Astronomers have been monitoring V Sagittae for over a century, a binary system whose evolution challenges classical models. Its brightness variations and unstable behavior make it a privileged object of study for understanding the final stages of stellar life.
A pair of stars in extreme interaction
V Sagittae consists of a massive star and a white dwarf, connected by a very tight orbit of just 12 hours. The constant approach of the two celestial bodies fuels an unprecedented matter transfer due to its intensity.
The binary system V Sagittae, located about 10,000 light-years from Earth, shines brightly.
The white dwarf attracts matter from its companion, which accumulates on its surface and triggers violent thermonuclear reactions. This activity explains the system's extreme brightness, far superior to that of other known binaries.
Researchers are currently observing increasing instability in this gravitational dance. The rapid brightness oscillations suggest that the current equilibrium is precarious and that a major upheaval is imminent.
A revealing gas halo
Using the Very Large Telescope of the European Southern Observatory, astronomers have revealed a ring of gas surrounding both stars. This unexpected element provides a key to understanding the system's dynamics.
This halo results from the white dwarf's inability to absorb all the stripped matter. Some of it escapes, forming a bright envelope that betrays the phenomenon's intensity.
The existence of this structure challenges certain hypotheses about the evolution of binary systems. It suggests that similar interactions could play an important role in the end-of-life stages of many stars.
Towards a spectacular explosion
Specialists estimate that the accumulation of matter on the white dwarf could soon trigger a nova, making V Sagittae visible to the naked eye. This stage would be only a prelude.
In the longer term, the merger of the two stars seems inevitable. This collision should cause a supernova so intense that it would be observable in broad daylight from Earth.
Such an explosion, expected on a relatively short astronomical timescale, would provide a unique opportunity to directly study the violent death of an extreme binary system.
Article author: Cédric DEPOND