The Sun and a Thermonuclear Explosion: How They're Alike

October 21,2013

 

 

 

 

Thermonuclear warheads are among the most feared man-made devices on Earth. For decades, they’ve been used to showcase military might and act as a deterrent of aggression from other nuclear-armed nations. For many, the power of a nuclear weapon is incomprehensible.
The largest nuclear weapon ever detonated was the Tsar Bomba, and it was developed by the Soviet Union in the early 1960s. According to a PBS article from 2011, the bomb was 50 megatons. The bomb had 10 times the power of all the bombs used during Word War II.

Tsar Bomba Fireball

The Tsar Bomba, a secret Soviet nuclear weapon, was the largest thermonuclear device ever detonated. It had a fireball about five miles wide and the shockwave reverberated around the Earth at least three times. (El C/Wikimedia)

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During detonation the fireball was estimated to be about five miles in diameter, about half the length of Manhattan Island in New York City. The image at the right, taken by the Soviets, shows the enormity of the fireball. It looks a lot like the sun -- and there’s a reason for that.
The sun’s energy engine is essentially a perpetual thermonuclear explosion, just on a much larger scale. Just to give you a bit of perspective, the Tsar Bomba released about 2.1x1017 Joules of energy, while the Earth receives about 1.7x1017 Joules of energy from the sun in a second. So it’s safe to say the sun’s energy output dwarfs even the largest thermonuclear bomb detonations.
But what causes these sun’s massive releases of energy? In a word: fusion. In both a warhead and the core of the sun, hydrogen atoms are fused together under enormous pressure. The process of hydrogen fusion expels huge amounts of energy and forms another element, helium, a common thread for both. But the means by which fusion is initiated is completely different between the two.
In a thermonuclear device, there are two kinds of charges: the primary and the secondary. The primary charge is a fission device, meaning it splits atoms to produce energy. The heat and energy from the primary charge is used to detonate the secondary charge, which contains materials for fusion. The fusion of the materials in the second device causes a much larger explosion and produces the massive fireball we see in old pictures.

The Sun Releasing a Solar Flare

This is an image of an M-class flare captured by NASA scientists on May 3, 2013. (NASA)

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The sun, on the other hand, isn’t just a single nuclear explosion; it’s a perpetual series of them. At the sun’s core, hydrogen is being turned into helium. And just like in a nuclear bomb, massive amounts of energy are being released, but all that energy is self-contained due to the sun’s mass and enormous gravitational pull. 
After energy is produced in the sun’s core, it can take up to 100,000 years to reach the surface. Once it’s in space, it only takes that energy about eight minutes to travel the 93-million miles to the Earth’s surface.
So if anyone asks if you’ve ever seen a thermonuclear explosion, you can look to the sky and say, “I just did.”

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Nuclear Explosions

Nuclear Bomb Test, Nevada, August 18, 1957. (Image: Getty Images)