(CNN)North Korea's announcement that it successfully conducted a hydrogen bomb test caught the world by surprise -- and raised a slew of questions about what this disturbing development means.
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North Korea nuclear bomb test: 7 key questions answered
Here are the answers to seven key questions:
A hydrogen bomb is much more powerful -- more powerful than anything North Korea has tested before.
The tests North Korea conducted until now used fission weapons, which break large atoms like plutonium, into smaller atoms. Such weapons can have a devastating impact. Think the atomic bombs that devastated Hiroshima and Nagasaki in 1945.
But hydrogen bombs use fusion, which take small atoms -- such as hydrogen -- and combine them. The result: a bomb that is hundreds of times more powerful than an atomic bomb.
Here's why: In order to combine the small atoms and start a fusion reaction, such a bomb needs a large amount of energy. And that energy comes from an atomic bomb inside the hydrogen bomb.
So, basically, a hydrogen bomb causes two separate explosions.
Boosting nuclear capability has been one of the hallmarks of North Korean leader Kim Jong Un's rule, said Mike Chinoy, author of "Meltdown: The Inside Story of the North Korean Nuclear Crisis."
"I think it does send a signal, again, that the North Koreans are a power to be reckoned with, and they want the rest of the world to take them seriously," Chinoy said.
In a signed letter broadcast on Korean media, Kim wrote that he wanted to ring in the new year with, quite literally, a bang.
"For the victorious and glorious year of 2016 when the 7th convention of the Workers' Party will be held, make the world look up to our strong nuclear country and labor party by opening the year with exciting noise of the first hydrogen bomb!" the letter read.
Maybe not, some analysts say.
"North Korea appears to have had a difficult time mastering even the basics of a fission weapon," wrote Bruce Bennett, a senior defense analyst at the Rand Corp, in a piece for CNN.com last month.
Bennett's piece came shortly after North Korean leader Kim Jong Un claimed last in December that his country had become a "powerful nuclear weapons state ready to detonate a hydrogen bomb."
"With this in mind, it is quite possible that Kim's claim could be untrue, which would come as no surprise to those familiar with the regime's saber rattling."
The U.S. said it could take days to confirm whether North Korea successfully tested a hydrogen bomb.
It's possible North Korea has a "boosted" weapon -- one that uses a small amount of fusion to boost the fission process, but is not a hydrogen bomb.
But even a boosted weapon could cause serious destruction.
"If North Korea really has a boosted nuclear weapon of perhaps 50 kilotons, it could do significant damage in a city as densely populated as Seoul, South Korea: About 250,000 people could be killed in such a strike, or about 2.5% of the population," Bennett wrote last month.
"And if North Korea one day produces a true hydrogen bomb of, say, one megaton yield, then it would be deadlier still."
A megaton is equal to 1 million tons of TNT.
Analysts have said that North Korea may be able to fit nuclear warheads on ground-launched missiles that can reach South Korea and Japan.
David Albright, a former U.N. weapons inspector, told CNN last year that Pyongyang could have 10 to 15 nuclear weapons and that it could grow that amount by several weapons per year.
Albright said he thinks Pyongyang can miniaturize a warhead for shorter missiles, but not yet for intercontinental ballistic missiles, or ICBMs.
An H-bomb test presents a serious dilemma for world leaders.
"All the choices with North Korea are bad," Chinoy said.
"There's no evidence that the sanctions that have been in place in one form or another for many, many years have had any impact on North Korean behavior, even if they have hurt the North Koreans to some degree economically. So a ratcheting up of sanctions is unlikely to have the desired effect."
And starting a war, of course, would be extremely dangerous.
"And that really only leaves talking to North Korea, which clearly, I think the North Koreans would like," Chinoy said.
Yun said the test could make North Korea feel more secure and emboldened in trying to negotiate on the world stage.
"They maybe feel like they're in a position of strength and be willing to have some kind of negotiation," he said.
"And obviously, from our standpoint, we have a lot less leverage."