Astronomers have discovered a peculiar exoplanet within our galaxy that breaks records for its type.
To date, more than 5,000 exoplanets—planets orbiting stars outside our solar system—have been identified. These planets come in an astonishing variety of shapes, sizes, and densities.
For instance, PSR J1719-1438 b, which orbits a rapidly spinning neutron star, is 324 times as dense as Earth, making it the densest planet found to date. On the other hand, exoplanets in the Kepler 51 system are so light that their density rivals that of cotton candy.
Now, a new exoplanet has been discovered that breaks density records within its planetary class.
Say hello to K2-360 b. An international team of researchers, including scientists from the Niels Bohr Institute in Denmark and the Astrobiology Center in Tokyo, Japan, has investigated this remarkable exoplanet.
A Super-Earth with Extreme Features
K2-360 b resides in the K2-360 solar system, orbiting a star similar to our Sun. The exoplanet is classified as a super-Earth—larger than Earth but smaller than Neptune.
The planet is 1.6 times larger than Earth and orbits its host star in just 21 hours, meaning a year on K2-360 b is shorter than a single day on Earth. This places it in the category of ultra-short period planets.
What sets K2-360 b apart is its extreme density.
The planet is 7.7 times denser than Earth—comparable to lead—and its surface is covered in lava due to its close proximity to its star. This makes K2-360 b the densest planet ever observed in its class.
Moreover, observations show that the planet has a large iron core, which constitutes 48% of its mass. Researchers believe K2-360 b is the remnant of a much larger gas planet, possibly resembling Neptune, whose atmosphere was stripped away over time.
K2-360 b shares its system with a larger sibling, K2-360 c, a planet at least 15 times the mass of Earth that completes an orbit every 9.8 days. However, K2-360 c’s orbit is tilted, making it unobservable from Earth.
Scientists theorize that K2-360 b once followed an elliptical orbit around its star. Over time, gravitational forces from K2-360 c likely pushed K2-360 b into a closer, circular orbit. Intense radiation from the star then blew away K2-360 b’s gaseous atmosphere, leaving behind a dense, rocky core.
The K2-360 system offers valuable insights into planetary evolution under extreme conditions. Researchers plan to continue studying this system to better understand how planets behave and survive in such harsh environments.
The findings have been published in the journal Scientific Reports.
