The solar system has always been known for its organization and order. Each planet orbits its own orbit at a certain distance from the Sun. However, recent research allows us to ponder the possibility of planets that share the same orbit. This discovery may change the way we think about the formation and evolution of planetary systems.
Researchers looked at a young planetary system called PDS-70, which is about 370 light-years away from Earth. In this system, something has been discovered that could be a Trojan planet, an object that shares an orbit with the already known exoplanet PDS-70b. According to preliminary calculations, the mass of this object is twice the mass of Earth’s Moon.
Trojan planets, or exotrojans, are worlds that are in the same orbit as a larger planet and are at gravitationally stable points along its orbit. These are the so-called Lagrange points or Lagrangians. Each two-body system has five such points where the gravitational interaction between them is balanced by the centripetal force. Points L4 and L5 are on the orbit of the smaller body, and points L1, L2 and L3 are on the line connecting the two bodies.
Such Lagrange points are special regions in space where matter can collect and exist in relative stability. For example, Jupiter collects asteroids at its L4 and L5 points, which are known as Trojan asteroids. Even Earth has a couple of Trojan asteroids. Such points are also good locations for space observatories.
The discovery of a possible Trojan planet in the PDS-70 system is of great interest to scientists. After all, it is the first evidence for the existence of planets that share the same orbit. This could have important implications for our understanding of the formation and evolution of planetary systems.
Astrophysicist Olga Balsalobre-Ruza of the Center for Astrobiology in Spain notes that this possibility was previously predicted theoretically, but only now have we discovered the first evidence for the idea. She also notes that this may be the first step toward understanding how planets form and evolve.
For now, the orbital partner of exoplanet PDS-70b is thought to be a thick cloud of dust, which is the building material for a future planet. This may help scientists understand the formation process of exotrojans and planetary systems in general.
Interestingly, studying the PDS-70 system may also shed light on the theory of planet migration. Jupiter is believed to have collected its Trojans over time and migrated from a farther point from the Sun. Studying PDS-70b, which is similar to Jupiter, may help confirm or deny this theory.
However, to get more definitive answers, scientists will have to wait until 2026, when they can study the system again and see if the possible Trojan planet moves with PDS-70b as a co-orbital companion in the L5 Lagrangian.