KIM JONG-BOOM
What is a hydrogen bomb, does North Korea have one and what is the difference between that and an atomic bomb?
RISING tensions on the Korean Peninsula have the world worried about North Korea - the secretive and totalitarian regime that claims to have detonated a hydrogen bomb.
Such a thermonuclear device - many times more powerful than an atomic bomb - can easily wipe out a major city. Here's what we know about Kim Jong-un's most powerful weapon yet...
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What is an atom bomb?
Atomic weapons make use of the huge amounts of energy released when atoms split - known as fission.
This process happens naturally in radioactive materials such as uranium and plutonium.
The large atoms break down into other elements, generating a burst of heat radiation equivalent to the difference in mass (using Einstein's famous E=mc2 formula).
Subatomic particles called neutrons are also released. If other neighbouring atoms absorb the neutrons they become unstable and split - creating a chain reaction of nuclear fission.
A controlled chain fission reaction can be safely harnessed in a power station to generate electricity.
In an atom bomb, conventional explosives are used to force fissile material into a "critical mass" at high temperature and pressure.
The result is an exponentially increasing chain reaction and the rapid release of vast amounts of energy.
The first A-bomb used in war - dropped by the US on Hiroshima on August 6, 1945 - generated a blast equivalent to around 15,000 tons (15 kilotons) of TNT explosives.
The second, at Nagasaki three days later, had a force of around 20 kilotons and killed an estimated 40,000 people in an instant as well as many more who died later from burns and radiation poisoning.
Later designs had a "yield" - explosive power - of up to 500 kilotons.
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What is a hydrogen bomb?
A more advanced and much more powerful type of weapon was developed after the Second World War, exploiting the energy released by nuclear fusion.
This is the process at the heart of stars like the sun in which atoms of the lightest element, hydrogen, are joined together to create helium.
The reaction can only occur at extremely high temperature and pressure.
Thermonuclear weapons use a fission device as a first-stage "trigger" to compress and heat the secondary stage containing the fusion fuel, isotopes of hydrogen.
The resulting blast is devastating with the power to flatten every building for miles.
The first fusion fuel staged thermonuclear bomb tested by the US had a yield of 10,400 kilotons - around 700 times more powerful than the Hiroshima bomb.
The Tsar Bomba, a three-stage hydrogen weapon tested by the Soviet Union in 1961, generated a blast of 500 megatons, equivalent to 500 million tons of TNT.
International treaties have led to a reduction in payloads in recent decades.
Britain's Trident II nuclear missiles each carry up to 12 lightweight W76 warheads. Each warhead weighs just 164kg (26 stone) and has a yield of 100 kilotons.
The most powerful weapon in the current US armoury is the B83, which is dropped by aeroplane and has a maximum yield of 1.2 megatons.
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Has North Korea tested a hydrogen bomb?
The pariah regime of Kim Jong-un was condemned across the world after conducting its sixth nuclear test at a heavily-protected underground testing facility in Punggye-ri.
North Korea claimed it was an advanced hydrogen bomb that is small and light enough to be delivered by one of its long-range missiles.
The country bragged the new weapons had "great destructive power" and have a yield that is adjustable from "tens to hundreds of kilotons" and can be detonated at high altitude.
It is not possible to verify whether North Korean scientists have successfully developed a thermonuclear bomb.
But seismic data showed the underground test triggered an earthquake of magnitude 6.3 - around ten times more powerful than the fifth test a year ago.
Norwegian scientists estimated the yield of the device at around 120 kilotons, six times more powerful than the test in September 2016.
North Korea also claimed that device was a hydrogen bomb - but that claim was widely dismissed by experts in the West who said it was almost certainly a fission bomb.
Thermonuclear weapons are more efficient but also far more technically difficult to make than A-bombs so it would be a major step for impoverished North Korea.
So far only five countries are confirmed to have tested hydrogen bombs - the USA, Russia, the UK, France and China. India's claim to have detonated a staged thermonuclear weapon is disputed.
It is also not possible to verify if North Korea has been able to miniaturise a nuclear device.
This is seen as a key step in developing nuclear weapons as it means bombs can be deployed by missiles, which are harder to intercept than planes.
Kim's generals have successfully launched a Hwasong-14 intercontinental ballistic missile over the Pacific and are said to be preparing more tests in a provocative challenge to the US.
If North Korea's boasts are true, potentially millions of people could be wiped out in cities as far away as Chicago.
The US THAAD missile defence system has been deployed in Alaska and South Korea ready to shoot down any rockets from the hostile state.
President Donald Trump reacted to the latest test by warning Kim of "total annihilation" if he threatens the US.
And he ominously warned "only one thing will work" when dealing with the rogue state.
South Korea is ready to launch "blackout bombs" to paralyse North Korea’s power grid in the event of a nuclear war.
Most recently, a North Korean official has warned that Kim Jong-un's hydrogen bomb threat should be taken 'literally'.
The North Korean leader recently warned through his foreign minister of a possible atmospheric nuclear test over the Pacific Ocean.
Nuclear war may break out any moment' North Korean Deputy Ambassador delivers warning at United Nations
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