In a solar system far, far away, astronomers have discovered evidence of possible "sibling" planets sharing the same orbit.
The researchers detected a cloud of debris in the same orbital path as an exoplanet around a star roughly 400 light-years away using the Atacama Large Millimeter/submillimeter Array (ALMA), leading them to suspect that it may be the remnants of a planet, or a planet yet to be formed, a study published in the journal Astronomy and Astrophysics reveals.
Objects sharing the same orbit as a planet are known as Trojans. Our solar system is home to thousands of these objects, many of which are asteroids sharing Jupiter's orbit, but until now, none have been detected outside of our own solar system.
"We have found for the first time strong evidence of the formation of Trojans in other planetary system," Olga Balsalobre-Ruza, a student at the Centre for Astrobiology in Madrid, Spain, and Itziar De Gregorio-Monsalvo, head of the Office for Science at European Southern Observatory (ESO) Chile, both co-authors of the paper, told Newsweek.
"In particular, using data from the Atacama Large Millimeter Array (ALMA) telescope we have found a cloud of debris sharing the same orbit of a forming giant planet, PDS 70b. That cloud of dust could build in the future or already contain a young exotrojan."
The astronomers made this discovery in the PDS 70 system, 370 light-years away, which hosts two large, Jupiter-like planets called PDS 70b and PDS 70c. They found the cloud of debris at a point in PDS 70b's orbit where Trojans are expected to exist, called the Lagrangian zone.
"Exotrojans are bodies that can be formed naturally inside the dust clouds trapped in the so-called Lagrangian zones, where the combined gravitational pull of the star and the planet can trap material," Balsalobre-Ruza and De Gregorio-Monsalvo said.
"We think this is the case since the cloud falls in the Lagrangian point L5 of the planet. These objects are very interesting since they are 'fossils' of the planetary formation processes, they are potential habitable worlds, and they can intervene in the formation of large moons."
The cloud is thought to have a mass of up to two times that of Earth's moon and is around 14 times further away from PDS 70b than the sun is from Earth. While this finding is not a definitive Trojan, it's the closest evidence astronomers have so far.
"This is the first time we search for them accompanying young planets (the only two young planets confirmed are in this system, PDS 70b & c), where their Trojans can be forming at the present time," the researchers said.
"We found evidence of accumulation of dust of up to two times de mass of our moon in the expected location, i.e., inside the orbit of the planet PDS 70b and in the Lagrangian region L5, where Trojans are expected to be formed."
In our own solar system, Trojans can be found not only in Jupiter's orbit, but also in the orbits of Mars, Uranus, Neptune, and even Earth.
"In the Solar System Trojan asteroids are very common. The Earth (with two of them detected so far), Mars, Jupiter, Uranus and Neptune have co-orbital companions," Balsalobre-Ruza and De Gregorio-Monsalvo said.
"Jupiter, is the planet with the vast majority of Trojans, with more than 12,000 distributed in L4 and L5. Nonetheless, all of them are very small in comparison with what we are searching for. The largest in the Solar System, (624) Hektor is just 220 km (136 miles) sized."
Our solar system doesn't have any Trojans as large as this exoplanet may be. More research will be needed to figure out if this cloud truly is a Trojan, and if it is the result of a proto-planet or the remnants of one.
"Unfortunately we do not have the power to see that level of detail with our observations, and the only thing we can say is that there is a dust accumulation that could be the building block of a future new planet or the remnant of a co-orbital planet that is already formed," they said.
The researchers will have to wait until 2026 to confirm their finding is indeed a Trojan, using ALMA to see if the planet PDS 70b and the cloud of debris appear to move along the same orbital path.
"This would be a breakthrough in the exoplanetary field," Balsalobre-Ruza said in a statement. "Who could imagine two worlds that share the duration of the year and the habitability conditions? We can imagine that a planet can share its orbit with thousands of asteroids as in the case of Jupiter, but it is mind-blowing to me that planets could share the same orbit."
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Jess Thomson is a Newsweek Science Reporter based in London UK. Her focus is reporting on science, technology and healthcare. ... Read more
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