Astronomers utilizing the Atacama Large Millimeter/submillimeter Array (ALMA) have captured a rare celestial event: the formation of a massive binary star system from two distinct stars that merged just approximately 60 years ago. This discovery challenges the prevailing assumption that most binary stars originate from the fragmentation of a single collapsing cloud of gas and dust.
The research focuses on IRAS 07299−1651, a binary system located roughly 5,300 light-years away. Initial observations conducted in 2019 detected misaligned disks of material surrounding the two growing protostars, hinting that they did not share a common origin. Over an eight-year period, scientists combined data from ALMA, the Very Large Array (VLA), the James Webb Space Telescope (JWST), and the Very Large Telescope (VLT) to map subtle positional shifts and reconstruct the system’s three-dimensional structure.
“For the first time, we were able to watch two massive stars move around one another while they were still being born,” said Yichen Zhang of Shanghai Jiao Tong University, who led the team. “Each telescope revealed a different piece of the puzzle,” added Rubén Fedriani of the Instituto de Astrofísica de Andalucía. “The combination of radio and infrared observations provides the most exquisite detail on the formation of this massive protobinary system.”
The study yielded unexpected results. Rather than moving in neat, circular orbits, the stars follow highly eccentric, almost parabolic paths. Their individual disks are tilted at sharp angles relative to each other and their orbits, a configuration difficult to explain if the stars formed from the same natal disk.
Researchers theorize that the two stars were born in separate clouds of gas and dust before a chance gravitational encounter brought them together. By tracing their orbital histories, the team calculated that this collision occurred roughly 60 years ago—a fleeting moment on cosmic timescales. Despite the chaos of the merger, the disk-shaped pockets of material around each star have retained their structural integrity.
“It felt like solving a three-dimensional puzzle,” said Yao Wang of Shanghai Jiao Tong University. “Each new observation added another piece, and eventually the orbit, disks, and jets all came together into a single, coherent picture.”
Jonathan C. Tan of the University of Technology and the University of Virginia noted, “This study demonstrates that the early lives of stars can be quite chaotic, with a chance encounter leading to this gravitational dance and stellar coupling.”
The ultimate fate of IRAS 07299−1651 remains uncertain. It is unclear whether the stars will remain bound or eventually drift apart, a process that may be influenced by interactions with surrounding gas. Scientists hope continued monitoring will clarify this outcome and provide insights into how common such chaotic formation events are across the galaxy. The findings were published on September 8 in the journal Nature Astronomy.
This really rewrites the textbook on star formation. I always assumed binary pairs were born together, not glued by chaos.
Sixty years is a blink of an eye astronomically. The idea we watched this happen in real time is genuinely mind-blowing.