[ti:Jupiter, Saturn Come Together in Night Sky]
[al:Science & Technology]
[ar:VOA]
[dt:2020-12-22]
[by:www.voase.cn]
[00:00.00]The planets Jupiter and Saturn have been moving closer and closer to each other in the night sky. 
[00:09.91]In fact, on December 21, they appear closer together than they have in hundreds of years.
[00:18.56]When two astronomical bodies appear close in the sky, as seen from Earth, it is called a conjunction. 
[00:29.19]Conjunctions can happen with any two bodies, such as planets, moons, stars and asteroids.
[00:37.94]When Jupiter and Saturn come together, it is called a "Great Conjunction."
[00:44.07]Astronomers say these events between the two largest planets in our solar system are not especially rare. 
[00:53.88]Jupiter passes its neighbor Saturn once every 20 years as they circle around the sun.
[01:02.67]But this conjunction is especially close: From Earth, the two planets will look to be just one-tenth of a degree apart. 
[01:15.94]That is about the distance of one-fifth of a full moon.
[01:21.44]If weather permits, they should be easy to see just after sundown.
[01:28.29]This just-in-time-for-Christmas sight promises to be one of the greatest of Great Conjunctions.
[01:37.80]David Weintraub is an astronomy professor at Vanderbilt University. 
[01:44.58]He told The Associated Press that a close conjunction that happens in our nighttime sky is very rare.
[01:55.65]"I think it's fair to say" that such an event usually may happen "just once in any one person's lifetime," he said. 
[02:06.52]"And I think 'once in my lifetime' is a pretty good test" of whether something should be considered rare or special.
[02:16.35]The Jupiter-Saturn conjunction has not been this close since July 1623.
[02:24.66]But, back then, the positioning was almost impossible to see because of its closeness to the sun.
[02:34.55]What makes this modern "Great Conjunction" special is it is happening at nighttime.
[02:42.58]The last time that happened was almost 800 years go.
[02:49.63]The year was March 1226. 
[02:54.01]Around that time, warrior-ruler Genghis Khan was conquering Asia.
[03:01.82]Saturn and Jupiter have been getting closer in the south-southwest sky for weeks.
[03:09.66]Jupiter, which is bigger and closer to Earth, is much brighter.
[03:15.25]"I love watching them come closer and closer to each other," said Nahum Arav in an email.
[03:24.30]He is an astronomer at Virginia Tech University. 
[03:29.02]He said he loves the fact that he will see with his own eyes from his own home.
[03:37.49]The two planets might look like one body if viewed with eyes alone. 
[03:44.91]If sky watchers use binoculars they should be able to see the planets as separate.
[03:51.99]Saturn will be the smaller, less-bright body at Jupiter's upper right.
[03:58.99]Even though they appear close, more than 730 million kilometers of space lies between them.
[04:08.27]Observers using telescopes will not only capture Jupiter and Saturn in the same field of view, but also some of their brightest moons.
[04:20.08]Their next close pairing will happen March 15, 2080.
[04:27.31]I'm Alice Bryant.