What is hot planet
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Understanding Hot Planets: Hot Jupiters and Hot Earths
Introduction to Hot Planets
Hot planets, particularly hot Jupiters and hot Earths, are a fascinating category of exoplanets characterized by their close proximity to their host stars, resulting in extremely high surface temperatures. These planets have been the subject of extensive research due to their unique properties and the insights they provide into planetary formation and migration.
Hot Jupiters: Characteristics and Discoveries
Definition and General Properties
Hot Jupiters are gas giant exoplanets with masses comparable to or greater than Jupiter, but they orbit very close to their host stars, typically within 0.1 AU. This proximity results in very short orbital periods, often less than 10 days, and high surface temperatures1 3 5.
Recent Discoveries
NASA's Transiting Exoplanet Survey Satellite (TESS) has significantly contributed to the discovery and characterization of hot Jupiters. For instance, the TESS Grand Unified Hot Jupiter Survey reported the discovery of 10 new hot Jupiters, with orbital periods ranging from 2 to 10 days and masses between 0.2 and 2.2 Jupiter masses1. Another study added 20 new hot Jupiters, all with orbital periods shorter than 7 days, further enriching the sample available for demographic studies3.
Formation and Migration Theories
The formation and migration of hot Jupiters are still subjects of active research. One theory suggests that these planets form further out in their star systems and migrate inward through interactions with the protoplanetary disk or other planets. Some hot Jupiters exhibit retrograde orbits, which are thought to result from complex gravitational interactions, such as secular perturbations in multi-planet systems7.
Hot Earths: Characteristics and Discoveries
Definition and General Properties
Hot Earths, also known as ultra-short-period planets, are terrestrial planets with very short orbital periods, sometimes as short as a few hours. These planets are so close to their stars that any initial hydrogen/helium atmosphere is likely lost to photoevaporation, leaving behind rocky cores2.
Recent Discoveries
A homogeneous analysis of 11 known hot Earths revealed that most of these planets have compositions similar to Earth, with a mix of iron and rock. However, some, like K2-141b and K2-229b, show higher iron fractions, indicating diverse formation histories2. Additionally, the discovery of GJ 3473 b, a hot Earth-sized planet with a mass of 1.86 Earth masses and an orbital period of just over a day, highlights the variety of these planets9.
Potential for Atmospheric Studies
Hot Earths are prime candidates for atmospheric studies using advanced telescopes like the James Webb Space Telescope. These studies can provide insights into the atmospheric composition and surface properties of these planets, enhancing our understanding of planetary evolution under extreme conditions8.
Conclusion
Hot planets, including hot Jupiters and hot Earths, offer a unique window into the processes of planetary formation and migration. The ongoing discoveries and characterizations by missions like TESS are crucial for building comprehensive models of these intriguing worlds. As research continues, we can expect to uncover even more about the diverse and dynamic nature of hot planets.
Sources and full results
Most relevant research papers on this topic
The TESS Grand Unified Hot Jupiter Survey. I. Ten TESS Planets
The TESS satellite has discovered 10 new hot Jupiters, ranging in mass from 0.2 to 2.2 Jupiter masses, orbiting bright F and G stars with orbital periods ranging from 2 to 10 days.
Homogeneous Analysis of Hot Earths: Masses, Sizes, and Compositions
Hot Earths show a mostly Earth-like composition (35% iron and 65% rock), with some exceptions, and all are less massive than 8 M, suggesting 8 M is the critical mass for runaway accretion.
The TESS Grand Unified Hot Jupiter Survey. II. Twenty New Giant Planets
TESS data has identified 20 new hot Jupiters with orbital periods shorter than 7 days and bright FGK stars, improving our understanding of these distant planets.
A hot super-Earth planet in the WASP-84 planetary system
WASP-84 c, a hot super-Earth with an equilibrium temperature of 1300 K, has been discovered in the WASP-84 planetary system, suggesting that some hot Jupiters coexist with low-mass planets in compact orbital architectures.
TESS Delivers Five New Hot Giant Planets Orbiting Bright Stars from the Full-frame Images
TESS has discovered five new hot and warm Jupiters orbiting bright stars, with TOI-628 b being the most massive and TOI-1478 b being a warm Jupiter in a circular orbit around a near-solar analog.
Transiting exoplanets from the CoRoT space mission - IX. CoRoT-6b: a transiting “hot Jupiter” planet in an 8.9d orbit around a low-metallicity star
CoRoT-6b is a transiting "hot Jupiter" planet in an 8.9d orbit around a low-metallicity star, with a mass close to 3 times that of Jupiter and a high 7 Li abundance.
Hot Jupiters from secular planet–planet interactions
Hot Jupiters can be produced in retrograde orbits with respect to the total angular momentum through secular planet-planet interactions, unlike distant stellar mass perturbers.
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