Sometime between now and the end of the year, a big star explosion is likely going to glow in the night sky. This outburst, dubbed a nova, is projected to be so dazzling that it will be seen even from large cities. The explosion won’t pose any risk to Earth — it’s too far away — but over a duration of few days, the nova will release tens of thousands of times more energy than the Sun puts out over an entire year.
The outburst will come from the star system T Corona Borealis, which puts on a comparable spectacle every 80 years or so. Astronomers presently expect approximately a 70% likelihood that T Corona Borealis will go nova by September, and a 95% chance that it’ll go off before the end of the year. The nova will likely be the brightest one observed on Earth since 1975.
What Creates A Nova?
A nova is a runaway thermonuclear explosion that is, in essence, not too dissimilar from a massive hydrogen bomb. But instead of exploding out of a metal casing, a nova’s explosion occurs on the surface of a white dwarf star.
White dwarfs are the smoking ashes of stars like the Sun. Right now, the nuclear fusion of hydrogen in the Sun’s core creates energy that pushes back against gravity and saves the Sun from collapsing in on itself. Eventually, however, the Sun will run out of fuel for fusion and collapse until it’s roughly the size of Earth. At that point, the Sun won’t be able to become much denser without shoving its electrons over a limit defined by quantum physics. When a star reaches this stable, ultra-dense phase, it becomes a white dwarf.
On its alone, a white dwarf won’t generate a nova. It needs to be in a binary system, meaning it and another star circle one another. If the other star still has enough of hydrogen, and if it is not too distant from the white dwarf, then the white dwarf’s gravity will skim off part of the other star’s outer layers. Over time, this fuel might collect on the surface of the white dwarf and heat up. When the fuel becomes hot enough, it will ignite in a quick chain reaction, generating a tremendous blast of radiation and hurling forth ejecta at thousands of kilometers per hour.
Though this explosion is highly intense, it doesn’t kill either star. The identical sequence of build-up and explosion might recur again and again. T Corona Borealis, in instance, repeats its nova cycle around every 80 years. The system consists of a white dwarf and a red giant star situated around 800 light-years from Earth.
What’s The Difference Between A Supernova And A Nova?
A supernova is a significantly greater stellar explosion that does not happen more than once to the same star. Some supernovae are generated when a star runs out of fuel for nuclear fusion and collapses, while others are created by white dwarfs that collect enough mass. Regardless of the precise route, the cause of a supernova must to be sufficiently big that its gravity exceeds the quantum mechanical pressure that would keep a white dwarf stable. And whereas a nova leaves its star system intact, a supernova results in a neutron star or black hole, or entirely destroys whatever object initiated it.
Supernovae are also rarer than novae. The last supernova to happen in the Milky Way was in 1604, and the last nova was in 2022, however it was too faint to observe with the human eye.
How Do We Know A Nova Is Going To Happen?
Some novae reoccur rather regularly, once per hundred years or more. If anyone spotted these “recurrent novae” when they erupted in the past, scientists may study how light from the system altered in the lead-up to each outburst and seek for comparable behavior today.
People have recorded novae from T Corona Borealis four times in the past. In 1217, an abbot in Germany wrote about it as a “wonderful sign.” In 1787, the nova was detected again by an English astronomer. And in 1866 and 1946, scientists throughout the globe obtained precise measurements of how the system’s brightness altered over time.
In 2015, scientists found that T Corona Borealis was approaching the same kind of phase that preceded its 1946 outburst by eight years. They originally projected the system would explode in the mid-2020s. Over time, experts have reduced the timetable down to around a 70% risk of an outburst by September 2024 and a 95% chance of it by the end of the year.
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How To Observe The T Corona Borealis Nova
When it becomes nova, T Corona Borealis should be visible to the naked eye at night from even reasonably light sky, including those in the heart of metropolitan areas. It will decrease dramatically within days, however, so the best time to attempt to notice it will be as soon as the news breaks.
At that moment, the nova will be roughly as brilliant as Polaris, the north star, which is among the top 50 brightest stars in the whole night sky. As the nova dims to the point where it’s no longer feasible to see with the unassisted eye, it may still be possible to watch with binoculars or other special equipment.
The nova will emerge in the constellation Corona Borealis, or “northern crown,” which is positioned between the Hercules and Boötes constellations. This area of the sky should be visible from most locations on Earth except for the deep south, near to Antarctica. The nova won’t seem like an explosion, but like a new star that wasn’t there before. So, to really appreciate this celestial event, it’s worth gazing up and observing that you can’t see the system before it turns nova.
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