Betelgeuse, a star in the Orion constellation, has captured human attention for centuries due to its prominent reddish hue. This star marks the hunter’s shoulder and is nearing the end of its life cycle. Its impending explosion as a supernova represents a major astronomical event.
The Red Giant: Profiling Betelgeuse
Betelgeuse is classified as a Red Supergiant, a late and expanded phase in the evolution of a massive star. With a mass estimated between 10 and 20 times that of our Sun, Betelgeuse has rapidly burned through its nuclear fuel. It has swelled to a diameter 700 to 1,000 times larger than the Sun. If Betelgeuse were placed at the center of our solar system, its outer edge would extend past the orbit of Jupiter, engulfing the inner rocky planets.
The star is located about 700 light-years away, meaning the light we observe today left the star 700 years ago. Its powerful fusion rate caused it to reach the end of its life much faster than smaller stars like our Sun. Stars with at least eight solar masses do not form a stable white dwarf; instead, their high mass dictates they will undergo a core-collapse supernova.
The Mechanics of a Core-Collapse Supernova
Nuclear fusion in the core dictates the fate of a star like Betelgeuse. Massive stars fuse lighter elements into heavier ones, creating an internal structure with different elemental shells. This process provides the outward thermal pressure that counteracts the star’s inward gravitational force.
Fusion eventually reaches silicon, which burns quickly to produce a dense core of iron and nickel. Iron is a nuclear dead end because its fusion consumes energy rather than releasing it, causing the core to lose its outward pressure source. When the iron core’s mass exceeds the Chandrasekhar limit (about 1.4 times the mass of the Sun), it can no longer be supported by electron degeneracy pressure and begins to collapse rapidly under its own gravity.
This core implosion occurs within seconds, with material accelerating up to 30,000 kilometers per second. The collapse is halted when the core reaches nuclear density, causing an energetic rebound that generates a powerful shock wave. Nearly all of the gravitational binding energy is released in a burst of neutrinos. These neutrinos help energize the shock wave and propel the star’s outer layers outward in a Type II supernova explosion.
Predicting the Event: The Timeline Dilemma
When Betelgeuse will explode is difficult to determine, as “imminent” in astronomical terms spans a vast timeframe. Estimates suggest the star will explode within the next 100,000 years.
Scientists estimate the remaining lifespan by studying the star’s internal state, including its core density and fusion rates. Recent research based on the star’s pulsation periods has suggested a shorter timescale, perhaps “tens of years,” but this remains an active area of study. The first warning sign of core collapse would be a surge of neutrinos that would reach Earth several hours before the visible light from the explosion.
The dimming event Betelgeuse experienced between late 2019 and early 2020 sparked widespread speculation about an imminent supernova. During this “Great Dimming,” the star lost nearly two-thirds of its brightness, dropping significantly in rank. Scientific consensus indicates this was not a pre-supernova event. Observations suggest the dimming was caused by the star ejecting hot plasma from its surface. This material cooled into a cloud of dust, temporarily blocking light from about a quarter of the star’s surface.
The Celestial Spectacle: What Earth Will Witness
When Betelgeuse finally explodes, the supernova will shine with an apparent magnitude that could rival the brightness of the Full Moon, concentrated into a single point of light. This extreme brightness will make it easily visible in the daytime sky for several months.
The peak brightness will persist for weeks to months, driven by the radioactive decay of elements, such as Cobalt, created during the explosion. Over the course of a year or two, the light will gradually fade until the remnant is no longer visible to the naked eye. Due to the star’s distance, the explosion poses no physical threat to life on Earth.
The aftermath will leave a lasting legacy. The star’s outer layers will expand outward as a colorful, gaseous cloud known as a supernova remnant or nebula. The star will be replaced by a dense, compact object at the core, likely a neutron star or, depending on the final core mass, a black hole. Once the remnant fades, the constellation Orion will appear noticeably different, missing the star that once marked its left shoulder.