Podcaster: Avivah Yamani
Title: Space Stories: When Stars Explode: From Nova to Kilonova
Organization: Planetary Science Institute; langitselatan
Link : http://langitselatan.com
Description: The night sky isn’t still. It’s full of brief, brilliant flashes called transient objects. In this episode we explain what they are, why they matter, and how you can help chase them!
Bio: Avivah Yamani is a an astronomy communicator from Indonesia and Project Manager of 365 Days of Astronomy.
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Transcript:
Hello everyone, I’m Avivah Yamani, your host today. And you’re listening to 365 Days of Astronomy.
Welcome to the 365 Days of Astronomy, where every day brings you closer to the stars. I’m [Name], and today we’re diving into the explosive lives of stars. Literally.
Can stars explode? Oh yes, they can. Not all of them, and not all at once—but when they do, the Universe takes notice. In fact, some of the most powerful explosions in the universe come from stars at the end of their lives. These celestial fireballs don’t just quietly fade away—they go out with a bang. Or… a nova, a supernova, a kilonova, and even a hypernova!
Some eruptions brighten an otherwise faint star for a few weeks. Others outshine entire galaxies and forge the elements that make planets—and people—possible.
Sounds dramatic? Let’s rewind a bit.
Let’s start in 1572. Danish astronomer Tycho Brahe saw something strange in the night sky—an incredibly bright new star in the constellation Cassiopeia. It wasn’t on any star map. Brahe called it Stella Nova—Latin for “new star.”
Just a few decades later in 1604, Johannes Kepler saw a similar event in the constellation Ophiuchus and wrote about it in De Stella Nova in Pede Serpentarii—”The New Star in the Foot of the Serpent Bearer.”
But were these stars really “new”? Not quite. What Brahe and Kepler witnessed were powerful stellar explosions. And those have names. Let’s explore them.
A nova happens in a special kind of binary star system—where two stars orbit each other. One of them is a white dwarf, the remnant of a star like our Sun. Its companion is often a normal star or red giants. Over time, the white dwarf’s gravity siphons hydrogen gas from its companion, piling it onto the white dwarf’s surface like fuel on a hot plate.
When enough hydrogen builds up and the white dwarf’s surface gets hot enough, it ignites in a runaway fusion reaction—boom!—briefly making the system thousands of times brighter. This is what we call a nova.
The star isn’t destroyed. It survives. After days to months, the glow fades, and the cycle can repeat.
A nova is not the end of the star.
But some explosions are so massive, they don’t leave the star intact.
A supernova is a different beast: it’s the death of a massive star, and it’s far more energetic—often billions of times brighter than a nova.
These happen to a star more than 8 times the mass of our Sun. After fusing hydrogen into helium and helium into heavier elements, the star’s core eventually builds up iron.
Fusing iron doesn’t release energy—it costs energy—so the star can no longer support itself. Gravity wins, the star collapses in on itself in a fraction of a second, and a titanic shockwave blows the star apart.
What’s left behind is a neutron star—a city‑sized sphere of ultra‑dense matter—or sometimes a black hole. This is a Type II supernova.
And then there’s Type I supernovae—these involve white dwarfs too. If a white dwarf in a binary system steals enough mass from its partner and crosses a critical limit—1.4 solar masses known as the Chandrasekhar limit—it can no longer support itself and trigger a runaway fusion of carbon and oxygen throughout the entire star. The white dwarf is obliterated in a single, brilliant flash. Type Ia supernovae shine with remarkably uniform peak brightness, making them essential “standard candles” for measuring cosmic distances.
These are the events Brahe and Kepler saw centuries ago, bright enough to be seen in daylight.
Sometimes, a core‑collapse supernova goes even bigger. That’s where hypernovae come in.
These explosions are 100 times more powerful than supernovae. They happen when a truly massive star—over 30 times the mass of the Sun—collapses directly into a black hole.The energy released can launch intense gamma-ray bursts across the universe.
Some scientists believe these can also happen in double star systems where one neutron star gets “fed” by the remains of another star’s explosion. When that second star explodes, its material falls onto the neutron star and sets off an even more massive chain reaction.
If a supernova is a city’s fireworks show, a hypernova is the entire skyline lighting up at once.
Next up: kilonovae. These are cosmic collisions at their finest.
Picture two neutron stars—the ultra-dense leftovers from previous supernovae—or a neutron star and a black hole. After billions of years spiraling inward, they smash into each other and release gravitational waves—ripples in spacetime—and a burst of high‑energy radiation. The optical/infrared afterglow of that merger is called a kilonova.
A kilonova can be roughly a thousand times brighter than a nova, but generally dimmer and shorter‑lived than many supernovae. These mergers are cosmic alchemists: they forge heavy elements like gold and platinum via rapid neutron capture, then scatter that treasure into space to seed the next generation of stars and planets. Many short gamma‑ray bursts are tied to these dramatic mergers.
So yes, the jewelry you’re wearing may have come from the death throes of stars.
And finally, we have the tiniest star explosions of them all—micronovae. A localized explosions on the surface of magnetic white dwarfs in binary systems
Discovered recently, these happen on white dwarfs with extremely strong magnetic fields. As material from a companion star gets funneled toward the magnetic poles, a mini thermonuclear blast erupts—not across the whole surface like a regular nova, but just at the poles. These events last just a few hours and release only a millionth of the energy of a full nova.
Still, they’re powerful enough for astronomers to detect from light-years away. And so, we call them micronovae.
Stellar explosions are the Universe’s recycling program. Core‑collapse supernovae spread oxygen, calcium, and iron—the stuff of life and rocky worlds. Kilonovae mint the precious metals. Type Ia supernovae help us chart the expanding Universe. Even the smaller flashes—novae and micronovae—teach us how matter behaves under extreme gravity and magnetism.
From Tycho and Kepler’s “new stars” to today’s multi‑messenger astronomy—combining light, gamma rays, and gravitational waves—each kind of eruption reveals a different chapter in the life and death of stars.
So the next time you look up, remember: the quiet night sky is the aftermath of ancient fireworks, and the Universe is already planning its next show.
Until next time—and this is 365 days of astronomy
End of podcast:
365 Days of Astronomy
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The 365 Days of Astronomy Podcast is produced by Planetary Science Institute. Audio post production by me, Richard Drumm, project management by Avivah Yamani, and hosting donated by libsyn.com. This content is released under a creative commons Attribution-NonCommercial 4.0 International license. Please share what you love but don’t sell what’s free.
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As we wrap up today’s episode, we are looking forward to unravel more stories from the Universe. With every new discovery from ground-based and space-based observatories, and each milestone in space exploration, we come closer to understanding the cosmos and our place within it.
Until next time let the stars guide your curiosity