British astronaut Major Tim Peake has apologised for dialling a wrong number and saying: "Hello, is this planet Earth?"
On board the International Space Station, Major Peake insisted that he was not playing a joke on the woman he rang by accident.
He tweeted: "I'd like to apologise to the lady I just called by mistake saying 'Hello, is this planet Earth?' - not a prank call ... just a wrong number!"
Meanwhile, flying low over the rooftops, it could easily be mistaken for Santa's sleigh.
But the bright light that could be seen crossing the sky after sunset on Christmas Day is the International Space Station, soaring 250 miles over the French-Spanish border.
From southern England, it will appear in the West at about 4.24pm and remain visible for six minutes before disappearing below the south-eastern horizon.
On board, Major Peake and the rest of the crew will be treated to a spectacular sight as their orbiting craft flies over the "Christmas lights" of European cities and towns after sunset.
Robin Scagell, vice-president of the Society for Popular Astronomy, said: "The space station's maximum elevation will be about 23 degrees viewed from London, which is just above the rooftops.
"It will be the brightest star in the sky, moving rapidly from west to east. You might think it's a plane to start with, but you'd hear the engine noise of an aircraft that close and of course the space station is silent.
"So we'll be able to see a different object flying over the rooftops on Christmas Day."
Viewed from further north, the space station will appear lower in the sky, but should still be visible from the north of Scotland. Seen from south-west England, it will have a higher elevation of around 30 degrees.
A full moon is also due make an appearance on Christmas Day, but it is not due to rise until the International Space Station has completed its journey.