This super-bright star could be the next naked-eye supernova visible from Earth
An incredibly bright star system that has long baffled astronomers could soon light up the sky with the nuclear glow of thousands of suns, new research suggests. When this happens, the results can be visible from Earth with the naked eye, day or night.
The star system, called V Sagittae, is made up of a white dwarf – the dense core of a dead sun-like star – and a more massive stellar companion, located about 10,000 light-years away, in the constellation Sagitta, the Spire. The voracious white dwarf gorges itself on material from its companion “at a rate never before seen,” the team said in a statement. statement.
“Material accumulated on the white dwarf is likely to produce a nova explosion in the coming years, during which V Sagittae would become visible to the naked eye,” Pablo Rodriguez-Gilprofessor at the Canary Islands Institute of Astrophysics in Spain and co-author of the study, said in a statement.
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 exactly what type of beast it is.
These data were collected over a 120-day observation period by the X-Shooter spectrograph on the European Southern Observatory’s Very Large Telescope, located at an altitude of 8,600 feet (2,600 meters) atop Cerro Paranal in Chile’s Atacama Desert.
Spectrographs like X-Shooter collect incoming light from celestial objects, then separate that light into its constituent wavelengths. This provides a spectrum that reveals the chemical composition of the object, since each atom and molecule absorbs and reflects a certain wavelength of light. To take a step back, think of how a prism divides white light into its constituent colors to produce a rainbow.
These spectral data helped researchers reanalyze the characteristics of V Sagittae. Previously, in a 1965 study, astronomers calculated that its two stars measured 0.7 and 2.8 solar masses, although this conclusion is controversial.
To limit the size of the stars, this more recent study took into account factors such as orbital period to suggest that the entire system could be smaller than 2.1 solar masses, with the white dwarf and its companion each 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 arises from V Sagittae’s complex and constantly fluctuating light emissions, which are “more likely due to rapid fluxes” rather than the stars’ orbital motions, making it difficult to determine their size.
“Our study shows that no one has yet been able to uniquely identify the orbital motion of each component and so we do not yet have a good measure of the mass of each star.” Charles told Live Science via email.
A nuclear bomb in orbit
The researchers also identified V Sagittae as an ultra-soft X-ray (SSS) source, meaning it generates lower-energy X-rays compared to hard sources like active X-rays. black holes and colliding neutron stars. Classical SSSs are composed of an accreting white dwarf and a more massive star whose gas overflows and falls onto the white dwarf.
V Sagittae’s prodigious gravitational appetite causes a sustained thermonuclear reaction on the white dwarf’s surface, transforming it into an orbiting nuclear bomb and the brightest SSS in the galaxy, researchers said in a statement. statement.
In fact, even during its faintest phases, V Sagittae is 100 times brighter than other variable star systems. The speed of material entering the white dwarf’s accretion disk changes dramatically and unpredictably, sometimes within just a few days, as it struggles to consume all the matter it steals from its partner, the team said in another statement. statement.
As a result, a significant amount of material escaped and formed a ring, or halo, of gas that surrounds the two stars, composing a “circumbinary disk” whose radius can extend approximately two to four times the distance between the two stars.
A daytime supernova
The chaotic accretion and extreme luminosity of V Saggitae are signs of its imminent and violent death, which will be preceded by an explosive appetizer, so to speak, offering a promising scenario for hopeful astronomers: a nova explosion.
Novae occur when an accreting white dwarf engulfs too much material and then explosively ejects it from its surface. These stellar explosions do not destroy their white dwarfs but are nonetheless stunning, with the average nova shining hundreds of thousands of times as bright as the sun. Since they do not destroy their white dwarfs, these novae can reproduce over thousands or even millions of years.
But this spectacular show will only be a prelude to the main event. When stars collide and collide, they produce a “supernova explosion so bright that it will be visible from Earth even during the day,” Rodríguez-Gil adds.
This ultimately brilliant finale could happen from 2067according to a 2020 study from Louisiana State University, which predicted the demise of V Saggitae based on the decreasing orbital period of its stars. Charles concludes that if the “[observed] period decline continues, so it must be happening, but stellar evolution is hard to predict exactly, so it could easily change!”
So keep an eye out Sagittarius for a nova and mark your calendars for the supernova that will spectacularly spell the end of one of the most tantalizing star systems in our galaxy.
