See an ultra-rare space event, or wait for 2080
An astronomical tension has been building in the evening sky this month. The two largest planets, Jupiter and Saturn, have been getting closer to each other after sunset. And on Dec. 21, they will appear so close together in the sky that you will be able to see them both in a telescope at the same time.
A space rarity
Jupiter and Saturn cozy up to one another about every 20 years. This is called a Great Conjunction. But this year’s conjunction will put the two planets closer together than they have been since 1623.
The two planets will only seem close to each other, but are millions of miles apart. Jupiter will be about 550 million miles from Earth while Saturn will be about one billion miles away. The two just happen to line up from our view as they circle the sun at different distances and different speeds.
How close will they get?
The two planets will not be close enough to merge into one brilliant point of light. Stargazers with good or average eyesight should be able to detect them as two separate objects with the naked eye. Jupiter, which is several times brighter than Saturn, will attract your attention. It may take a moment for you to spot dimmer Saturn just to Jupiter’s right. At first glance, it may look like Jupiter has a small bump on it. That’ll be distant Saturn.
When you look through even a backyard telescope, you will be able to see Jupiter and its moons and Saturn and its rings. Jupiter will look like a small disc with two or more stripes (showing the storms of the gas giant planet). Jupiter’s moon Europa will look like a little star to one side of the planet while Ganymede, Io and Callisto will spread out as dots on the other side.
Saturn will be near Jupiter with its rings tilted slightly askew. The disc of Saturn will appear smaller than Jupiter, but its rings extend enough to nearly
double its size. If sky conditions are good, you may also see Saturn’s largest moon, Titan, and three smaller moons Rhea, Dione and Tethys.
Between 6:15-6:45 p.m. on Dec. 21, face southwest. There, you will easily spot Jupiter as one of the brightest nighttime objects. Saturn will be the fainter pinpoint of light to Jupiter’s right.
The planets will be low in the sky, so you will need to view from a location with a clear view to the southwestern horizon.
Although Jupiter and Saturn will appear nearest on the evening of Dec. 21, they will be very close together Dec. 18-24. In fact, you should also be able to see them simultaneously in a small telescope on Dec. 20, 21 and 22.
For most people, this will be the only nights in your life where you can see Jupiter and Saturn in a telescope at the same time. The next Jupiter-Saturn conjunction this good will not happen again until 2080.
Dean Regas is the Astronomer at the Cincinnati Observatory and author of 100 Things to See in the Night Sky, Expanded Edition. He can be reached at firstname.lastname@example.org
Constellation Myths -Online Classes
Learn the ancient tales behind your favorite constellations including Orion the Hunter and the Seven Sisters, Taurus the Bull, the Big and Little Dogs, and more. Astronomer Dean Regas puts a new spin on these myths and shows you where to find the constellations in the sky for yourself.
When: Dec. 22, 7 p.m. - Adult Version.
Dec. 23, 7 p.m. - Family Friendly Version
Where: Online class Cost: $10 per household More Info: cincinnatiobservatory.org