These planetary twins, previously only a theoretical concept, have now been found for the first time, according to astronomers.
“Who could have imagined the existence of two planets with the same year length and habitable conditions,” said Olga Balsalobre-Ruza, a researcher at the Center for Cosmic Biology in Madrid, Spain, who led the study. “Our work provides the first evidence that such a world type could exist.”
The star system in question is called PDS 70, located in the Centaurus constellation and situated 370 light-years away from the Solar System. Its two planets, PDS 70b and PDS 70c, are Earth-sized and share the same orbital path around the star in a peculiar phenomenon known as “Trojan planets.” However, astronomers also detected a dust cloud in the orbit of PDS 70b, possibly indicating the formation of a new planet.
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The image of the PDS 70 planetary system was captured by the ALMA astronomical telescope. At the center is a star, and orbiting around it are two planets.
Scientists believe that direct imagery serves as the most compelling evidence for the possibility of two planets sharing the same orbit.
“Two decades ago, we predicted that two planets with the same mass could share the same orbit around their star, known as Trojan planets or co-orbital planets. This is the first time we’ve discovered evidence to support this idea,” said researcher Olga Balsalobre-Ruza.
Trojans are rocky bodies with the same orbital path as planets. This phenomenon is relatively common in the Solar System, including two Trojan asteroids accompanying Earth, as well as over 12,000 Trojan asteroids existing in the orbit of Mars as it revolves around the Sun. NASA’s Lucy spacecraft, launched in October 2021, will be the first spacecraft to study these never-before-seen asteroids up close.
However, evidence of Trojan planets outside the Solar System is relatively scarce.
“They exist theoretically, but no one has discovered them yet,” stated Jorge Lillo-Box, co-author of the research and a researcher at the Center for Cosmic Biology.
This discovery raises questions about how Trojans form and evolve and the prevalence of Trojan planets in other systems, said Itziar De Gregorio-Monsalvo, co-author of the study and head of the Science Office in Chile at the Southern European Observatory.
The exoplanet PDS 70b, discovered in 2018, has a mass three times that of Earth and takes over 119 years to complete its orbit around its star.