Team sees possible exoplanet sharing orbit with another – 08/13/2023 – Sidereal Messenger

Imagine Earth had a neighboring planet sharing the same orbit, taking the same time to complete revolutions around the Sun. Maybe life forms appeared there at the same time as here, preserving a biosphere for billions of years. This idea, which looks more like a science fiction premise, obviously does not correspond to reality in the Solar System. But our understanding of the process that leads to the formation of planets suggests that possibly this could have happened elsewhere in the Universe, and now an international group of astronomers has found the strongest evidence that, somewhere in the cosmos, these so-called co-orbital planets.

The result, published in an article in the journal Astronomy & Astrophysics, explores the star cataloged as PDS 70, located 370 light-years from here and important because it is the only young planetary system (5.4 million years old), still in the process of formation, which is known to host two protoplanets, amid the gas and dust disk that surrounds the star. For us, in Brazil, its importance has a special taste, because its star was characterized by a scan carried out at the Pico dos Dias Observatory, in Brazópolis, Minas Gerais (PDS is an acronym for Pico dos Dias Survey).

The first author of the work was Olga Balsalobre-Ruza, from the Center for Astrobiology, in Madrid, Spain, and consisted of a reanalysis of observations obtained by the Alma radio telescope array, located in the Chilean Andes, in 2019. The ambition was to find evidence of the so-called Trojans in the orbit of the two giant planets in formation there. Trojans are asteroids that accumulate in two points along the orbit of a planet (separated by 60 degrees from it) where the gravity of the system favors their presence. The first ones were discovered in the orbit of Jupiter and got that name because they were initially named after heroes of the mythical Trojan War.

When analyzing the data, the group found what appears to be an accumulation of dust at one of the points around 60 degrees on the protoplanet PDS 70 b, the innermost of the two known. This material, estimated to have up to twice the mass of the Moon, could be the precursor to a co-orbital planet or perhaps even the remnants of one’s formation. The team hopes to carry out further observations with Alma starting in 2026 (allowing enough time for the planet and the dust cloud to move in their orbit) in order to confirm the discovery and refine their characterization. It’s not a daydream to imagine that we might be on the verge of discovering a planet that shares its orbit with another. And this is just the latest of the expectations created by the study of the PDS 70 system.

Earlier, using the same Alma observations, another group of astronomers found evidence that the protoplanet PDS 70 c has a circumplanetary, moon-forming disk. And more recently, late last month, a team using the James Webb Space Telescope detected the presence of water vapor in the innermost region of the system, where rocky planets – like Earth – may be forming. In many ways, studying it is a bit like seeing how our own Solar System came to be.

This column is published on Mondays in the printed version, in Folha Corrida.

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