[ad_1]
On December 21, 2020, the two gas giants of the solar system will appear closer to each other in Earth’s night sky than they have been since 1226 CE.
Jupiter and Saturn have crossed the skies together all year round, but in December be prepared for them to really put on a show. In the first three weeks of the month, watch each evening as the two planets move closer to the sky than they’ve appeared in two decades. Look for them down in the southwest within an hour of sunset, Image Credit: NASA / JPL-Caltech.
On December 21, Jupiter and Saturn will only appear within a tenth of a degree from each other. This means that the two giant planets and their moons will be visible in the same field of view through binoculars or a small telescope.
In fact, Saturn will appear as close to Jupiter as some of Jupiter’s moons. This event is called a “great conjunction”.
These occur every 20 years this century as the orbits of Earth, Jupiter, and Saturn periodically align, causing these two outer planets to appear close to each other in our night sky.
Even so, it is the “ greatest ” large conjunction between Jupiter and Saturn for the next 60 years, with the two planets not appearing as close in the sky as in 2080.
“Alignments between these two planets are rather rare, occurring once every 20 years or so, but this conjunction is exceptionally rare due to the closeness of the planets to each other,” said Professor Patrick Hartigan, astronomer at Rice University.
“We would have to go back to dawn on March 4, 1226 to see a closer alignment between these objects visible in the night sky.
“On the evening of the closest approach on December 21, they will look like a double planet, separated only by 1/5 the diameter of the full moon,” he added.
“For most viewers, each planet and several of their largest moons will be visible in the same field of view that evening.”
Jupiter and Saturn will appear low in the western sky for about an hour after sunset each evening.
“The farther north a viewer is, the less time they will have to see the conjunction before the planets sink below the horizon,” said Professor Hartigan.
Fortunately, the planets will be bright enough to be seen at dusk, which may be the best time for many American viewers to observe the conjunction.
“By the time the sky is completely dark in Houston, for example, the conjunction will be just 9 degrees above the horizon.”
“It would be manageable if the weather permitted and you had a clear view to the southwest.”
“But an hour after sunset, people who look up to the sky in New York or London will find the planets even closer to the horizon, about 7.5 degrees and 5.3 degrees, respectively.”
“Viewers there, and in similar latitudes, would do well to catch a glimpse of the rare astronomical spectacle as soon as possible after sunset.”
“Those who prefer to wait and see Jupiter and Saturn this close together and higher in the night sky will have to stick around until March 15, 2080.”
“After that, the couple won’t make such an appearance until after 2400.”
_____
This article is based on text provided by the National Aeronautics and Space Administration and Rice University.
[ad_2]
Source link