Physics

What's A Hydrogen Bomb, And Should We Be Worried If North Korea Has Tested One?

January 6, 2016 | by Jonathan O'Callaghan

Photo credit: Wasan Ritthawon/Shutterstock

Today, it has been widely reported that North Korea apparently detonated a hydrogen bomb near the Punggye-ri nuclear site in the northeast of the country.

"The first H-bomb test was successfully conducted at 10 o’clock [local time, 4 a.m. GMT] on January the 6th 2016," North Korea's state news network reported. "We will not give up a nuclear programme as long as the United States maintains its stance of aggression."

While the veracity of the country’s claim that it was a hydrogen bomb is debatable, the fact that detected seismology readings of 5.1 were caused by an explosion – and not a natural event – are widely agreed.

The action, whatever it was, has been widely condemned. Even China, once regarded as North Korea’s closest ally, said it "firmly opposed" the test. Japan said it was a "major threat" to its national security.

This would be North Korea’s fourth nuclear bomb test, following tests in 2006, 2009, and 2013. But what do we actually know about this latest one and what does it mean? Let’s take a look.

What is a hydrogen bomb?

A "regular" atomic bomb, like the ones dropped on Hiroshima and Nagasaki, uses nuclear fission to split atoms and produce energy. Upon detonation, this energy is released, resulting in a large explosion.

Hydrogen bombs, on the other hand, come in a variety of configurations. Also known as a thermonuclear bomb, they generally involve a layered system where one explosion triggers another – such as nuclear fission and nuclear fusion, the latter of which occurs in the Sun.

In one type of hydrogen bomb, the fission reaction emits X-rays that trigger the fusion of two hydrogen isotopes, tritium and deuterium. This in turn triggers an enormous release of energy. They are considerably more powerful than atomic bombs.

How do we know they detonated a bomb?

We know thanks to seismology readings from various seismometers around the world. These are able to detect waveforms from large seismic events. In this case, the waveform started abruptly and then faded, consistent with an explosion – and not a natural event like an earthquake.

Was this definitely a hydrogen bomb?

No. The seismology readings, between 4.9 and 5.1, are consistent with their previous tests, which were plutonium bombs. North Korea, though, claims this was a "miniaturized" hydrogen bomb.

However, some experts have been very sceptical of the claims. "The bang they should have gotten would have been ten times greater than what they're claiming," said Bruce Bennett, an analyst with the Rand Corporation, reported the BBC.

"So Kim Jong-un is either lying, saying they did a hydrogen test when they didn't, they just used a little bit more efficient fission weapon – or the hydrogen part of the test really didn't work very well or the fission part didn't work very well."

Would this be their first hydrogen bomb?

If confirmed, then yes. The other three tests were plutonium, i.e. regular atomic bombs.

What could North Korea do with it?

If it is a miniaturized bomb, it would be possible for them to put the bomb on a missile. Of course, it’s pretty unlikely they’d do this. This latest test was likely just meant as a show of power to the rest of the world.

What will happen now?

It’s unclear. Countries including South Korea and the U.S. will hold emergency meetings. It’s likely that further sanctions will be placed on North Korea.

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