North Korea’s nuclear weapons are about 10 times more powerful than the atomic bomb dropped on Hiroshima, satellite images suggest.

Leader Kim Jong-un recently pledged to suspend the country’s nuclear program , but little is known about its existing arsenal.

To search for clues, Teng Wang at Nanyang Technological University in Singapore and his colleagues studied German satellite images of North Korea’s Punggye-ri nuclear testing site at Mount Mantap. Six nuclear tests have been conducted inside this mountain since 2006.

They were particularly interested in …