Jupiter and Saturn have not been so visibly close to 800 years: how to look

Saturn, captured here by the Hubble Space Telescope during the summer, will align with Jupiter on December 21st.

NASA, ESA, A. Simon (Goddard Space Flight Center), MH Wong (University of California, Berkeley) and the OPAL team

Get ready for a rare and spectacular sight just before Christmas. An event called a great conjunction will happen on December 21, when Jupiter and Saturn, the two largest planets in our solar system, appear very close to the sky. In fact, closer than they have since the Middle Ages.

The event is so legendary that some have associated it with the famous Star of Bethlehem who guided the three sages in the story of the Biblical Birth. (For more details on this angle, read below.)

In astronomy, a conjunction occurs when either of two astronomical objects (asteroids, moons, planets, stars) appear close to each other in the sky when observed from Earth. A large conjunction specifically involves Jupiter and Saturn. This only happens every 19.6 years, so the event is already rare, but the event of December 21 will be the closest observable conjunction between the two in 1226. (They also approached in 1623, but it probably couldn’t be seen from Earth.) And don’t miss it – you may not have another chance.

“This is the largest ‘big’ conjunction between Jupiter and Saturn for the next 60 years, with the two planets not appearing so close to the sky until 2080,” said Preston Dyches, a writer and producer at Jet Propulsion Laboratory. NASA, in a NASA Video.

The December 21 event should be easy to see, says astronomy educator and former planetarium director Jeffrey Hunt, who wrote about the event on his website, When the Curves Align.

“Go out after sunset to find (the planets) in the southern sky,” he advises. “A pair of binoculars is useful; the pair is visible to the helpless eye as Jupiter passes it and passes Saturn. On the evening of the conjunction, the planets fall into the eyepiece of an observation telescope or a small, low-power telescope.”

Saturn’s rings and Jupiter’s four brightest and largest moons will also be visible with binoculars or a telescope.

Those who want to photograph the moment can do so easily. Hunt says a tripod-mounted camera with exposures of up to 10 seconds can capture planets and background stars. The event should be visible from anywhere on Earth, offering clear skies.

The conjunction is sometimes called the Christmas star. Some claim that a similar planetary encounter created the legendary Star of Bethlehem that led the biblical Magi, also known as the three sages, to the Child of Christ. Even the German astronomer Johannes Kepler launched the idea in the 17th century.

But when you dig into the facts, that doesn’t quite fit.

“Everyone is looking for a fantastic angle,” says Hunt. “The problem with the connection of the Star of Bethlehem is the real year and the season (or) of the month of birth. And there are other planetary alignments that could explain the Star of Bethlehem. This subject has been beaten to the limit by the planetarium community. in the 1980s. “

Don’t look for a SF fusion with Jupiter and Saturn, says Hunt. This is not an eclipse.

“The planets will not merge into a single point of light, as reported in some media,” he says. In other words, Jupiter will not pass directly in front of Saturn, interrupting his sight.

You really don’t need to beautify your eyesight, because it’s amazing enough on its own.

Hunt observes that, although this special event is almost close, he realizes that an excellent conjunction is a generational event, not a unique one in life.

“A great conjunction occurs three or four times during human life and marks the passage of generations,” he says. “I encourage families to take their children outside to look, to tell their children that the planets will be next to each other again in 20 years, and I ask how old they will be then.”

Although the planets reunite in time, December 21 will mark the actual conjunction – the night when the two planets are closest, and Jupiter passes very slowly over Saturn. December 21, of course, also marks the winter solstice in the northern hemisphere and the summer solstice in the southern hemisphere.

If you are tied up on December 21, you can continue to go out until Christmas Eve to marvel at your sight. The planets will remain close until December 24.

Finally, 2020 gives us something positive to look forward to.