Key Takeaways:
- The formation mechanisms of widely separated binary star systems remain a topic of ongoing investigation, with various competing hypotheses under consideration.
- The Gaia satellite's precise measurements will contribute significantly to characterizing ultrawide binaries and elucidating their formation processes.
- The long-term stability of wide binaries is influenced by gravitational interactions with other stars in the galactic environment, leading to eventual breakup over extended timescales.
- While no definitive upper limit exists for binary star separations, the probability of observing such systems diminishes drastically as the separation increases, due to both formation challenges and susceptibility to disruption.
The second issue is better understood. If the two stars in a very wide binary were the only stars in the universe, the pairing could survive forever. But the universe is a busy place, and our Milky Way alone contains more than 100 billion stars moving around its center. A very wide binary has a very weak gravitational bond, so if another star passes near the binary, the pair can break apart. Eighty years ago, Armenian astronomer Victor Ambartsumian calculated that a wide binary rarely breaks apart as the result of a single close encounter with another star, but rather through numerous distant passages that each gently tug on the binary until it imperceptibly passes from being bound to being unbound.
For a very long time, the two stars will still travel together through space until eventually they part ways. An ultrawide binary with a separation of 0.5 parsec (1.6 light-years) is statistically likely to break up within just 100 million years, while a slightly less extreme binary with separation around 0.1 pc (0.3 light-years) may survive for more than 1 billion years.
In summary, there is no known fixed upper limit for binary separations, but the wider a binary is, the more difficult it will be to find.
