Scientists have long speculated about the possibility of two planets sharing the same orbit, and now a new image captured by the ALMA telescope in Chile provides evidence to support this theory. Released by the European Southern Observatory on July 19, 2023, the image shows what appears to be two planets, or at least objects in orbit, around a star called PDS 70.
The image reveals a large golden disk of material from which the planets are believed to be forming, with the star located at the center of the ring. One of the objects in orbit, known as PDS 70b, has been confirmed as a planet. The second object, situated next to the disk at the 3 o’clock position, is still uncertain, with scientists speculating that it could be a cloud of debris or the building block remnants of a planet.
Lead author Olga Balsalobre-Ruza from the Center for Astrobiology in Madrid, Spain, expressed their excitement, stating that this finding provides evidence in favor of the idea that two planets of similar mass can share the same orbit, known as Trojan or co-orbital planets. She added that the discovery is groundbreaking, as it challenges the existing notion of a planet sharing its orbit with thousands of asteroids.
The presence of Trojan asteroids orbiting within the same path as planets is not unique to our own solar system. For example, the Trojan asteroids of Jupiter are situated both in front of and behind the gas giant. Earth also has its own Trojan asteroids. Although theory allowed for the existence of similar objects in other solar systems, no concrete evidence had been found until now.
To search for exo-Trojans around the PDS 70 star, a team of international scientists utilized archival data from ALMA. PDS 70 is a young star known to have two Jupiter-like planets, PDS 70b and PDS 70c. The team observed a cloud of debris within the orbit of PDS 70b, precisely where Trojan objects would be expected to exist.
There are stable regions in a planet’s orbit called Lagrange points 4 and 5, which lead and follow the planet, respectively. These regions allow material to accumulate due to the gravitational forces exerted by the star and the planet. In one of PDS 70b’s Lagrange zones, the researchers discovered a cloud of debris with a mass equivalent to two Earth moons. This finding suggests the presence of an existing Trojan world or one in the process of formation.
The possibilities presented by the existence of sibling planets sharing an orbit are intriguing. The researchers referred to these potential sibling planets as Trojan planets or co-orbital planets. Confirmation of their presence can only be obtained in 2026 when ALMA will capture their orbital movement. The extended capabilities planned for ALMA in 2030 are predicted to significantly enhance the array’s ability to study Trojans in various star systems.
Nuria Huélamo, another researcher from the Center for Astrobiology, viewed this research as the initial step in identifying co-orbital planets during the early stages of their formation. Itziar de Gregorio-Monsalvo from ESO expressed excitement about future possibilities and the ability to explore the formation, evolution, and prevalence of Trojans in different planetary systems.
In conclusion, the recently captured image offers promising evidence supporting the idea that two planets can share an orbit. This discovery challenges our previous understanding and opens up new avenues of research. While confirmation is still pending, the potential in this field of study is highly promising. The scientific community eagerly awaits the future findings of the extended ALMA capabilities, which could revolutionize our understanding of co-orbital planets and their prevalence in the universe.
