Various Planetary Systems
Outermost Planets in the Solar System: Uranus and Neptune
Uranus and Neptune are the outermost planets in our Solar System. These ice giants are primarily composed of hydrogen, helium, and water, with significant amounts of ammonia and methane. Their internal structures are complex, with potential non-adiabatic and inhomogeneous interiors, which contribute to uncertainties in our understanding of their formation and thermal evolution. Improved observational constraints on their physical parameters, such as gravitational and magnetic fields, rotation rates, and atmospheric compositions, are essential for advancing our knowledge of these distant planets.
Outermost Planets in Exoplanetary Systems
Kepler-186 System: Kepler-186f
Kepler-186f is the outermost planet in the Kepler-186 system, which consists of five Earth-sized planets orbiting a small star. Kepler-186f is only 10% larger than Earth and completes its 130-day orbit within the habitable zone, where liquid water could potentially exist on its surface. This discovery is significant as it highlights the potential for Earth-like conditions on planets outside our Solar System.
TRAPPIST-1 System: TRAPPIST-1h
The TRAPPIST-1 system, orbiting an ultra-cool dwarf star, includes seven Earth-sized planets. The outermost planet, TRAPPIST-1h, has an orbital period of 18.764 days and a radius of 0.715 Earth radii. It is located at the system's snow line, with an equilibrium temperature of 169 K, indicating it is likely too cold for liquid water to exist on its surface. The system's planets are linked by a complex chain of three-body resonances, making it a fascinating subject for studying planetary dynamics.
TOI-700 System: TOI-700d
TOI-700d is the outermost planet in the TOI-700 system, which orbits an M2 dwarf star. This planet has a radius of 1.19 Earth radii and resides within the habitable zone, receiving about 86% of the insolation that Earth receives from the Sun. The low stellar activity of TOI-700 makes it an excellent candidate for studying potentially rocky planets and their atmospheres.
HD 69830 System: HD 69830d
The HD 69830 system features three Neptune-mass planets, with the outermost planet, HD 69830d, having an orbital period of 197 days. This planet likely has a significant gaseous envelope surrounding a rocky/icy core and orbits within the habitable zone of its star . The system's stability and the presence of an asteroid belt within 1 AU add to its interest for further study.
Conclusion
The study of outermost planets, both within our Solar System and in exoplanetary systems, provides valuable insights into planetary formation, composition, and potential habitability. From the ice giants Uranus and Neptune to Earth-sized exoplanets like Kepler-186f and TOI-700d, these distant worlds continue to intrigue scientists and expand our understanding of the universe.
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