Decades-Old Star Jet Theory Finally Confirmed in R Aquarii System

Astronomers have confirmed a decades-old theory about how jets form in the binary star system R Aquarii. New observations show that these powerful outflows occur when the two stars orbit closest to each other, a phenomenon known as periastron. The findings, published in Astronomy & Astrophysics, relied on high-resolution imaging from the Gemini South Telescope in Chile.

The R Aquarii system pairs a red giant and a white dwarf in a roughly 40-year orbit. When they reach their nearest point—called periastron—the white dwarf pulls far more material from the red giant. This surge of matter forms a spinning accretion disk around the white dwarf.

Using speckle imaging, the Tartu Observatory team captured details that would normally blur together. Their data revealed that some of the excess material in the disk is blasted outward in narrow, cone-shaped jets, one on each side, perpendicular to the disk.

This discovery aligns with a hypothesis first proposed in the 1980s by Wallerstein and others. Earlier studies from the 1970s had noted high-speed outflows and bipolar ejections in the system. Recent ALMA imaging in 2024 further supported the idea by showing how the jets precess and stay tightly focused.

The latest observations pinpointed the exact moment of ejection: when the stars were at their closest. This confirms the long-standing link between periastron and jet formation.

The study settles a long-debated question about R Aquarii's behaviour. By matching theory with direct observation, it shows how orbital mechanics drive the system's dramatic outflows. The results also highlight the value of advanced imaging in uncovering hidden details of cosmic interactions.