Catch an Awe-Inspiring Great Conjunction of Jupiter and Saturn on December 21st

The solar system’s two massive gas giant planets pair up at dusk on December 21st, with a rare conjunction of Jupiter and Saturn.

A once-in-a-lifetime view is about to grace the dusk sky worldwide, closing out 2020 with one of the best astronomical events of the year.

Continue reading “Catch an Awe-Inspiring Great Conjunction of Jupiter and Saturn on December 21st”

Is This Month’s Jupiter-Venus Pair Really a Star of Bethlehem Stand In?

Image credit and copyright: Clapiotte Astro

Eclipse tetrads of doom. Mars, now bigger than the Full Moon each August. The killer asteroid of the month that isn’t. Amazing Moons of all stripes, Super, Blood, Black and Blue…

Image credit and copyright: @TaviGrainer(ck)
Venus, Mars, Jupiter and the Moon from October 9th. Image credit and copyright: @TaviGreiner

The internet never lets reality get in the way of a good meme, that’s for sure. Here’s another one we’ve caught in the wild this past summer, one that now appears to be looking for a tenuous referent to grab onto again next week.

You can’t miss Jupiter homing in on Venus this month, for a close 61.5’ pass on the morning on Oct 25th. -1.4 magnitude Jupiter shows a 33” disk on Sunday’s pass, versus -4 magnitude Venus’ 24” disk.

Oct 26 Stellarium
Looking east on the morning of October 26th. Credit: Stellarium

We also had a close pass on July 1st, which prompted calls of ‘the closest passage of Venus and Jupiter for the century/millennia/ever!’ (spoiler alert: it wasn’t) Many also extended this to ‘A Star of Bethlehem convergence’ which, again, set the web a-twittering.

Will the two brightest planets in the sky soon converge every October, in the minds of Internet hopefuls?

This idea seems to come around every close pass of Jupiter and Venus as of late, and may culminate next year, when an extra close 4’ pass occurs on August 27th, 2016. But the truth is, close passes of Venus and Jupiter are fairly common, occurring 1-2 times a year. Venus never strays more than 47 degrees from the Sun, and Jupiter moves roughly one astronomical constellation eastward every Earth year.

Much of the discussion in astrological circles stems from the grouping of Jupiter, Venus and the bright star Regulus this month. Yes, this bears a resemblance to a grouping of the same seen in dawn skies on August 12th, 2 BCE. This was part of a series of Jupiter-Venus conjunctions that also occurred on May 24th, 3 BCE and June 17th, 1 BCE. The 2 BCE event was located in the constellation Leo the Lion, and Regulus rules the sign of kings in the minds of many…

Looking eastward on the morning of August 12th, 2 BCE. Credit: Stellarium

But even triple groupings are far from uncommon over long time scales. Pairings of Jupiter, Venus in any given zodiac constellation come back around every 11-12 years. Many great astronomical minds over the centuries have gone broke trying to link ‘The Star’ seen by the Magi to the latest astronomical object in vogue, from conjunctions, to comets, to supernovae and more. If there’s any astronomical basis to the allegorical tale, we’ll probably never truly know.

Starry Night
The October 25th pass of Venus vs Jupiter. Created using Starry Night Education software.

Aaron Adair, the author of The Star of Bethlehem: A Skeptical View has this to say to Universe Today:
“The 3/2 BCE conjunctions don’t fit the time of Jesus’ birth. There is also no evidence that these sorts of conjunctions were considered all that good; I even found evidence that they were bad news for a king, especially if Jupiter was circling around Regulus. And of course, none of this even comes close to doing the things the Star of Bethlehem was claimed to have done. 
So, we have a not terribly rare situation in the sky that conforms to something that doesn’t really fit the Gospel story in a time frame that doesn’t fit the Jesus chronology which doesn’t really have anything all that auspicious about that to ancient observers.” 

The dance of the planets also gives us a brief opening teaser on Saturday morning, as Mars  passes just 0.38 degrees NNE of Jupiter on Oct 17th looking like a fifth pseudo-moon.

Finally, the crescent Moon joins the scene once again on November 7th, passing 1.9 degrees SSW of Jupiter and 1.2 SSW of Venus, a great time to attempt to spy both in the daytime using the crescent Moon as a guide. And keep an eye on Venus, as the next passage of the crescent Moon on December 7th features a close grouping with binocular Comet C/2013 US10 Catalina as well.

How close can the two planets get?

Stick around ‘til November 22nd 2065, and you can watch Venus actually transit the face of Jupiter:

Though rare, such an occlusion involving the two brightest planets happens every other century or so… we ran a brief simulation, and uncovered 11 such events over the next three millennia:

Credit: Dave Dickinson
Credit: Dave Dickinson

Bruce McCurdy of the Royal Canadian Astronomical Society posed a further challenge: how often does Venus fully occult Jupiter? We ran a simulation covering 9000 BC to 9000 AD, and found no such occurrence, though the July 14th, 4517 AD meeting of Jupiter and Venus is close.

Let’s see, I’ll be on my 3rd cyborg body, in the post- Robot Apocalypse by then…

This sort of total occlusion of Jupiter by Venus turns out to be rarer than any biblical conjunction. Why?

Well, for one thing, Venus is generally smaller in apparent size than Jupiter. When Jupiter is near Venus, it’s also near the Sun and in the 30-35” size range. Venus only breaks 30” in size for about 20% of its 584 synodic period. But we suspect a larger cycle may be in play, keeping the occurrence of a large Venus meeting and covering a shrunken Jove in our current epoch.

A Moon, a star, three planets and... a space station? A close pass of Tiangong-1 (arrowed) near this month's grouping. Image credit: Dave Dickinson
A Moon, a star, three planets and… a space station? A close pass of Tiangong-1 (arrowed) near this month’s grouping. Image credit: Dave Dickinson

Astronomy makes us ponder the weirdness of our skies gracing our backyard over stupendously long time scales. Whatever your take on the tale and the modern hype, be sure to get out and enjoy the real show on Sunday morning October 25th, as the brightest of planets make for a brilliant pairing.