Using the Atacama Large Millimeter/submillimeter Array (ALMA), astronomers have captured one of the most detailed three-dimensional views yet of a massive binary star system still in the process of forming. By tracking the movements of two young, massive stars over nearly eight years, the team discovered that the pair follows a highly stretched-out orbit and is surrounded by gas disks that are tilted relative to each other and to the stars’ orbit. The findings, published in the journal Nature Astronomy, suggest that the two stars did not form together from a single spinning disk of material, as is often assumed, but instead formed separately and later came together through a close gravitational encounter. This discovery reveals a new possible way that close massive binary star systems may form. Most massive stars are born with a companion, and at least 90% are thought to exist in binary or multiple systems. These massive binaries have a significant impact on their surroundings, influencing the formation of new stars and the distribution of heavy elements through supernova explosions. However, because most known massive binaries are studied long after they have finished forming, astronomers have had limited opportunities to observe the actual moment of their assembly. To change this, an international team led by Yichen Zhang of Shanghai Jiao Tong University studied IRAS 07299−1651, a system containing two massive protostars—stars still growing by pulling in surrounding gas and dust. The team had previously studied this system in 2019, when ALMA observations provided initial insights into the pair’s dynamics. At the time, the results seemed to align with the standard theory that two stars form together from the fragmentation of a single large disk. However, one detail stood out: the disks around the two stars were already misaligned. To investigate further, the researchers spent nearly eight years tracking extremely subtle shifts in the stars’ positions in the sky. This technique requires high precision and is well within ALMA’s capabilities. The team combined these long-term observations with data from the U.S. National Science Foundation's Very Large Array (VLA), as well as infrared images from the James Webb Space Telescope (JWST) and ESO's Very Large Telescope (VLT), which revealed jets of material streaming away from the young stars. Using this data, the team reconstructed the system’s three-dimensional structure for the first time, revealing how the stars orbit each other, how their disks are tilted, and how their jets point into space. Their findings were surprising. Instead of a circular orbit, the stars follow a highly eccentric, almost parabolic path. Their surrounding disks are tilted at a sharp angle to each other and to the orbit itself. This mismatched configuration is difficult to explain if the stars formed together in the same disk, where they would be expected to have aligned spins. Instead, the evidence points to an alternative origin: the two stars likely formed separately in their own pockets of gas before a chance close encounter brought them together while still enshrouded in their birth cloud. The current compact disks appear to have survived this encounter, maintaining their rotational structures. However, it is still unclear whether the stars will remain gravitationally bound. Their current motion is close to the threshold between a stable orbit and one that could eventually separate. Future observations will help determine their fate. More broadly, this study opens a new avenue for understanding how massive binary stars come together, and by applying similar long-term monitoring to other young systems, astronomers hope to uncover how often such close encounters, rather than shared formation in a single disk, build the massive binary systems observed across our galaxy.