On Monday, ‘Christmas Star’ appears in sky for first time in 800 years: how to see great conjunction if weath - OregonLive

A phenomenon not seen for nearly 800 years will light up the sky next week.

Two of the largest planets in the solar system will come together in “a great conjunction” right in time for Christmas, NASA reported. It is also the same day as the winter solstice.

“What has become known popularly as the ‘Christmas Star’ is an especially vibrant planetary conjunction easily visible in the evening sky over the next two weeks as the bright planets Jupiter and Saturn come together, culminating on the night of Dec. 21,” NASA said on its website.

On Monday, Jupiter and Saturn will inch closer and closer to each other to be in conjunction, according to Space.com. The two planets rarely come together like other bright planets do.

Jim Todd, director of space science education at OMSI, said those in the Portland area will want to head outside just after sunset at 4:30 p.m., when Jupiter and Saturn will be low in the sky. The planets will set below the horizon quickly, Todd said, so a good view of the southwestern horizon is necessary, and people will need to look skyward in time to catch it.

The weather in Portland doesn’t look to be favorable with a 70-80% chance of rain and a forecast of mostly cloudy Monday.

NASA says, for those who would like to see this phenomenon for themselves, here’s what to do:

• Find a spot with an unobstructed view of the sky, such as a field or park. Jupiter and Saturn are bright, so they can be seen even from most cities.
• An hour after sunset, look to the southwestern sky. Jupiter will look like a bright star and be easily visible. Saturn will be slightly fainter and will appear slightly above and to the left of Jupiter until December 21, when Jupiter will overtake it and they will reverse positions in the sky.
• The planets can be seen with the unaided eye, but if you have binoculars or a small telescope, you may be able to see Jupiter’s four large moons orbiting the giant planet.

The conjunction of the two planets happens about every 20 years, but they’re not always the same. Monday will be the closest Jupiter-Saturn pairing since July 1623, when the two planets appeared a little nearer. This conjunction was almost impossible to see, however, because of its closeness to the sun.

Considerably closer and in plain view was the March 1226 conjunction of the two planets — when Genghis Khan was conquering Asia. Monday’s conjunction will be the closest pairing that is visible since way back then.

Saturn will be the smaller, fainter blob at much brighter Jupiter’s upper right. Despite appearances, Jupiter and Saturn will actually be more than 450 million miles (730 million kilometers) apart. Earth, meanwhile, will be 550 million miles (890 million kilometers) from Jupiter.

“On the 21st, they will appear so close that a pinkie finger at arm’s length will easily cover both planets in the sky,” NASA said. “The planets will be easy to see with the unaided eye by looking toward the southwest just after sunset.”

The best way to catch a glimpse of the rare phenomenon is to look about one hour after sunset, according to NASA. The planets are visible with the naked eye.

“Jupiter will look like a bright star and be easily visible,” NASA said. “Saturn will be slightly fainter and will appear slightly above and to the left of Jupiter until Dec. 21, when Jupiter will overtake it and they will reverse positions in the sky.”

The next time they will get this close together in our sky won’t be for another 60 years, so this is going to be a once-in-a-lifetime event for many people. In fact, the last time they got this close together was in the year 1623, but it was really difficult, if not impossible, to see them then because they appeared much closer to the Sun and set soon after it. Go back another 400 years to 1226 and this would have been the last time that we would have had a good view of this type of conjunction.

What advice would you give to people who want to see the great conjunction?

If you have a pair of binoculars, you’ll easily be able to spot both planets. In even a small telescope, you’d see both planets at the same time in the same field of view, which is really unheard of. That’s what makes this conjunction so rare.

If weather permits at Dyer Observatory, there will be a live stream of the conjunction from one of the observatory’s telescopes.

Toss in the winter solstice in the Northern Hemisphere, the longest night of the year — and the summer solstice in the Southern Hemisphere — and this just-in-time-for-Christmas spectacle promises to be one of the greatest of Great Conjunctions.

“What is most rare is a close conjunction that occurs in our nighttime sky,” said Vanderbilt University’s David Weintraub, an astronomy professor. “I think it’s fair to say that such an event typically may occur just once in any one person’s lifetime, and I think ‘once in my lifetime’ is a pretty good test of whether something merits being labeled as rare or special.”

Their next super-close pairing: March 15, 2080.

-- Kansas City Star, The Associated Press, The Conversation

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