Betelgeuse is one of the most dramatic stars in our night sky. It's that bright reddish star on the shoulder of Orion, the hunter-shaped constellation, easily visible during the winter in most of the world. But aside from its brightness and its look, Betelgeuse is also a star destined to have a huge and explosive demise. Betelgeuse is a red supergiant, meaning that it's in the final stages of its life. It's about 640 light-years away from the Earth and is amazingly huge—if it were to replace our Sun, its outer edges would extend past Jupiter.

Now, Betelgeuse is consuming the final reserve of nuclear fuel. Having fused millions of years of hydrogen into helium and then helium into heavier elements, it is rapidly nearing the time at which it can no longer hold itself in a stable state. When it does, the star's core will collapse within seconds, and the shockwave caused will rip the outer layers apart and send them flying outward into space. That event is a supernova. Even though we have no idea when Betelgeuse will explode—it might be tomorrow or 100,000 years from tomorrow- we do know that it will. And since Betelgeuse is relatively close to Earth astronomically, its supernova will be a one-time event for those fortunate enough to see it.

What Happens When Betelgeuse Explodes?

When Betelgeuse goes supernova sometime in the future, the explosion will be visible to the naked eye from Earth. It will be so bright that it will even be visible in the daytime for weeks, months. At night, it would outshine all the other stars and even rival the full moon in brightness. To most, seeing something like that in the sky would be unimaginable—something seen in science fiction come to life. The first sign of the explosion will not be a bright one at all. A flash of neutrinos, tiny, nearly massless particles, will race ahead of the light and reach Earth first. The neutrinos will be invisible to us, but very sensitive detectors will pick them up, warning astronomers that something extraordinary has just happened. A few moments later, the light from the explosion will reach us, and the star that had glowed so gently in Orion's shoulder will blaze into a brilliant beacon in the sky.

The real explosion will be intense and brief. The core will collapse inward, then rebound outward and transmit shockwaves outward, shredding the star apart. There will be either a dense neutron star or, if the original star was big enough, a black hole. For Betelgeuse, a neutron star is likely what remains behind—a small, incredibly dense object about the size of a city but more massive than our Sun.

Fortunately for us, Betelgeuse is far enough away that this explosion will never be a threat to life here on Earth. Supernovae do release hazardous radiation, but that type of effect only becomes deadly if the explosion is within about 50 light-years. Since Betelgeuse is more than ten times farther away than that, we have the fireworks without the nuclear waste.

How Orion Will Be Affected?

Orion is perhaps the most identifiable and most familiar constellation of the evening sky. If you're a professional astronomer or simply an individual who likes to gaze out into the evening sky on a clear night, you've most likely spotted Orion's unmistakable outline. Perhaps the most identifiable stars are those that form Orion's Belt, but Betelgeuse has a large role to play, too. It's the star that marks Orion's left shoulder and forms part of the constellation's recognizable, warrior-like shape.

When Betelgeuse finally explodes and eventually vanishes, Orion will lose one of its brightest and most important stars. Briefly, at the supernova phase, Orion's shoulder will be shining all the more brightly—so brightly, indeed, as to dominate the rest of the constellation. But when the light fades, Betelgeuse will be gone from the sky forevermore. This will render Orion with a "missing" shoulder, changing the face of the constellation to the eye.

It's strange to think that a constellation we've always known can just suddenly look different from what it once did. Orion has been a figure in many myths and tales throughout cultures and centuries, believed to be some kind of powerful hunter or warrior. To lose Betelgeuse would be like changing a familiar painting that's hung on the wall for decades. While the other stars in Orion will still be there, the constellation itself will never look the same again. Nevertheless, constellations are merely shapes we have made out of what we observe. The stars of Orion are not actually near each other—they just seem that way from our planet. Therefore, although Betelgeuse's vanishing will alter the image, it's part of the normal cycle of stars, and it puts us in our front-row seats in front of the cosmos in action.

Why This Supernova Will Mean Something to Science?

For scientists and astronomers, an explosion of Betelgeuse would be a treasure trove of data and discovery. Supernovae are essential to learning about the universe. Supernovae scatter elements such as carbon, oxygen, and iron—building blocks of planets and life itself—across the universe. From the calcium in our bodies to gold jewelry, it was all produced in supernovae from long ago. The explosion of Betelgeuse will propel all manner of heavy elements into the local part of space and into the process of cosmic recycling that creates new stars, planets, and potentially even life. What makes Betelgeuse so especially interesting to study is how well we've already investigated it. It's one of the most well-explored stars in the night sky, so when it goes supernova, we'll have "before" and "after" data to tell us what exactly happens to large stars when they die. Ground-based and space-based telescopes will work together to monitor all the details we can, from X-rays to infrared radiation to gravitational waves. This will allow scientists to test hypotheses, refine models of star behavior, and perhaps even resolve long-standing debates about how black holes and neutron stars form.

In addition, Betelgeuse's supernova would create public interest in space like we have never seen since something as monumental as the moon landing or the discovery of exoplanets. It would be visible to everybody, not just astronomers who have very powerful telescopes. People across the globe could look up and see something beautiful, something that reminds us that we are small but part of the universe.

A Brilliant Finish, A New Start 

The last supernova of Betelgeuse will be one of the most striking and scientifically significant events in astronomy today. It will illuminate the sky in a manner that fewer individuals have experienced, leave a lasting imprint upon the familiar profile of Orion, and provide a new avenue for scientific investigation and discovery. Regardless of when that is, however, we also know that it will. No matter if that is tomorrow or many decades after we are dead and gone, Betelgeuse's demise will remind us anew of how vibrantly alive the universe is. And when it does happen, we will not only be losing a star. We will be witnessing the end of one chapter in the universe and the beginning of another.

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