Stargazers’ attempts to observe a once-in-a-lifetime sight were hindered in the UK by a far more everyday occurrence – bad weather.
Many hoping to see the “great conjunction” of Jupiter and Saturn on Monday evening, where the two planets appeared closer together in the night sky than they have for almost 400 years, were disappointed when their view was obscured by clouds.
The alignment of the two bodies was supposed to mean they appeared as one bright star shortly after sunset. Astronomers said the two should still be near enough to each other over the coming nights to enjoy the spectacle, even though 6.37pm GMT on Monday was the point when they were closest.
A small crowd gathered at a single large block of sarsen stone standing outside the entrance of the Stonehenge earthwork in Wiltshire to watch the phenomenon and to mark the shortest day of year, despite English Heritage cancelling this year’s winter solstice celebrations due to the pandemic.
Conjunctions of Jupiter and Saturn take place every 20 years, but many are impossible to see with the naked eye because they happen during the day, or are less impressive as the planets do not come as close. This time the planets were just one-tenth of a degree apart from the Earth’s perspective, or about one-fifth the width of a full moon. It is also the first time for 800 years it has occurred so near to Christmas.
Wilf Somogyi, who is in the astrophysics group at UCL, had been hoping to see the configuration on Monday but said that from Cambridge it was too cloudy. “I cannot see anything at all, which is a bit of a shame, but there will be another one in 60 years I guess,” he said.
“I had a look at the cloud coverage map and it looks like everywhere is covered in a cloud this evening. It could be seen last night and the planets will still be close together for the next few nights. Some people may have seen it last night. There are other opportunities. They get close together and reach their closest point and then separate.”
Somogyi added:“It’s a rare appearance. The last one was about 400 years ago but it was not visible to everyone, only places closest to the equator.”
David Weintraub, an astronomy professor at Vanderbilt University, said: “I think one thing that is a bit misleading for people is, well there has been so much interest in tonight as this is when they are officially at conjunction, so closest together. But with the naked eye, without a telescope, they are not going to be further apart when you see them tomorrow. So if it is cloudy or the weather is poor, you can go out another night and it won’t look any different.”
He said he saw the configuration on Sunday and it appeared as two dots in the sky. “Jupiter orbits the sun in 12 years and Saturn 29 years, so Jupiter laps Saturn … a conjunction like this happens every 20 years, but some of those conjunctions happen when Jupiter and Saturn are further apart, so then it does not look like a double star.
“It’s a once-in-a-lifetime event but it’s not fireworks, it’s just two things that look like stars in the sky.”
• This article was amended on 23 December 2020. In an earlier version it was incorrectly stated that Saturn orbited the sun every 60 years.