- Astronomers discover a massive planet orbiting a small star.
- The mass of the planet is way more than what current theoretical models predict.
- It lies 30 light-years away from Earth and has a mass nearly half as big as Jupiter.
Like our solar system, there are millions of planets out there orbiting different types of stars. So far, astronomers have discovered more than 4,000 of those exoplanets (planets outside our solar system).
However, only 10% of detected exoplanets are orbiting M-type dwarfs (whose masses are less than 0.6 solar masses) despite the fact that M-type dwarfs are the most numerous stellar type in the galaxy.
Recently, a research team at an observatory in southern Spain made a surprising discovery – they found a massive planet orbiting a small star. The mass of the planet is way more than what current theoretical models predict. Another team of scientists at the University of Bern analyzed the formation process of this unusual exoplanet.
The research consortium named CARMENES detected this mysterious exoplanet. CARMENES is made up of 10 centers and universities in Spain and Germany, with the aim of designing, developing and operating a large telescope for detecting planets around the smallest stars.
The mysterious planet was observed by an infrared spectrograph installed at the Calar Alto Observatory at 2.1 km altitude in southern Spain.
GJ 3512 Planetary System
The star (red dwarf) named GJ 3512 contains only 10% of the total mass of the Sun. Despite its low mass, the star is being orbited by a massive planet.
According to current theoretical models, such small stars should only be orbited by planets the size of the Earth or at most 10 times more massive than the Earth. The planet detected in this case, however, has a mass nearly half as big as Jupiter.
This exoplanet (named GJ 3512b) lies 30 light-years away from Earth. It is at least twice more massive than the celestial bodies calculated by theoretical models for low-mass stars. More specifically, it has a minimum mass of 0.46 Jupiter mass and an eccentric 204-day orbit.
How it might have formed?
Observations show that GJ 3512 continuously moved toward and away from Earth. This happens when a companion has a large mass. The team analyzed the possible formation conditions for this mysterious exoplanet.
They modeled the evolution of planets which showed that numerous small planets can be formed around small stars. Trappist -1 is the perfect example of such a planetary system.
Unlike GJ 3512, Trappist-1 has 7 planets with masses less than or equal to the mass of the Earth. Most theoretical models agree with this observation, but that’s not the case with GJ 3512. The new model (the one developed in this study) also suggests that such small stars shouldn’t have giant planets.
The failure of the model, however, can be explained by the process of planet formation. Typically, planets are formed in a ‘bottom-up process’ in which their small bodies gradually grow into larger masses by acquiring dust grains in orbit around the central protostar.
GJ 3512b might have formed in a different scenario, a mechanism called gravitational collapse. In this case, the astronomical object collapses under its own gravity. Its matter is drawn inward toward the center of gravity. This can be referred to as a ‘top-down process’.
The explanation still has several problems. If the planet was massive enough to become unstable due to its own gravitational force, why didn’t it continue to grow and approach closer to the star?
In the near future, this discovery would help us better understand how planets are actually formed around such stars.