Using the Atacama Large Millimeter/submillimeter Array (ALMA), astronomers have found a possible “sibling” of a planet orbiting a distant star. The team found a cloud of debris that may be sharing the planet’s orbit, which they believe could be the building blocks of a new planet or the remnants of one that has already formed. If confirmed, this discovery would be the strongest evidence yet that two exoplanets could share an orbit.
“Two decades ago the theory predicted that pairs of planets of the same mass could have the same orbit around their star, the so-called Trojan or co-orbital planets. For the first time, found- We have evidence in favor of that idea,” said Olga Balsalobre-Ruza, a student at the Center for Astrobiology in Madrid, Spain who led the paper published today in Astronomy and Astrophysics.
Trojans, rocky bodies in the same orbit as a planet, are common in our own solar system, the most famous example being Jupiter’s Trojan asteroids—over 12,000 rocky bodies in the same orbit around the sun in a gas giant. Astronomers have predicted that Trojans, especially Trojan planets, may also exist around a star other than our sun, but there is little evidence for them.
“Exotrojans [Trojan planets outside the solar system] until now like unicorns: They were allowed to exist by theory but no one noticed it,” said co-author Jorge Lillo-Box, a senior researcher at the Center for Astrobiology.
Now, an international team of scientists has used ALMA, of which ESO is a partner, to find the strongest observational evidence that Trojan planets can exist—in the PDS 70 system. This young star is known to host two giant Jupiter-like planets, PDS 70b and PDS 70c. By analyzing archival ALMA observations of this system, the team found a cloud of debris at the location of PDS 70b’s orbit where the Trojans were expected to be.
The Trojans occupy the so-called Lagrangian zones, two extended regions in a planet’s orbit where the combined gravitational pull of the star and the planet can trap material. Studying these two regions in the orbit of PDS 70b, astronomers detected a faint signal from one of them, indicating that a cloud of debris with a mass almost twice that of our moon could reside. there.
The team believes that this cloud of debris could point to an existing Trojan world in this system, or a planet in the process of formation. “Who can imagine two worlds that share the length of the year and the conditions of the habitat? Our work is the first evidence that this kind of world can exist,” said Balsalobre-Ruza. “We can imagine that a planet can share its orbit with thousands of asteroids as in the case of Jupiter, but it surprises me that planets can share the same orbit.”
“Our research is a first step in finding co-orbital planets early in their formation,” said co-author Nuria Huélamo, a senior researcher at the Center for Astrobiology. “This opens up new questions about the formation of Trojans, how they evolve and how frequent they are in different planetary systems,” added Itziar De Gregorio-Monsalvo, ESO’s Head of the Office for Science in Chile, which also contributed to this research.
To fully confirm their detection, the team will have to wait until after 2026, when they intend to use ALMA to see if PDS 70b and its sister debris cloud are moving significantly in their orbit. together around the star. “This is a breakthrough in the exoplanetary field,” said Balsalobre-Ruza.
“The future of this topic is very exciting and we look forward to the expanded capabilities of ALMA, planned for 2030, which will greatly improve the array’s ability to detect Trojans among many other stars,” concluded De Gregorio-Monsalvo.
O. Balsalobre-Ruza et al, Tentative co-orbital submillimeter emission within the Lagrangian region L5 of the protoplanet PDS 70 b, Astronomy and Astrophysics (2023). DOI: 10.1051/0004-6361/202346493
Citation: Does this exoplanet have a ‘sibling’ that shares the same orbit? (2023, July 19) retrieved 19 July 2023 from https://phys.org/news/2023-07-exoplanet-sibling-orbit.html
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