In our last episode, we brought you the news that the Gaia mission had increased the number of known binary star systems in our galaxy from 300,000 to 800,000. How all those stars formed — we have part of that answer today.
In many, and perhaps most, cases, these two-star systems formed when a collapsing cloud of gas fragments into two orbiting pieces. Each cloud fragment will form its own star, but these objects will end up gravitationally bound together as they orbit the galaxy. These systems can end up with planets around each individual star or orbiting both stars, allowing for us to imagine a real-life double sunset like Luke watched on Tatooine.
We also know that in the eldest globular clusters, stars can pass so closely together that they can gravitationally grab onto one another, creating new binary systems, and sometimes even merging into new stars.
In birth, and in death, binaries come together.
But a new paper coming out in The Astrophysical Journal shows us that just like people can have found family early in life, so too can stars.
Observers looking at the young star L483 expected to find a single star with a single well-behaved magnetic field that aligned with the star’s inflowing gas. At the largest scales, this is exactly what was seen, but in higher detailed images taken with the SOFIA Airborne Observatory, kinks in the magnetic field were revealed, and with them, a hidden companion star. According to lead researcher Erin Cox: We think these stars formed far apart, and one moved closer to the other to form a binary. When the star traveled closer to its sibling, it shifted the dynamics of the cloud to twist its magnetic field. … We don’t know why one star would move toward another one, but we think the moving star shifted the dynamics of the system to twist the magnetic field.
Found family, y’all. That second star? It was hungry and needed a home and found one by snuggling up next to an adopted sibling. Separated by about the same distance as the Sun and Pluto, these two stars are now growing up together, consuming material in a shared stellar nebula. Time will tell if they go on to share planets and solar systems.
Northwestern press release
“The Twisted Magnetic Field of the Protobinary L483,” Erin G. Cox et al., 2022 June 13, The Astrophysical Journal