Betelgeuse, one of the most recognizable stars in the night sky, marks the shoulder of the Orion constellation. Its distinct reddish-orange glow has captivated observers for millennia, but modern attention focuses on its current state. Scientists have determined this star is nearing the end of its life, destined for one of the universe’s most violent events: a supernova. Predicting when this will happen is a compelling mystery in astrophysics today.
Betelgeuse: A Nearby Red Supergiant
Betelgeuse is classified as a red supergiant, representing a late and expansive stage in the life of a massive star. The star has swelled to an immense size; if placed at the center of our solar system, its outer layers would extend past the orbits of Mars, possibly reaching nearly to Jupiter.
Its size is variable, fluctuating between approximately 640 and 764 times the radius of our Sun, which causes its brightness to change over time. The star is located approximately 500 to 700 light-years away from Earth, a relatively short distance in galactic terms. This proximity and its intrinsic brightness make Betelgeuse typically one of the ten brightest stars visible in the night sky.
The Mechanics of Stellar Death
The eventual explosion of Betelgeuse will be a Type II core-collapse supernova, the fate of all stars that begin with a mass roughly eight times greater than the Sun. For much of its life, Betelgeuse sustained itself by fusing hydrogen into helium in its core, generating outward pressure to counteract the star’s immense gravity. Having exhausted its central hydrogen, the star is now fusing heavier elements in a series of concentric shells.
The star is currently fusing helium into carbon and oxygen in its core, while hydrogen fusion continues in a shell outside the core. This process is temporary, and the star will continue to fuse progressively heavier elements, such as neon, oxygen, and silicon, until it creates iron. Iron fusion does not release energy; instead, it consumes it, meaning the star can no longer generate the outward pressure needed to support its own weight.
Once the iron core reaches a certain mass, known as the Chandrasekhar limit, the core begins a catastrophic gravitational collapse. This collapse happens incredibly fast, in a fraction of a second, compressing the core material to nuclear densities. The core rebounds violently, sending a powerful shockwave outward through the star’s outer layers, resulting in the supernova explosion.
Why Timing the Supernova is Impossible
Predicting when Betelgeuse will explode remains highly uncertain. The current scientific consensus places the star’s remaining lifespan somewhere within the next 100,000 years, an instant on a cosmic timescale. However, some recent models based on the star’s pulsation periods suggest a much shorter timeframe, possibly within the next few hundred years or even decades.
The difficulty in making a precise prediction stems from the fact that the final, most rapid stage of stellar evolution occurs deep within the star’s interior, hidden from direct observation. Astronomers cannot directly measure the current composition or density of the star’s core to determine how much fuel remains until the iron core forms. The star’s external activity, such as the dimming event observed in 2019-2020, does not reliably indicate an imminent core collapse.
That dimming was caused by the star ejecting a large cloud of superhot material that cooled to form a dust cloud, temporarily blocking light from a portion of the star’s surface. While this mass loss shows Betelgeuse is volatile and late in its life, it is an external phenomenon that does not signal the internal core dynamics are at the point of collapse. The internal changes leading to the final explosion happen on timescales too fast to observe in advance with current methods.
Observable Effects and Earth Safety
When Betelgeuse explodes, the light from the supernova will take approximately 500 to 700 years to reach Earth, meaning the event we observe will have already happened centuries ago. The resulting supernova will briefly become one of the brightest objects in the night sky. Estimates suggest it could shine as brightly as the half-Moon and be visible during the daytime for several weeks or months.
For astronomers, the sudden appearance of this new, extremely bright object will temporarily overwhelm most telescopes, making observations difficult. For the general public, it will be a celestial event that alters the familiar shape of the Orion constellation. The star will slowly fade over the course of a year or two, eventually leaving behind a nebula and a small, dense remnant like a neutron star.
The explosion poses no threat to life on Earth due to the star’s distance. A supernova would need to occur within about 50 light-years of our solar system to cause significant damage from harmful radiation, such as gamma-rays, to Earth’s ozone layer. At a distance of 500 to 700 light-years, Betelgeuse is well outside this danger zone.