There are spectacular astronomical events that we may be lucky enough to see more than once in our lives, such as a total solar eclipse, the luminous trail of a superbolide in the night sky, or majestic comets. But one A much more exceptional event is about to occur in the sky, which could begin as early as tonight. It is a stellar explosion known as “nova”.
A NASA recently announced that an astronomical phenomenon of this type will soon be visible to the naked eye for several days.
A new (and ephemeral) point of light in the sky
This rare but spectacular event consists of a sudden increase in brightness in a certain region of space. From Earth, it will appear as if a star has suddenly appeared. It will appear in the small constellation Corona Borealis, in a location about 3,000 light years from Earth.
Several of the brightest stars in this constellation are home to planetary systems, including Negolu, a Jupiter-like planet whose atmosphere contains water vapor. It is in this section of the sky that a new point of light will appear, the result of a stellar explosion in a binary system composed of a white dwarf star and a red giant.
How and when do these nova-like explosions originate, and what will this new object look like in the sky?
A thermonuclear explosion
A new star is not forming, nor is it a “star death” (as is the case in events such as a supernova). The observed glow is the result of thermonuclear reactions in a binary system of two stars orbiting each other: the T Coronae Borealis (T Cr) system.
One of the stars is a white dwarf (called T CrB) with a mass similar to that of the Sun and a diameter about 100 times smaller, a circumstance that gives rise to an intense gravitational field. Its companion star, the red giant called T CrA, is losing matter (mainly hydrogen) due to the strong gravitational pull of T CrB. And this hydrogen is gradually being deposited on the surface of the white dwarf.
As a result, the hydrogen concentration in the white dwarf constantly increases and there is an increase in pressure and heat until it reaches a limit. The star then erupts in a colossal thermonuclear explosion, similar to the detonations of atomic fusion bombs here on Earth.
After this violent episode, the dwarf star will return to its original state, once again capturing hydrogen from its companion until the nova explosion repeats itself in about 80 years. This is why it is so difficult to witness this event twice in one lifetime.
New recurring or periodic
Normally, we cannot predict with certainty when such a stellar explosion will occur. However, there is a small group of white dwarf binary systems that generate novae periodically, that is, they repeat themselves in cycles of a few decades. We are talking about new recurring or periodic ones and, fortunately, the T CrB system belongs to this select club.
In addition to knowing the periodicity in which the white dwarf captures hydrogen to the limit, researchers have other clues about the imminence of this nova event. Thus, according to NASA scientist William J Cooke, the dimming of a white dwarf during a previous period of one year is a clear sign of an approaching stellar explosion. And T CrB started to darken in March 2023.
So what exactly will we see in the night sky, likely on a night this summer in the Northern Hemisphere?
Bright like the polar star
When cataloging bright objects in the sky, such as planets or stars, astronomers use a well-known parameter called apparent magnitude.
Basically, it is related to the brightness of a star as it appears in the night sky, and depends on the star’s intrinsic brightness and its distance from us. The lower the apparent magnitude value, the brighter the object in the sky.
Thus, for example, the apparent magnitude of the full Moon is -12.6, that of the star Sirius (the brightest star in the night sky) is -1.46, while the polar star (Polaris) has a value of +2.
The T Cr star system has an apparent magnitude of +10, but when the next nova explosion occurs, its visibility will increase significantly to +2, comparable to the brightness of the polar star.
It will be at this exact moment that we will be able to see this new “star” with the naked eye for several days, without the aid of any optical device, before it dims and disappears again, possibly for another 80 years.
We will witness a unique astronomical event: the thermonuclear explosion of a white dwarf. For those who don’t know what’s going on up there, it will look like the birth of a short-lived star.
This article is republished from The Conversation; Read the original article
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