What truly occurs when a star meets its end? The question became especially intriguing in 2019 when Betelgeuse, the famous red supergiant star located in the constellation Orion, experienced a notable dimming. This event led to widespread speculation that it might soon detonate as a supernova. However, it seems that an explosion isn't imminent just yet. To grasp what awaits Betelgeuse, we can take a closer look at the nearby Crab Nebula.
Betelgeuse is easily identified as the reddish shoulder star of Orion and is classified as a variable star. This means its brightness fluctuates over time, and it often competes with Rigel, a striking blue-white star, for the title of the brightest star in this constellation. Although Betelgeuse is relatively young in cosmic terms—only a few million years old—it lives life in the fast lane due to its enormous size. As a supergiant, it has already burned through the hydrogen fuel in its core and has shifted to fusing helium. This transition has caused its outer layers to cool and expand significantly, resulting in its massive size, which is comparable to the distance between Mars and Jupiter.
One fascinating aspect of Betelgeuse is that it's one of the few stars for which astronomers have gathered detailed observations of its surface, thanks to its proximity of about 642 light-years from Earth. Moreover, Betelgeuse is classified as a 'runaway star,' suggesting that it may have been propelled to its current speed after merging with a smaller companion star. If this hypothesis holds true, Betelgeuse could potentially have millions of years left before it finally goes supernova! So, while we may wonder about its potential for imminent explosion, the truth remains that we still have much to discover about this captivating celestial body.
In contrast, the Crab Nebula (M1), located in the neighboring constellation Taurus, serves as a dramatic reminder of what happens during a star's cataclysmic end. This stunning nebula is the remnant of a supernova that was witnessed by astronomers in the year 1054. Through a backyard telescope, you can observe some aspects of its eerie, spiderweb-like gas clouds. However, only advanced telescopes can unveil the swiftly spinning neutron star at its center—this is the last remnant of the stellar explosion that created the nebula. The gas clouds that constitute the Crab Nebula were ejected during the violent death of the massive star and continue to expand outward, enriching the cosmos with heavy elements such as silicon, iron, and nickel. These element-laden clouds act like cosmic fertilizer, playing a crucial role in forming rocky planets, including our own Earth. Additionally, supernovae generate powerful shock waves that can trigger new star formation. Remarkably, if it hadn't been for a supernova occurring long ago, neither our solar system nor we would exist today! For those eager to delve deeper into the Crab Nebula, NASA’s James Webb Space Telescope offers a comprehensive video that can be found at bit.ly/CrabNebulaVisual.
Are you curious about the life cycle of stars and how they evolve over time? Check out "The Lives of Stars" activity and accompanying handout available at bit.ly/starlifeanddeath, part of our SUPERNOVA! toolkit at nightsky.jpl.nasa.gov.
This content originally appeared in February 2020, crafted by Dave Prosper, and has been updated by Kat Troche in December 2025.
