Tiina Liimets, an astronomer at the University of Tartu's Tartu Observatory, and her colleagues studied the symbiotic binary star R Aquarii located less than 15 light-years from Earth. Initially, the researchers aimed to use the Gemini South Telescope in Chile to refine the stars' orbital paths.

According to Liimets, however, the observed object wasn't in the expected location and the data was initially overlooked. "The object we found was actually farther away and at a different angle," Liimets explained. "We suspected we had made a mistake. We were so focused on what we expected to see that we couldn't recognize what was actually there."

Upon reanalysis, the researchers determined that the object in question was not a white dwarf, but rather a denser clump of matter within the jet, moving away from the system's central star.

Twin star symbiosis

The R Aquarii system consists of two stars at different stages of their life cycle: a red giant and a white dwarf. The red giant has expanded so much that its outer layers are only weakly bound by gravity, continuously shedding stellar wind. The white dwarf orbits the giant along an elliptical path, completing one full orbit approximately every 40 years.

When the stars reach the closest point in their orbit — called periastron — the transfer of mass from the red giant to the white dwarf increases significantly. As a result, an accretion disk forms around the white dwarf, which becomes unstable due to the excess inflow of matter.

Some of that material is ejected from the disk in a narrow, cone-shaped jet, perpendicular to the plane of the disk. Liimets explained that matter is expelled in a jet on both sides of the disk. "It's like water flowing from a faucet — this jet is just as narrow," the astronomer added.

Hypothesis confirmed

Astronomers have long suspected that jets of matter are formed specifically during periastron. Earlier technology, however, lacked the precision to observe this with sufficient resolution over the 40-year orbital cycle. The recent discovery confirmed that matter was indeed ejected from both sides of the accretion disk precisely at the moment when the two stars were closest to each other.

"This was the jet we've been searching for all this time," Liimets said. The finding is of particular scientific interest, as the connection between periastron and jet formation had never before been observationally confirmed. The research results were published in the journal Astronomy & Astrophysics.

The research team used the Gemini South Telescope in Chile, equipped with an 8.1-meter mirror, and employed speckle imaging — a technique that offers exceptionally high resolution. This technology makes it possible to distinguish details that would otherwise be missed or blurred together using conventional methods.

According to Tiina Liimets, the discovery serves as a broader lesson about scientific work. "You have to keep an open mind and not become fixated on what you think the data shows because there may be something else in there," the astronomer emphasized. Similar jet-like structures can be found throughout the universe appearing around both young stars and black holes at the centers of galaxies.

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