Betelgeuse, the bright, reddish star marking the shoulder of the Orion constellation, is nearing the end of its stellar life cycle. This massive star has exhausted the majority of its nuclear fuel and is destined to explode in a spectacular core-collapse supernova. The question of when this cosmic explosion will happen drives astronomers to study its erratic behavior.
Betelgeuse’s Status as a Red Supergiant
Betelgeuse is categorized as a red supergiant, possessing enormous mass and having swelled to an immense size. Its diameter is large enough to engulf the orbits of the inner planets if it were placed at the center of our solar system. With a mass 10 to 20 times that of the Sun, the star burned through its fuel supply rapidly over its short lifespan of less than 10 million years.
For millions of years, Betelgeuse fused hydrogen into helium in its core, maintaining stability against gravity. Once the hydrogen ran out, the core contracted and heated up, initiating the fusion of helium into carbon and oxygen. This process forced the star’s outer layers to expand and cool, giving Betelgeuse its characteristic enormous size and reddish color.
The star is now progressing through subsequent, shorter-lived burning phases involving heavier elements. Each new fusion stage lasts for a shorter period than the last. Once the star begins fusing carbon, the remaining time is drastically reduced, signaling the consumption of its final substantial fuel sources.
Understanding the Supernova Timeline
Predicting the exact moment Betelgeuse will explode is impossible due to the complex internal physics of an aging star that cannot be directly observed. Based on current models of stellar evolution, astronomers estimate the supernova explosion will occur sometime within the next 100,000 years. Betelgeuse is widely considered the next major supernova candidate in our corner of the galaxy.
The final trigger occurs when the star’s core begins creating iron, the last element in the fusion chain that does not release energy when fused. Once the core is primarily iron, fusion stops completely, and the core instantly collapses under its immense weight. This catastrophic collapse initiates a shock wave that tears through the star’s outer layers, resulting in a Type II core-collapse supernova.
The stages leading up to the iron core formation, such as carbon burning, can last for hundreds or thousands of years, but the final collapse takes only seconds. The most precise warning scientists would receive is a burst of neutrinos, nearly massless particles released in the final moments of the core collapse. These neutrinos would reach Earth hours before the light from the actual explosion, providing the only scientific heads-up.
Some recent studies analyzing the star’s pulsation cycles suggest Betelgeuse might be further along in its carbon-burning phase than previously thought. This has led to speculation that the remaining time could be as short as a few hundred years. However, these shorter estimates remain highly uncertain and are subjects of ongoing debate.
The Great Dimming Event of 2019-2020
Betelgeuse captured public attention in late 2019 when it began an unprecedented drop in brightness, dubbed the “Great Dimming.” The star’s luminosity fell by nearly two-thirds, leading to speculation that the dimming signaled an imminent supernova explosion.
Scientific analysis determined the cause was not related to the core running out of fuel, but rather a massive eruption on the star’s surface. Observations confirmed Betelgeuse ejected an immense amount of superhot material, similar to a stellar coronal mass ejection.
This material traveled away from the star, cooled down, and condensed into a massive cloud of starlight-obscuring dust. This dust cloud temporarily blocked the light from a quarter of Betelgeuse’s visible surface from our perspective on Earth. Betelgeuse returned to its typical brightness range by April 2020, confirming the temporary nature of the dust veil.
What the Supernova Will Look Like From Earth
When Betelgeuse finally explodes, the Type II supernova will be the most spectacular celestial event witnessed by humanity in centuries. The star is located approximately 400 to 600 light-years from Earth, a distance far enough away to pose absolutely no danger to our planet. Studies indicate a supernova must occur within about 160 light-years to cause any harm from radiation.
The explosion will cause Betelgeuse’s brightness to surge dramatically, instantly outshining every other star in the night sky. At its peak, the supernova is expected to rival the brightness of the half-Moon. This concentrated point of light will be so intense that it will be easily visible during the day for many weeks.
The sudden appearance of this brilliant new point of light will fundamentally alter the familiar shape of the Orion constellation. The supernova will remain at its peak brightness for several weeks before slowly beginning to fade over several months. It is expected to be visible to the naked eye for more than a year before becoming too faint to see.