The Exoplanet KELT-21 b: A Gas Giant on a Close Orbit
Exoplanets, planets that exist beyond our solar system, offer a fascinating glimpse into the vast diversity of planetary bodies that populate the universe. Among these, the gas giants are especially intriguing due to their massive sizes and often extreme conditions. One such exoplanet is KELT-21 b, discovered in 2018, which has garnered attention due to its unique characteristics and its proximity to its host star.
Discovery of KELT-21 b
KELT-21 b was discovered in 2018 as part of the ongoing search for exoplanets by the Kilodegree Extremely Little Telescope (KELT) survey. The KELT survey is a project aimed at detecting transiting exoplanets by observing stars with relatively low magnitudes. This survey has provided a wealth of information on exoplanets, and KELT-21 b is one of the many significant finds made by the mission.
The planet was identified using the transit method, a technique that involves monitoring the light emitted by a star and detecting periodic dimming caused by an exoplanet passing in front of it. This method is one of the most successful ways of identifying exoplanets, especially those that are relatively large and in close orbits around their host stars.
Characteristics of KELT-21 b
KELT-21 b is classified as a gas giant, similar to Jupiter in our own solar system. These planets are primarily composed of hydrogen and helium and lack a solid surface. This characteristic distinguishes them from terrestrial planets, which are primarily rocky. Gas giants, including KELT-21 b, are typically much larger and more massive than Earth, and they possess thick atmospheres with varying weather patterns and storm systems.
The size and mass of KELT-21 b are notable. With a mass 3.91 times that of Jupiter and a radius 1.586 times that of Jupiter, it is a substantial planet in terms of both mass and size. Its massive size and close proximity to its star make it a particularly interesting subject for astronomers to study, especially when considering the extreme conditions such a planet would experience due to its environment.
Orbital Characteristics
One of the most remarkable features of KELT-21 b is its proximity to its host star. The planet orbits its star at a distance of just 0.05224 AU, which is incredibly close when compared to the Earth-Sun distance of 1 AU. This close orbit places KELT-21 b in the category of hot Jupiters, a class of exoplanets known for their large sizes and high temperatures due to their tight orbits around their parent stars.
The orbital period of KELT-21 b is 0.009856262 days, or approximately 14.9 hours. This is a significantly shorter period than that of any planet in our solar system, including Mercury, which has an orbital period of about 88 Earth days. The short orbital period means that KELT-21 b completes an entire orbit around its star in just under 15 hours, which leads to an extremely hot environment.
Given the close proximity of KELT-21 b to its star, its temperature is likely to be exceedingly high, and the planet is expected to experience intense radiation and tidal forces. These factors contribute to the planet’s extreme atmospheric conditions, which could include high wind speeds, intense storms, and possibly even massive cloud formations made up of various chemicals.
Orbital Eccentricity
KELT-21 b’s orbit has an eccentricity of 0.0, meaning that it follows a perfectly circular orbit. This is an important characteristic, as many exoplanets, particularly those in tight orbits, can have elliptical orbits that bring them closer to their star at certain points and farther away at others. A perfectly circular orbit, as seen in KELT-21 b, means the planet maintains a constant distance from its star throughout its orbit. This could suggest a more stable environment compared to planets with highly eccentric orbits, although the extreme closeness of the planet to its star would still result in harsh conditions.
Stellar Magnitude and Observations
The host star of KELT-21 b, like many stars in the KELT survey, has a stellar magnitude of 10.484, which places it in the category of relatively faint stars. Despite this, the KELT survey’s advanced telescopes and detection methods, such as the transit method, have allowed for the successful identification of exoplanets orbiting these stars. The faintness of the star makes KELT-21 b an interesting target for study, as it represents an example of a planet orbiting a less luminous, yet detectable, star.
The observation of such planets provides valuable insights into the wide range of exoplanets that can exist in the universe, from those in close orbits to those far away from their stars. These discoveries challenge our understanding of planet formation and the conditions that lead to the creation of different types of planets.
Conclusion
KELT-21 b is an excellent example of the diversity and complexity of exoplanets discovered through ongoing astronomical surveys. Its characteristics—such as its large size, close orbit, and lack of orbital eccentricity—make it a prime subject of study for astronomers interested in gas giants and the factors that influence their environments.
The planet’s discovery highlights the important role that exoplanet surveys like KELT play in broadening our understanding of the universe. As technology continues to advance and new techniques for detecting exoplanets are developed, we can expect to learn even more about planets like KELT-21 b and others in similarly extreme environments. These findings have the potential to inform our understanding of planet formation, orbital dynamics, and the potential for habitable worlds in other star systems.