Jupiter-Saturn Great Conjunction: Watch Best View Since Middle Ages!

by Lance D. Davis


Stargazers get ready for a nice treat as we are about to witness a super-rare planetary alignment not seen for almost 800 years!

Our solar system’s two biggest worlds – the mighty Jupiter followed by the glorious ringed Saturn – will appear in the sky next to each other at their closest since 1623 and closest visible from Earth since the Middle Ages in 1226. This will happen on Dec. 21, 2020, during an event called a “great conjunction.”

Astronomers use the word conjunction to describe close approaches of planets and other objects on our sky’s dome. They use great conjunction specifically for Jupiter and Saturn because of the planets’ top-ranking sizes.

view of the 2020 great conjunction through the naked eye just after sunset
A graphic made from a simulation program, showing a view of the 2020 great conjunction through the naked eye just after sunset at approximately 5:15 p.m. (EST) on Dec. 21.
Credit: NASA

Great conjunctions between Jupiter and Saturn happen every 20 years, making the planets appear to be close to one another. This closeness occurs because Jupiter orbits the Sun every 12 years, while Saturn’s orbit takes 30 years, causing Jupiter to catch up to Saturn every couple of decades as viewed from Earth.

The last conjuction between these planets took place on May 28, 2000. This year’s conjunction occurs on Dec. 21, which coincidentally is also the date of the winter solstice in the Northern Hemisphere. The 2020 conjunction is unique because of how close Jupiter and Saturn will appear. In most conjunctions, Jupiter and Saturn pass within a degree of each other. This year, they will pass 10 times closer to each other – the closest in nearly 400 years.

view of the 2020 great conjunction through a telescope
A graphic made from a simulation program, showing the view of the 2020 great conjunction
through a telescope at approximately 5:15 p.m. (EST) on Dec. 21. Credit: NASA

Currently, you can watch Jupiter and Saturn get closer in Earth’s sky each evening until their grand finale on Dec. 21. Just look for them shortly after sunset, shining brightly and low in the southwestern sky. Also, tune in to NASA Science Live or NASA Facebook on Dec. 17 at 3:00 p.m. EST (2:00 p.m. CST) and learn how to see Jupiter and Saturn’s great conjunction.

During the great conjunction, the giant planets will appear just a tenth of a degree apart – that’s about the thickness of a dime held at arm’s length! This means the two planets and their moons will be visible in the same field of view through a small telescope. Truly, this is a once-in-a-lifetime event!

Some astronomers suggest the pair will look like an elongated star and others say the two planets will form a double planet. To know for sure, we’ll just have to look and see. Either way, take advantage of this opportunity because Jupiter and Saturn won’t appear this close in the sky until 2080!

Additional Information & Resources:

Learn how to photograph the Jupiter-Saturn conjunction.
Read about mission visits to Jupiter and Saturn.
Find an astronomy club or event near you!

Sky Watching Highlights for December 2020

In the month of December, stargazers get ready for some excitement in the sky! Catch the year’s best meteor shower, the Geminids, in the middle of the month. Then, witness an extremely close pairing of Jupiter and Saturn that won’t be repeated for decades. And mark the shortest day of the year on the northern winter solstice. Check out the video below produced by NASA’s Jet Propulsion Laboratory to learn more!

Sky Watching Highlights for November 2020

Are you ready for November’s sky watching highlights? Cool autumn evenings are a great time to look for the Pleiades star cluster. You’ll also have a couple of great opportunities to observe the Moon with Jupiter and Saturn. Plus, check out the phenomenon known as Earthshine. Learn about all that and more from NASA’s Jet Propulsion Laboratory’s video below!

Five Planets Align in Early Morning Sky

The graphic below illustrates the five planets as they are visible, with the naked eye, from Huntsville, Alabama.  It shows their positions in the sky around 6:30 AM during the week of January 18 and continuing for the next few days. Mercury will be close to the Sun, over in the East, and Jupiter will be over in the West, with Venus, Saturn, and Mars between the two. Pluto is near Mercury, but is invisible to the eye, requiring a telescope for viewing.

The last time an alignment such as this occurred was about 10 years ago. This pre-sunrise configuration will be similar for other northern latitudes.

In the graphic, the yellow line is the ecliptic, which is the plane of the Earth’s orbit. The orbits of the major planets lie close to this plane, which is why they appear close to the ecliptic in the night sky.

Image generated by Bill Cooke using SkySafari Pro software.
Image generated by Bill Cooke using SkySafari Pro software.

Jupiter and Venus Conjunction

On Tuesday, June 30, there will be a conjunction of Jupiter and Venus. A conjunction is a celestial event in which two planets or a planet and the moon or a planet and a star appear close together in the night sky. Conjunctions have no real astronomical value, but they are nice to view. While conjunctions aren’t as rare as one might think, this conjunction of Jupiter and Venus will be more impressive than most.

The casual backyard observer may have noticed that these two planets have been moving closer together for the past few weeks. On June 30, they will be so close that one will be able to hold a finger up and cover both Jupiter and Venus at the same time. In reality, the planets are hundreds of millions of miles apart. On June 30, Venus is about 46 million miles from Earth, and Jupiter is 560 million miles from Earth. Looking up at the sky, Venus appears to be much brighter than Jupiter. That is only because Venus is so much closer to Earth. Jupiter, the largest planet in our solar system, is actually over 11 times bigger than Venus, but it is dimmer when looking at the sky because of its great distance from our planet.

Typically the best conditions for stargazing involve a dark sky, so getting away from urban areas will make stars and faint objects like nebulae and galaxies more visible. The Jupiter and Venus conjunction will be easily bright enough to see from any location, even large cities. The best hours for viewing will be during evening twilight and up until 10:30 PM local time, when the planets will set behind the western horizon.cooke

'Only' 14 Million Miles Away!


The skies were clear over New Mexico last night — Oct. 6, 2010 — so Rhiannon Blaauw of NASA’s Meteoroid Environment Office, Marshall Space Flight Center, Huntsville, Ala., captured this image of Comet Hartley 2 at a distance of “only” about 14 million miles from Earth.

Hartley 2 has passed out of the constellation Cassiopeia and is now traveling through the constellation Perseus. On October 20th, the comet will come within 11 million miles of Earth. Since comets rarely come this close, it will be faintly visible to the naked eye in the early morning sky. The comet has an orbital period — or time to travel once around the sun — of approximately 6.5 years.

For those interested in astronomy photography, the image was taken with a single shot color filter with 300-second exposure via a remote-operated telescope located in Mayhill, N.M.

We’re tracking Hartley 2’s journey as it approaches Earth, so stay tuned for more photos!

Image courtesy of Rhiannon Blaauw, NASA’s Meteoroid Environment Office, Marshall Space Flight Center, Huntsville, Ala.

Comet Hartley 2 Seen in Cassiopeia

 
In this image taken on the evening of  Friday, Oct. 1, Comet Hartley 2 can be seen in the constellation Cassiopeia (north-east sky, not far from horizon).


Hartley 2 will only be in Cassiopeia for a few more day before traveling through the constellation Perseus. It’s a Jupiter Family Comet that we can’t see right now because it’s too tiny at approximately 1.2 km across. In this image, the comet was still 16,500,000 miles from Earth. 

On October 20th, Hartley 2 will will come within 11 million miles of Earth, and since comets rarely come this close, it will be visible to the naked eye in the early morning sky. The comet has an orbital period, or time to travel once around the sun, of approximately 6.5 years.

For those interested in astronomy photography, the image was taken with a single shot color filter with 300-second exposure. It was captured by Rhiannon Blaauw of NASA’s Meteoroid Environment Office, Marshall Space Flight Center, Huntsville, Ala., via a remote-operated telescope in Mayhill, N.M.

We’ll be keeping an eye on Hartley 2 as it approaches Earth, so stay tuned for more photos!


Images courtesy of Rhiannon Blaauw, NASA’s Meteoroid Environment Office, Marshall Space Flight Center, Huntsville, Ala.