An asteroid the size of four football pitches is due to fly past Earth.
However scientists insist there is no need to be scared on Halloween night - as it will remain further away than the moon.
It is being called the "Great Pumpkin" by astronomers but is expected miss the planet by 300,000 miles (around 480,000 kilometres).
The flyby will take place at around 5pm Irish time.
The asteroid - officially named NEO 2015 TB 145 - measures 280 to 620 metres in diameter and is moving at a velocity of 35km/s, which NASA scientists describe as “unusually high.”
NASA researchers have determined "that the celestial object is more than likely a dead comet that has shed its volatiles after numerous passes around the sun".
After the Halloween visit, no – as yet – known object will come as close to the Earth again until August 2027, when NEO 1999 AN10 will be at 1.0 lunar distance.
During the flyby, the asteroid will reach a magnitude luminosity of 10, so it should be observable to astronomers with telescopes, particularly those situated in the Northern Hemisphere.
