Watch: Jupiter and Saturn to align in the sky tonight
The sky tonight will offer a Christmas feast of celestial treats for stargazers, with both a planetary conjunction described as a “Christmas star” and a meteor shower.
Not only do the events coincide with a first quarter moon, but there should be lots of dark hours for stargazing as it’s also the winter solstice.
Sky-watchers should be able to see a conjunction between Jupiter and Saturn and possibly meteors from the Ursid meteor shower.
Once every two decades, the two largest planets in our solar system appear to meet in Earth’s skies, in what is known as the “Great Conjunction”.
Some experts have suggested the bright light of the conjunction may be behind the Bible story of the Star of Bethlehem.
Weather permitting, Jupiter and Saturn will look like two bright stars that are almost touching, as seen by the human eye.
Dr William Teets, director of Vanderbilt University’s Dyer Observatory writes on The Conversation: "If you have a pair of binoculars, you’ll easily be able to spot both planets. In even a small telescope, you’d see both planets at the same time in the same field of view, which is really unheard of.
“That’s what makes this conjunction so rare. Jupiter and Saturn appear to meet up about every 20 years. Most of the time, however, they’re not nearly as close together."
This year, the conjunction will be far closer than normal: the two gas giants will be only 0.1 degree apart (1/5th the diameter of the full Moon).
It’s the closest the two planets have come to each other in the sky since the Great Conjunction of 1623.
The Ursid meteor shower will also be visible: it’s expected to peak some time during the night of 21 December and will be visible until the early morning of 22 December.
This celestial display is associated with the comet 8P/Tuttle, also known as Comet Tuttle, which orbits the Sun once every 13 years.
Royal Observatory Greenwich writes: “The Ursid meteor shower is usually sparse, producing around five meteors per hour at its peak. The Moon will be in its first quarter phase during the shower's peak this year, so at least the Moon's light won't obscure your view of the night sky.
“Ursids meteors appear to radiate from near the Beta Ursae Minoris (Kochab) in the constellation Ursa Minor.
“However, the actual source of the shooting stars is a stream of debris left behind by comet 8P/Tuttle.”
Read more: Astronomers find closest black hole to Earth
A telescope under high magnification will reveal the cloud belts of Jupiter and the rings of Saturn, as well as several of their moons, all at the same time.
Lowell Observatory in Flagstaff, Arizona, will be covering the Great Conjunction with a free interactive livestream program on YouTube..
To see it from Britain, you might have to wait until the sun goes down, warn experts from Sky At Night magazine.
Jamie Carter of Sky at Night magazine writes: “The main event will have Jupiter and Saturn separated by a mere 0.06′ – 6 seconds of arc – at 13:30 Universal Time on Monday, 21 December, 2020. That’s 13:30 GMT, so during daylight hours in the UK.
“Sunset will take place at 15:53 in London, 16:06 in Cardiff, 15:59 in Belfast and 15:39 in Edinburgh. About 45 minutes after sunset observers should look 10º above the south-southwest horizon to see Jupiter and Saturn shining almost as one.”
Watch: Astronaut shows glimpse of earth from space