An incredibly bright star system that has long baffled astronomers could soon light up the sky with the nuclear brilliance of thousands of suns, a new study suggests. When this happens, the results will be visible from Earth with the naked eye – day or night.
The star system, called V Sagittae, consists of a white dwarf – the dense core of a dead star similar to the Sun – and a more massive stellar companion located about 10,000 light-years away in the constellation Sagittarius. The voracious white dwarf is gobbling up material from its companion “at a rate never seen before,” the team said in a report. statement.
“Matter accumulated on the white dwarf will likely lead to a nova explosion in the coming years, during which V Sagittae will become visible to the naked eye,” Pablo Rodriguez-Gilprofessor at the Institute of Astrophysics of the Canary Islands in Spain and co-author of the study, the statement said.
Understanding the Beast
In a study published in November in the journal Monthly Notices of the Royal Astronomical SocietyAn international research team led by the University of Turku in Finland analyzed the light emitted by V Sagittae to better understand what exactly this beast is.
The data were collected over a 120-day observing period using the X-Shooter spectrograph on the European Southern Observatory's Very Large Telescope, located at 8,600 feet (2,600 meters) atop Mount Paranal in Chile's Atacama Desert.
Spectrographs such as the X-Shooter collect incoming light from celestial objects and then separate that light into its component wavelengths. This provides a spectrum that reveals the chemical composition of an object as each atom and molecule absorbs and reflects light of a specific wavelength. For perspective, imagine a prism splitting white light into its component colors, creating a rainbow.
These spectral data helped the researchers reanalyze the characteristics of V Sagittae. Previously, in a 1965 study, astronomers calculated that the two stars had solar masses of 0.7 and 2.8, although this conclusion is controversial.
To constrain the size of the stars, this later study took into account factors such as the orbital period to suggest that the entire system may have a mass below 2.1 solar masses, with each of the white dwarfs and its companions weighing about 1 solar mass.
Phil CharlesEmeritus Professor of Astronomy at the University of Southampton and co-author of the study, described the confusion surrounding this “very important system”. The uncertainty stems from the complex, constantly changing light emission of V Sagittae, which is “most likely due to the rapid outflow of light” rather than the orbital motion of the stars, making it difficult to determine their size.
“The results of our study show that no one has yet been able to unambiguously determine the orbital motion of each component, and therefore we do not yet have a reliable measurement of the mass of each star.” Charles told Live Science via email.
Orbital nuclear bomb
The researchers also identified V Sagittae as a super-soft X-ray source (SSS), meaning it produces lower-energy X-rays compared to hard sources such as an active X-ray source. black holes and colliding neutron stars. Classic SSSs consist of an accreting white dwarf and a more massive star whose gas spills out and falls onto the white dwarf.
V Sagittae's prodigious gravitational appetite drives a sustained thermonuclear reaction on the white dwarf's surface, turning it into an orbital nuclear bomb and the brightest SSS in the galaxy, the researchers said in their report. statement.
In fact, even during its fainter phases, V Sagittae is 100 times brighter than other variable star systems. The rate at which material in the white dwarf's accretion disk is falling changes dramatically and unpredictably, sometimes in just a few days, as it struggles to absorb all the material it steals from its partner, the team said in a separate report. statement.
As a result, a significant amount of material leaked out and formed a ring or halo of gas that surrounds both stars, forming a “circular disk” with a radius that could span about two to four times the distance between the two stars.
Daytime supernova
V Saggitae's chaotic accretion and extreme brightness are signs of its imminent violent death, which will be preceded by an explosive appetizer, so to speak, offering a promising scenario for hopeful stargazers: a nova explosion.
New stars form when an accreting white dwarf star absorbs too much material and then explosively ejects it from its surface. These stellar explosions do not destroy their white dwarfs, but they are nonetheless stunning: the middle nova is shining. hundreds of thousands of times bright as the sun. Because they do not destroy their white dwarfs, these novae can appear again after thousands or millions of years.
However, this exciting spectacle will only be a prelude to the main event. As the stars spiral into each other and collide with each other, they will produce “a supernova explosion so bright that it can be seen from Earth even during daylight,” Rodriguez-Gil adds.
This ultimately brilliant ending may happen already in 2067according to a 2020 study from Louisiana State University that predicted the demise of V Saggitae based on the decreasing orbital period of its stars. Charles concludes that if “[observed] the period of decline continues, then this must happen, but stellar evolution is difficult to predict accurately, so things can easily change!”
So keep an eye out Arrow in search of a nova and mark your calendar for a supernova that will spectacularly mark the end of one of our galaxy's most tantalizing star systems.
