(CNN)Sticking it to its foes, North Korea on Wednesday celebrated what it called a successful hydrogen bomb test -- a milestone that, if true, marks a colossal advancement for the reclusive regime and a big test for leaders worldwide to determine what to do about it.
"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!" read a document signed by North Korean leader Kim Jong Un on state television.
Pyongyang has been very vocal about its nuclear ambitions, pressing on despite widespread condemnation, sanctions, and other punishments. Having a hydrogen bomb -- a device far more powerful than the plutonium weapons that North Korea has used in three earlier underground nuclear tests -- ups the ante significantly.
Still, is this boast legitimate? The purported underground test, which happened at 10 a.m. (8:30 p.m. ET Tuesday), corresponded with a magnitude 5.1 seismic event centered 12 miles (19 kilometers) east-southeast of Sungjibaegam, according to the U.S. Geological Survey. That's comparable to readings from North Korea's most recent plutonium test in 2013.
Norsar, a Norway-based group that monitors nuclear tests, noted both facts and estimated, based on the seismic readings, a blast equivalent to less than of 10,000 tons of TNT -- smaller than those of the atomic bombs used on Hiroshima and Nagasaki, and far less than thermonuclear weapons that typically are as potent as millions of tons of TNT.
"We won't know for another few days or weeks whether this was (a hydrogen bomb)," said Martin Navias, a military expert at King's College London. "It doesn't look like one; ... one would have expected it to be greater if it was an H-bomb."
An answer may be found in U.S. or South Korean analysis of the atmosphere for "trace elements [of] radiation," though Mike Chinoy, a fellow at the University of Southern California's U.S.-China Institute, noted that "we may never know 100%."
