Recent spectroscopic analysis reveals that a hungry white dwarf and its solar-mass companion, enveloped in a giant gas disk and an extremely soft X-ray source, are on track to become a visible nova in the coming years and an extremely bright supernova in the 21st century.
The binary star system V Sagittae, about 10,000 light-years away in the constellation Sagitta, is making headlines again – and this time with a more detailed picture of what’s happening there now, and what’s expected to happen in the next century. It’s an exceptionally close pair of stars: a white dwarf – the dense core of a sun-like star that has ended its life – and a more massive companion, orbiting it in a cycle of just 12.3 hours. The white dwarf’s strong gravity is constantly sucking gas from the other star, creating a hot disk of falling material around it. This process makes V Sagittae one of the most extreme and intriguing systems in the Milky Way.
As we reported in a previous article in "The News" in September 2025, the white dwarf in this system is behaving like a "cannibal star" devouring its companion at an unprecedented rate, on its way to an especially violent end - a supernova so bright that, according to calculations, it could even be seen in daylight. Now, a recent analysis of the system, published in the journal Monthly Notices of the Royal Astronomical Society and recently summarized in Live Science, adds a new layer of detail: updated masses of the two stars, precise classification as an "ultra-soft" X-ray source, and a quantitative picture of the giant gas envelope surrounding the system.
The researchers monitored V Sagittae for about 120 days using the X-Shooter spectrograph on the Very Large Telescope in the Atacama Desert in Chile. The spectrograph breaks down the light coming from the system into its colors – a spectrum – and allows us to measure which elements are present there, in what ionization states, and at what speed the gas is moving towards us or away from us. In “normal” binary systems, it is possible to follow the motion of the stars using the Doppler shift of the spectral lines, and from this to deduce their masses. But V Sagittae is far from normal: its light is constantly changing, and the spectral lines are controlled by very fast streams of gas escaping from the disk and not just by the rotation of the stars.
This complexity also explained the long-standing controversy over masses. As early as the 60s, it was suggested that the white dwarf weighed about 0.7 solar masses and the companion about 2.8 solar masses—a highly asymmetric system. The new analysis suggests a more restrained picture: the total mass of the system is probably less than 2.1 solar masses, and each of the two stars weighs about one solar mass. Theoretically, this is still enough to eventually lead to a Type Ia supernova, but the path there may be slower and more gradual than previously thought.
Meanwhile, the high rate of material inflow into the white dwarf is producing a continuous thermonuclear "burn" in its upper layers. This is a well-known mechanism in systems called "supersoft X-ray sources": the white dwarf does not explode yet, but its surface becomes a kind of stable crucible emitting enormous amounts of X-ray radiation at relatively low energies. V Sagittae turns out to be one of the brightest and most extreme sources in this category in the Milky Way galaxy.
But even this "hungry" white dwarf cannot digest everything it steals from its companion. Much of the material is thrown out at high speed, forming a large disk of gas surrounding the two stars – a circumbinary disk. The radius of this disk is estimated to be two to four times greater than the distance between the two stars themselves. One can imagine a small, hot system in the center, surrounded by a wide ring of gas, where some of the material will be drawn back in and some will escape into interstellar space.
All of this is just the middle chapter in the story. At some point, when enough material has accumulated on the surface of the white dwarf, a nova explosion is expected: a sudden ignition of the upper layer of gas, which causes the system to brighten hundreds of thousands of times for a short time. Unlike a supernova, a nova does not destroy the white dwarf; it loses some of its material, balances out – and then can start accreting again. According to the researchers, such a nova in V Sagittae may occur in the coming years, and it will be bright enough to be seen with the naked eye even from Israel, under relatively clear sky conditions.
But the real drama is coming later. Measurements show that the system’s cycle time is gradually getting shorter – a sign that the stars are losing energy and moving closer together. Models published as early as 2020, based on this rate of decline, estimated that the stellar merger and a large supernova would occur around 2083, with an uncertainty of about 16 years in either direction. That means that from the 60s and 70s until the end of the 21st century, there is a reasonable “time window” in which V Sagittae could become one of the brightest events in the night sky – and perhaps even in the daytime sky. Exactly what will happen and when depends on details that have not yet been precisely measured: the masses, the flow rate, the internal structure of the white dwarf.
Despite the drama, there is no reason to panic: the distance of about 10,000 light-years ensures that the explosion will be a spectacular celestial spectacle, but not a threat to life on Earth. For astronomers, V Sagittae is a living laboratory for understanding the evolution of binary systems, the dynamics of soft X-ray sources, and the path that leads from a hungry white dwarf to a supernova. For astronomy enthusiasts, it is an invitation to occasionally raise your eyes towards the Sagittarius constellation and remember that somewhere out there, behind the small dots in the darkness, one of the greatest explosions of the coming generations is already brewing.
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Science has never presented a comprehensive theory about "what's out there"
Ancient man looked up, and immediately the question arose…what is there?
After I discovered the geometry of closed circular lines,
I feel ready to try to answer the question……What's in there?
My attempt to answer the question of what is there?? arises miraculously from me, and must be put to the test of physical reality, by practical experiment – because experiment is the one capable of judging truth or falsehood.
I feel that the answer to the question "What's there?" lies in the exact sciences - geometry and physics, because these sciences deal with continuous quantities, in which it is impossible to identify a beginning or an end.
Geometry deals with continuous quantities of length, area, and volume, and physics deals with continuous quantities of energy, and passive time. The active time that man is accustomed to does not exist in physical reality, and it disappears, the moment you think about it.
Passive time is absolute rest and absolute cold, and it fills the infinite space.
The actual matter that can be touched is created by the combination of massive amounts of time and energy.
Infinite space is full of passive time and energy, and it is the place where stars are created, and it is the place where stars disappear and they give up their energy, and their passive time, to space.
A. Asbar