Jupiter and Venus - the two brightest planets - have been appearing together in the morning sky.
They have been visible to the naked eye across the UK and countries in the mid-northern latitudes, including parts of the US.
Experts said they were so close as to appear almost on top of each other, perhaps looking like one bright star.
In the UK the best viewing time was 40 minutes before sunrise, but the planets began appearing before dawn.
While the planets have been visible to the naked eye, viewers with a telescope have also been able to see Jupiter's four Galilean moons.
People in the UK have taken to social media to share their photos of the planetary display.
Viewed from London, the planets began appearing shortly before 06:00 GMT with conjunction occurring just after.
Observers have had an uninterrupted view to the South East as the planets have been very low in the sky. Those on high ground have had the best chance of seeing the conjunction.
Robert Massey, acting executive director of the Royal Astronomical Society, said binoculars afforded a better view before the sun rises above the horizon but warned people not to do this after sunrise, as it could be dangerous.