Our universe contains an astonishing variety of stars, ranging from the smallest dwarfs to the most expansive supergiants. Our Sun, a familiar presence in our sky, serves as the central star of our solar system, providing the energy that sustains life on Earth. Far beyond our solar system, nestled within the constellation Orion, shines Betelgeuse, a star whose sheer scale dwarfs our Sun. Comparing these two celestial bodies reveals a profound difference in size, offering a glimpse into the diverse lives and ultimate fates of stars.
Our Sun: A Stellar Baseline
Our Sun is a yellow dwarf star, a common type of star in the Milky Way galaxy, though it appears exceptionally large and bright to us due to its proximity. It has an average diameter of approximately 1.39 million kilometers (864,000 miles). This immense size makes it the dominant gravitational force in our solar system, holding all the planets, asteroids, and comets in orbit around it. The Sun’s stable energy output has allowed life to thrive on Earth for billions of years, making it our primary stellar reference point.
Betelgeuse: A Colossal Red Supergiant
Betelgeuse is classified as a red supergiant, a type of star representing a late stage in the evolution of very massive stars. It is easily recognizable by its distinct reddish hue and is located in the shoulder of the constellation Orion. This star is one of the brightest and largest stars visible to the naked eye. Its enormous size is a characteristic feature of red supergiants, which have expanded dramatically after exhausting the hydrogen fuel in their cores.
The Immense Scale of Difference
The size difference between Betelgeuse and our Sun is significant. While the Sun’s diameter is about 1.39 million kilometers, Betelgeuse’s diameter is estimated to be around 764 times that of the Sun. If Betelgeuse were placed at the center of our solar system, its outer layers would extend well beyond the orbit of Mars, potentially engulfing Jupiter.
Millions of Suns could fit inside Betelgeuse. This illustrates the incredible range of sizes stars can achieve and highlights how tiny our Sun is when compared to such a stellar behemoth.
Stellar Evolution and Betelgeuse’s Size
Betelgeuse’s immense size is a direct consequence of its evolutionary stage and initial mass. Stars like our Sun spend billions of years fusing hydrogen into helium in their cores, maintaining a stable size. When they exhaust their core hydrogen, they expand into red giant stars, but not to Betelgeuse’s extreme scale.
Massive stars, which are born with many times the mass of our Sun, follow a different and much faster evolutionary path. After their main sequence phase, they exhaust their core hydrogen and begin fusing heavier elements. This process causes their outer layers to cool and expand dramatically, transforming them into red supergiants like Betelgeuse. Its current size is a temporary phase, indicating it is nearing the end of its life cycle.
Betelgeuse’s Eventual Fate
As a red supergiant, Betelgeuse is destined for a supernova explosion. Unlike Sun-like stars that eventually shed their outer layers to form planetary nebulae and cool into white dwarfs, massive stars like Betelgeuse conclude their lives this way. This occurs when the star’s core runs out of nuclear fuel and collapses under its own immense gravity.
The core collapse triggers a violent rebound, expelling the star’s outer layers into space at tremendous speeds, creating an incredibly bright, temporary celestial event. A supernova can outshine an entire galaxy for a brief period. Following the supernova, the remnant core of Betelgeuse will likely become a neutron star or, if it is massive enough, collapse further into a black hole.