Is There a Planet Larger Than Its Sun but Not More Massive?

The universe is a vast and mysterious place where many celestial bodies exist in unexpected proportions. One such enigma is the rare occurrence of planets that are larger than their suns but not necessarily more massive. In this article, we will explore this peculiar phenomenon and its intricate details, focusing on red dwarfs and other stellar anomalies.

Red Dwarf Stars: Small but Dense

Red dwarf stars are among the smallest and faintest stars in the universe, with diameters that can be as small as approximately 15% of our Sun. Due to their compact nature, these stars require a significant amount of mass to sustain nuclear fusion in their cores. Consequently, they are quite dense compared to planets.

While other stars might have a vast volume, red dwarfs might actually be smaller in volume than some gaseous planets like Jupiter. This is because gas giants are less dense than the average density of water on Earth, allowing them to expand to larger proportions without significantly increasing their mass.

Neutron Stars and Planetary Systems

Before delving into more recent discoveries, it is worth noting that neutron stars, which are the remnants of supernovae, have a diameter of only about 10 kilometers. The first known planetary system, consisting of three rocky planets smaller than Earth, was found orbiting a neutron star. Although none have been confirmed, it is not entirely impossible for such systems to exist.

Interestingly, there is a size trend in the universe that balances out the increase in gravity with additional mass. Objects, from approximately 1 Jupiter mass (J) to 80 J, have roughly the same size and volume. As mass increases, density increases, but size remains almost the same. This means that the largest planets, brown dwarfs, and the very smallest red dwarf main sequence stars are all roughly the same size.

The Smallest and Largest Known Extremes

The smallest known star is a red dwarf with a diameter of about 0.9 J. On the other hand, the largest known gas giant planets have diameters close to that of Jupiter. There are a few exceptions where planets can be larger, usually due to their outer atmospheres being puffed up by an external heat source, resulting in diameters of about 2.0 J.

A key question remains: can very small red dwarfs during their formation generate a massive gas giant planet? Or how likely is it for a star as puny as the smallest red dwarfs to capture a Jupiter mass object as a planet? If possible, it opens the possibility of star systems with a red dwarf star 0.9 to 1.0 J in diameter, hosting a planet 1.0 to 1.5 J in diameter.

Observational Challenges and Scientific Fascination

The observational study of such a system would be particularly intriguing. These systems could mimic a total solar eclipse, allowing scientists to study the corona of another star in detail. This unique setup would enable us to gain insights into the intricacies of planetary formation and star evolution, pushing the boundaries of our understanding of the cosmos.

In conclusion, the universe continues to surprise us with its vast array of celestial phenomena, including planets larger than their stars. The study of red dwarfs and other stellar anomalies provides invaluable data for astronomers and highlights the immense complexity of our universe. Through continued research, we will undoubtedly uncover more secrets hidden within the vast expanse of space.