The solar system’s two largest planets — Jupiter and Saturn — are hundreds of millions of miles apart from each other. But from our vantage point on Earth, they appear to be very close to each other and getting closer.
And on Dec. 21, 2020, they’ll do a celestial dance no human has seen in centuries.
“They haven’t been this close together in about 800 years.” — Paulette Epstein, Michigan Science Center
It’s called the “great conjunction” because the gas giants will be so close together that, to the naked eye, they will almost appear to be a single object in the night sky. Paulette Epstein is the director of scientific partnerships at the Michigan Science Center in Detroit.
Click on the audio player to hear the Michigan Science Center’s Paulette Epstein describe the planetary conjunction of Jupiter and Saturn.
“They’re going to appear 0.1 degrees apart, or just about one-fifth the apparent width of the moon,” Epstein says.
The last time they appeared so close to each other was 1623, although they were so close to the sun, it’s unlikely that many people witnessed it, according to EarthSky. The last observable great conjunction happened in 1226.
“They haven’t really been this close together in about 800 years,” she says.
Epstein says the cool thing about this conjunction is that people who use a telescope or binoculars to view it will see both planets in their field of view — and more.
“You’d be able to see Jupiter’s four largest moons, and if you have a large enough scope, you’ll even be able to see the rings (of Saturn),” she says.
Conjunctions of this type are pretty common, occurring about 20 years apart. But if they’re too close to the sun or the horizon, they may be very difficult to see as clearly as this year’s event. The next best opportunity to see them this close will happen in March 2080. But if conditions are right, Epstein says you shouldn’t miss this one, which also coincides with the winter solstice.
“I do encourage everyone to go outside and take a look whenever it’s clear,” she says. “Because we know in Michigan, it’s pretty cloudy most of the time.”
And at this time of year, it’s pretty cold, too.