What Is a Supernova? The Fate of Huge Stars

A clear starry sky is a cosy thing. The stars are not a part of it and are not affected by anything that is going on here. Yet that quiet is only apparent. All of the stars up there are on their own timetable — formed from clouds of gas, and living for millions or billions of years, and then, in some way or other, dying.

Not for the biggest stars in the universe, anyway, death is not a slow fade. It’s an explosion so strong that it can outshine an entire galaxy for a brief time. That explosion is known as a supernova, and there is no need for a telescope, a physics degree or special equipment to understand it — just some curiosity of what is going on in the sky above our heads each night.

At the conclusion of this post, you will know what a supernova is, why big stars do not just die and go away, and how oddly enough, the universe’s most violent events are the source of our existence.

What Is a Supernova?

In essence, a supernova is the death of a star in an explosive manner. A single star can be as bright as billions of stars for a few days to a few weeks. For perspective, in that single flash of light, a supernova will emit more energy than our Sun will in the course of its entire 10 billion-year life.

A supernova may seem like simply a light show, but it’s so much more. These explosions are one of the principal recycling processes of the universe. This releases heavy metals — iron, calcium, gold, and heavy metals beyond — into the space, and the material so released becomes incorporated into the matter of new stars, new planets, and yes, even new living things. The definition of a supernova is not just an astronomy trivia question. A strand of awareness and noticing that we all share.

Why Do Stars Explode? The Gravity vs. Fusion Battle

In order to understand the process of the explosion of a star, it is important to understand how the star lives. All stars are engaged in a continual tug of war between two forces.

There is a force on one side — gravity, which is always trying to pull the mass of the star toward itself and bring it together. At the other extreme, however, is the outward pressure generated by nuclear fusion taking place at the very center of the star: hydrogen is being fused into helium, and, in bigger stars, helium is being fused into elements even heavier. For so long as the star has fuel to fuse, the balance remains and the star is stable.

The trouble begins when the fuel is depleted.

For massive stars (usually about 8 times the mass of the Sun or more), fusion does not stop at helium. As the star progresses through its life it continues to ascend the periodic table: helium turns to carbon, carbon turns to oxygen, neon turns to silicon, silicon to iron, and so on until iron is formed in the core.

The twist is that fusion of iron doesn’t release energy as the earlier fusion reactions did. It actually absorbs energy. After all, when a large star’s core becomes iron, the fusion process cannot overcome the force of gravity. The core starts to collapse in a matter of seconds, and the star’s outer layers fall onto the core. The star explodes with a huge rebound explosion, the supernova, throwing out the star’s outer layers at tremendous speed.

The Two Types of Supernovae

Not all supernovae are created equally. In general, astronomers divide them into two categories.

Massive Star Core Collapse

The first is a huge star collapse due to the fuel running out, iron core collapsing, and the explosion. This is the most common form that people visualize when they consider a star going “supernova.”

White Dwarf Explosions

The second type is a bit different and does not involve any single large star. It occurs in binary star systems — two stars that orbit around one another closely. One of these is a white dwarf, a tiny dense remnant of a dead star. The white dwarf, over time, gradually sucks in material from its companion, increasing its mass. It eventually passes a tipping point and becomes unstable, and then undergoes an unstable nuclear explosion which completely destroys it.

Supernovae are both processes, but they differ greatly in the type of star, the arrangement of the star, and the mechanism that causes each of them.

Neutron Stars, Black Holes, and Remnants

With the fading of the light, a supernova doesn’t end. It leaves a remnant after it dies — and what that remnant is depends on how massive the original star is.

If the star is relatively small, a remnant of the star’s core is left behind, and it is a neutron star, an object so dense that a teaspoonful of its matter would weigh billions of tons on Earth. The most massive of the stars collapse even more, crushing the core down into a black hole — a place where gravity is so strong that even light cannot escape.

But the outer material that is blasted away in the explosion doesn’t simply disappear either. It creates what is known as a “supernova remnant,” a cloud of gas and dust that may continue to shine for thousands of years. One of the best known is the Crab Nebula, the glowing remnants of a supernova witnessed by ancient astronomers in the year 1054.

Many Famous Supernovae Have Been Seen Throughout History

Supernovae are not only recent astronomical phenomena; they have been observed exploding in the sky for a very long time.

The above-mentioned supernova, which gave rise to the Crab Nebula, has been recorded by astronomers in China and elsewhere almost 1000 years ago as a new and temporary star appearing in the daylight sky. Centuries later, astronomers Tycho Brahe and Johannes Kepler both observed their own supernovae in 1572 and 1604, respectively, which helped to discredit the ancient theory that the heavens were fixed and immutable.

In 1987, astronomers detected a supernova, or explosion, in the nearby galaxy of the Magellanic Cloud, called SN 1987A, providing today’s astronomers equipped with more sophisticated instruments a first-hand chance to study the process as it happened. Each of these events, centuries removed, has a similar story — even stars have finite lives.

What Role Do Supernovae Play in Our Lives?

What could be more distant than thousands or millions of light-years? Supernovae directly produce almost all of the heavy elements you could imagine — the iron in your blood, the calcium in your bones, the oxygen in the air you breathe.

All of these could not have been created within a regular, normal star. They need the high temperatures and high pressures of a supernova explosion. “Star stuff” is not just a poetic phrase coined by Carl Sagan; it’s a pretty literal description of the origin of your atoms. At some point, at some place, a star exploded, and some of the debris became you.

Explaining the Confusion: Nova vs. Supernova vs. Hypernova

These three words are similar in sound and can be confused, but they refer to very different events.

A non-destructive explosion on the surface of a white dwarf is a much smaller nova. The white dwarf will survive, and the same star can have several novae in its lifetime. A supernova, on the other hand, is a complete and massive star explosion — the sort of explosion we’ve talked about throughout this post. On the extreme end is a hypernova, which is an extremely powerful supernova that can cause intense gamma radiation, usually from an extremely massive, rapidly rotating star.

In brief, novae are modest, predictable, and recurring stellar explosions, while supernovae are catastrophic and terminal, and hypernovae are the extreme, rare form of the same catastrophic event.

Stargazing on a Budget

To feel like you’re really very involved in all of the above, you do not have to go to a research observatory or own costly equipment. The best stargazing experiences can begin with just a clear night, a bit of patience, and your own eyes.

If you want to get more involved in exploring the night sky yourself, the following tips can help. Constellations, planets — even satellites overhead — can be identified in real time without the help of any equipment with the aid of free stargazing and astronomy apps. The conditions available to the observer can make a huge difference — if there is no light pollution, even a nearby park or open field away from the street lights can make a huge difference. If you do decide at some time to purchase binoculars or a new telescope, don’t break the bank to start; it’s a good idea to shop around and look for sales or coupons on entry-level equipment — quality can be similar, but prices can be quite different.

Stargazing is a hobby that requires no expense and can be pursued gradually over a lifespan, at your own pace and own budget.

Conclusion

A supernova doesn’t just fade into the night sky; it is one of the great processes of the cosmos and a part of our own story, wrought in a quiet manner. When a huge star collapses, it disperses the very same elements on which new stars, new planets, and eventually, life, is built.

Praise doesn’t have to cost a lot of money. The curiosity about the night sky is free, and the next clear evening that you look up outside, you’re gazing at a history that is older and larger than anything down here. It’s a sobering reminder that some of the stuff we are is actually from a star that exploded long before Earth existed — a reminder that we are all a part of something so much bigger than ourselves.

Frequently Asked Questions

In simplest terms, what is a supernova?

It’s a huge star that dies in a flash, sending out a tremendous amount of energy and light.

Why does a star become a supernova?

Typically either a large star that has run out of nuclear fuel and collapses, or a white dwarf star in a binary system that becomes too massive and explodes.

What is the lifetime of a supernova?

The initial explosion is very rapid, but the bright light can be seen in the sky for weeks or even months before it fades.

Is there a possibility that a supernova will impact us in the near future?

There are no worries in the near future, as the nearest known supernovae have been found at safe distances, and astronomers keep a close eye on potential candidates.

What’s the difference between a supernova and a black hole?

The massive exploding star is the supernova, and the supernova remnant may become a black hole, depending on the mass of the original star.