An asteroid strike on Earth is just a matter of time, a leading astrophysicist from Queen’s University Belfast has warned, reports said on Tuesday. It is more a case of when an asteroid collision will happen, rather than if it will happen, said Professor Alan Fitzsimmons from the University’s Astrophysics Research Centre.

The warning comes ahead of Asteroid Day, which is on June 30. A small asteroid had exploded over Tunguska in Russia’s Siberia on that day in 1908. The asteroid had levelled trees and burned ground covering over 2,000 square kilometres, the report said.

“It is important to know that scientists and engineers have made great strides in detecting Near-Earth Asteroids and understanding the threat posed by them. Over 1,800 potentially hazardous objects have been discovered so far, but there are many more waiting to be found,” Professor Fitzsimmons said.

He said that a major city could be destroyed in a similar unexpected strike in today’s world. A larger asteroid could be far more dangerous, he warned.

“Astronomers find Near-Earth Asteroids every day and most are harmless. But it is still possible the next Tunguska would take us by surprise, and although we are much better at finding larger asteroids, that does us no good if we are not prepared to do something about them,” he said.