The risk is growing that Earth will be hit by an asteroid from a meteor stream known as the Taurids, Czech astronomers said on Tuesday.
The astronomers, from the Czech Academy of Sciences, drew their conclusion after analysing 144 bolides -- large meteors that explode in the atmosphere -- from the Taurids and detecting a new branch with at least two asteroids measuring 200-300 metres (220-330 yards) in diameter.
"Most probably, the branch also includes many undetected asteroids which are dozens of metres in diameter or larger," the Czech academy said in a press release.
"Hence, the danger of a crash with an asteroid grows markedly once every few years that the Earth encounters this stream of inter-planetary material."
The new branch comprises objects moving together around the Sun, and the Earth encounters it once every few years for a period of about three weeks.
"During this period, the probability of a collision with a larger object (of about dozens of metres in diameter) is markedly higher," the Academy said.
The asteroids are very fragile, but when they are this large they may penetrate deep into the atmosphere and pose a real threat of collision with Earth, it added.
The study urges further research to obtain "a better description of this real source of potentially hazardous objects large enough to cause a local or even continental disaster."
The paper is available on the Astronomy & Astrophysics website (https://www.aanda.org/component/article?access=doi&doi=10.1051/0004-6361/201730787) pending publication in its renowned journal.