Astronomers Detect First Evidence of 'Sibling' Planets Sharing Same Orbit

Astronomers using one of Earth's most powerful telescopes have spotted something that shouldn't exist—or at least, something that has never been seen beyond our own solar system. In a planetary system 370 light-years away, they found a cloud of dust and debris orbiting a star in the exact same path as a giant exoplanet, suggesting that two worlds might be sharing the same orbital route around their sun.

The discovery centers on the PDS 70 system, home to two Jupiter-sized planets called PDS 70b and PDS 70c. Using the Atacama Large Millimeter/submillimeter Array, or ALMA, researchers detected a concentration of material at a gravitationally stable point in PDS 70b's orbit—a region where objects can naturally accumulate and remain trapped by the combined pull of the star and planet. This zone, known as a Lagrangian point, is where astronomers theoretically expect such co-orbital companions to form. The dust cloud contains roughly twice the mass of Earth's moon and orbits about 14 times farther from PDS 70b than Earth sits from the sun.

In our own solar system, such objects are commonplace. Jupiter hosts more than 12,000 of these co-orbital companions, known as Trojans, along with thousands more scattered throughout the orbits of Mars, Uranus, Neptune, and even Earth. Yet despite their abundance here at home, no one has ever confirmed their existence around a distant star until now. The largest Trojan in our solar system, an asteroid called Hektor, measures just 220 kilometers across—far smaller than what the researchers believe they may have found near PDS 70b.

What makes this discovery particularly striking is its timing. The two planets in the PDS 70 system are young, still in their formative stages, which means astronomers are potentially witnessing the birth of a Trojan in real time. The dust cloud could represent the building blocks of a planet yet to coalesce, or it could be the remnants of a world already formed. Olga Balsalobre-Ruza, a researcher at the Centre for Astrobiology in Madrid, and her colleagues describe these objects as fossils of planetary formation—windows into how solar systems assemble themselves. They also note that such worlds could theoretically be habitable and might play a role in the formation of large moons.

The researchers emphasize that what they have found is strong circumstantial evidence, not definitive proof. The dust accumulation sits precisely where theory predicts Trojans should exist, and it shares the orbital path of PDS 70b, but current observations cannot determine whether this cloud will eventually become a planet, whether it already is one, or whether it represents something else entirely. The team will need to wait until 2026 to conduct follow-up observations with ALMA that could track whether the planet and debris cloud move together through space, which would confirm they truly share an orbit.

If confirmed, the finding would reshape how astronomers understand planetary systems. It would mean that worlds need not orbit alone—that planets can share their year with thousands of companions, just as Jupiter does, or potentially with other planets. The prospect of two full-sized worlds occupying the same orbital path, with the same orbital period and potentially similar conditions for life, strikes researchers as almost incomprehensible given what we know from our own neighborhood. Yet the evidence, still preliminary but compelling, suggests that somewhere in the constellation Centaurus, such a configuration may already exist.