Understanding Planetary Mass and Stellar Mass: A Comparative Analysis
Planets and stars vary widely in terms of their mass, with the most massive planet surpassing the least massive star in terms of mass. This article delves into the specifics of the most massive known planet, the least massive stars, and the comparison between them, highlighting the significant role of mass in determining whether a celestial body is classified as a star or a planet.
The Most Massive Planet: HD 100546 b
The most massive known planet is HD 100546 b, which can have a mass approaching ten times that of Jupiter. This is notably significant because the average mass of the smallest red dwarfs, the least massive stars, is around 0.08 solar masses, or approximately 80 times the mass of Jupiter. While the most massive exoplanets, such as HD 100546 b, are much less massive than the least massive stars, the comparison is fascinating. To provide a more specific example, the largest known gas giant, HAT-P-67b, is only about a third of Jupiter's mass but is twice its size, with a diameter of 285,350 kilometers. This example underscores the importance of mass over size in determining whether a celestial body is a planet or a star.
The Least Massive Stars: Red Dwarfs and Brown Dwarfs
The smallest known star is EBLM J0555-57Ab, which has a diameter of 118,850 kilometers, approximately 85 times the diameter of Jupiter. Red dwarfs, which are the smallest stars still producing energy by fusion, have diameters around 120,000 kilometers, similar to EBLM J0555-57Ab. These stars have masses around 0.08 solar masses, which is 80 times the mass of Jupiter. The key distinction here is that while red dwarfs can have a similar diameter to the largest exoplanets, their mass is significantly higher, exceeding that of the most massive planets.
Brown Dwarfs: A Fitting Comparison
Brown dwarfs, often classified as sub-stellar objects, have masses ranging from 0.01 to 0.08 solar masses, making them comparable to or even slightly more massive than the largest exoplanets. Brown dwarfs are not as large as red dwarfs, with a diameter similar to that of a white dwarf, which is around 3,300 kilometers. However, their mass is sufficient to create significant pressure and potentially trigger fusion in their cores, making them a unique category of objects.
Differences Between Mass and Size
The distinction between a celestial body being classified as a star or a planet is primarily determined by its mass. Size alone does not determine this classification. In the case of the largest gas giant, HAT-P-67b, and the smallest known star, EBLM J0555-57Ab, this principle is evident. While HAT-P-67b is twice the size of Jupiter but has only one-third of Jupiter's mass, EBLM J0555-57Ab has 85 times the diameter of Jupiter but has a mass 80 times that of Jupiter. This highlights the critical role of mass in classifying celestial bodies as stars or planets.
Conclusion
Understanding the mass of celestial bodies is crucial in distinguishing between planets and stars. While the most massive planets, such as HD 100546 b, can have masses approaching ten times that of Jupiter, they generally do not surpass the mass of the least massive stars, such as red dwarfs. However, brown dwarfs, with masses ranging from 0.01 to 0.08 solar masses, can be comparable to or slightly more massive than the largest exoplanets. This comparison underscores the significance of mass in determining whether a celestial body falls into the category of a planet or a star.
Keywords: massive planets, least massive stars, exoplanets, red dwarfs, brown dwarfs