A Mercury-like planet the size of the Earth orbits 100 times closer to its star, K2-229, as the Earth makes the sun.
Credit: L. Calçada / ESO
Scientists have discovered a metal-heavy cannonball of an exoplanet resembling an earth-sized version of Mercury.
This newly discovered world could help illuminate the secrets of the birth and development of Mercury.
Earlier research suggests that Earth, Venus and Mars have metal nuclei that make up only about one third of the mass of their planets. In contrast, Mercury consists mainly of metal with a metallic core, which accounts for about two-thirds of the mass of the planet. [Inside Planet Mercury (Infographic)]
It remains hotly debated why Mercury differs so much from its rocky siblings. Now researchers have discovered an alien version of Mercury that could better explain the history of the innermost world of the solar system.
Scientists analyzed three planets orbiting an orange dwarf called K2-229, which is a bit cooler and smaller than the Sun about 339 light-years from Earth in the Virgo constellation. They focused on K2-229 b, the world closest to the K2-229, orbiting about 100 times closer to its star than the Earth's sun.
K2-229 b & s daytime temperatures can reach a blazing 3,737 degrees Fahrenheit (2,058 degrees Celsius), the researchers found. In comparison, the mercury, which is about 2.6 times closer to the sun than the Earth, has daytime temperatures of only about 801 degrees Fahrenheit (427 degrees Celsius).
The researchers analyzed repeated wobbles in the movements of K2-229, which was a sign of the attraction of K2-229 b, tearing it back and forth. Since the gravitational field strength of a planet depends on its mass, the research team estimates that the innermost planet of K2-229 is about 2.59 times the mass of the Earth. (By comparison, Mercury is only about 5.5 percent of Earth's mass.)
Analyzing K2-229 b when it happened before its star, the scientists found that the planet was only about 1,165 times as large Big was like the diameter of the earth. All in all, this exoplanet is about 60 percent more dense than Earth.
Assuming that K2-229b has a metallic nucleus like Earth's other planets and the solar system, the researchers estimate that its nucleus is likely to make up more than two-thirds of the mass of the exoplanet. This makes K2-229 a cannonball planet like Mercury.
"Almost all of the low-mass small planets discovered to date have compounds that were very similar to our Earth, and we began to think that Earth's mass composition is the typical and Mercury is the only exception," said Co -Author Vardan Adibekyan, astronomer at the Institute of Astrophysics and Space Science in Porto, Portugal, opposite Space.com. "But now we see that there are more exceptions, and as the number of such" exceptions "increases, they will become typical."
K2-229 b is probably metal-heavy nature that is strongly associated with chemical composition of the star contrasts. This suggests that K2-229b could have changed dramatically over time, the researchers said. Perhaps his original crust and part of his mantle were evaporating because of its extraordinary proximity to the heat and magnetic field of its star, or perhaps it was experiencing a huge impact that demolished a good portion of its outer layers, the scientists noted.
The similarities between Mercury and K2-229b suggest that they could share a common history. Therefore, researchers could learn more about K2-229 b if they were to learn more about the formation and evolution of Mercury and other planets.
"Our team and several other teams are working hard to discover more systems like this that will eventually help us make a firm conclusion about the origin of Mercury and Exo-Mercuries," Adibekyan said.
The scientists presented their findings online on March 26 in the journal Nature Astronomy