APOD: Great Conjunction: Saturn and... (2020 Dec 15)

[APOD Robot]

Great Conjunction: Saturn and Jupiter Converge

Explanation: It's happening. Saturn and Jupiter are moving closer and will soon appear in almost exactly the same direction. Coincidentally, on the night of the December solstice -- the longest night of the year in the north and the longest day in the south -- the long-awaited Great Conjunction will occur. Then, about six days from now, Saturn and Jupiter will be right next to each other -- as they are every 20 years. But this juxtaposition is not just any Great Conjunction -- it will be the closest since 1623 because the two planetary giants will pass only 1/10th of a degree from each other -- well less than the apparent diameter of a full moon. In the next few days a crescent moon will also pass a few degrees away from the converging planets and give a preliminary opportunity for iconic photos. The featured illustration shows the approach of Saturn and Jupiter during November and December over the French Alps.

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[Case]

A tough one, so close to the setting Sun, so close to the horizon. On the other hand, this one is not about planetary surface details.

[Iksarfighter]

Are they visible on the morning or on the evening please ?

[seadogzz]

When will be the best time to view in southern UK about Dec 19-22?
Will it be visible at/before sunrise, or only in the evening?
Regards

[Sa Ji Tario]

In 2020 only at sunset

[Sa Ji Tario]

In the last 20 years, the solstice has occurred on December 21 13 times and on December 22 7 times in hours ranging from sunrise to 11 p.m.

[orin stepanek]

Nicely shown! 🥰 ;

[seadogzz]

Thanks for your help

[E Fish]

I wish some in the media (social and otherwise) wouldn't talk about this as if Saturn and Jupiter in conjunction is somehow going to be significantly brighter, though. I've seen some things implying it's going to be like a supernova. It's a really cool event but when it gets built up so much, the reality becomes a disappointment. That happens whenever Mars is at perigee. Invariably, there's something that goes around saying that Mars will be as big as the full Moon.

But the image is very nice to show what it will look like. Given my luck, it'll probably snowing in my area on that day.

[Chris Peterson]

A tough one, so close to the setting Sun, so close to the horizon. On the other hand, this one is not about planetary surface details.

I plan on shooting images around local noon on the 21st, which for me will put them in the southeastern sky just past their point of being closest (which is slightly before they rise for me).

Both of these objects are plenty bright to be telescopic objects in full daylight. I'll go for wider field astro-landscape type images just after sunset.

[DL MARTIN]

GREAT STUFF. Hope the media picks this illustration up globally. Thank you.

[Chris Peterson]

I wish some in the media (social and otherwise) wouldn't talk about this as if Saturn and Jupiter in conjunction is somehow going to be significantly brighter, though. I've seen some things implying it's going to be like a supernova. It's a really cool event but when it gets built up so much, the reality becomes a disappointment. That happens whenever Mars is at perigee. Invariably, there's something that goes around saying that Mars will be as big as the full Moon.

But the image is very nice to show what it will look like. Given my luck, it'll probably snowing in my area on that day. :)

Quite the opposite, in fact. This would be far more spectacular if the two planets were near opposition. In fact, they are nearing conjunction with the Sun, meaning they are close to being as small and dim as they ever get.

[florid_snow]

I plan on shooting images around local noon on the 21st, which for me will put them in the southeastern sky just past their point of being closest (which is slightly before they rise for me).

Both of these objects are plenty bright to be telescopic objects in full daylight. I'll go for wider field astro-landscape type images just after sunset.

Excellent point, my plan was to do basically the same but wait until they hit my local meridian. Are you thinking the trade-off of looking through more atmosphere, but at a less turbulent time might be worth it? Thanks for the tip!

[Chris Peterson]

I plan on shooting images around local noon on the 21st, which for me will put them in the southeastern sky just past their point of being closest (which is slightly before they rise for me).

Both of these objects are plenty bright to be telescopic objects in full daylight. I'll go for wider field astro-landscape type images just after sunset.

Excellent point, my plan was to do basically the same but wait until they hit my local meridian. Are you thinking the trade-off of looking through more atmosphere, but at a less turbulent time might be worth it? Thanks for the tip!

The ecliptic is so low that the difference in altitude isn't very much from mid-morning to mid-afternoon. My main reasoning is that my observatory wall is already partly blocking the telescope, but I can see a bit lower towards the corners- SE and SW. I'll also try imaging later in the day, and the forecast is for clear skies, but you never know. so if I have a chance in the morning, I"m not going to overlook it!

[bls0326]

About an hour after sunset on Dec. 13th, I looked out my front door (facing south) and there they were! Quite obvious. Mostly clouds since then, but hoping for a view as they get closer together.

[bystander]

Jupiter & Saturn Have Historic Dusk Encounter
Sky & Telescope | 2020 Dec 15

This illustration shows the view facing southwest at dusk on December 21st. Jupiter should be an easy find, but Saturn may require careful scrutiny. Credit: Sky & Telescope / Gregg Dinderman

---

[orin stepanek]

Jupiter & Saturn Have Historic Dusk Encounter
Sky & Telescope | 2020 Dec 15

This illustration shows the view facing southwest at dusk on December 21st. Jupiter should be an easy find, but Saturn may require careful scrutiny. Credit: Sky & Telescope / Gregg Dinderman

---

Thanks; bystander, nice rendering!

[Chris Peterson]

Quick and dirty- rapid setup of my little refractor. It was 12°F and I wasn't really dressed for it. Just after sunset on 15 Dec, bad seeing. But the first time I've ever had the pair in the same telescopic field.
_

[alter-ego]

I plan on shooting images around local noon on the 21st, which for me will put them in the southeastern sky just past their point of being closest (which is slightly before they rise for me).

Although not necessarily a plan changer, the closest separation occurs at positive altitudes for you. I plotted JPL Horizons results.

• The minimum separation actually occurs at ~18:30 12/21 UTC
  The plot compares the conjunction details, timing and separation, for the geocentric case plus topocentric circumstances: Colorado Springs, with and without refraction. As it should be, topocentric (without refraction) and geocentric cases agree very well. The addition of refraction (topocentric) introduces a relatively significant reduction in angular separation when the planets rise due to the refractive index gradient at low altitudes.

Of course, this is more an interesting detail than a practical one, but barring any observatory-view limitations and you should be able to observe the planets at minimum separation (~20°at CS, ~19° at Guffy). I don't find the refraction affect valuable here due to it's dynamic and unpredictable nature.

Edit: Discovered calculation error for topocentric circumstances. Corrected post accordingly.

[JohnD]

People ask, Is this the Christmas Star?
I read - I don't KNOW this sort of thing! - that planets' orbital mechnaics being completely calculable, there WAS such a Great Conjunction, in 7BC.
But there was another, between Jupiter and Venus, in 2BC. That would have been brighter than this one and must have drawn the attention of Magi, in large numbers! In terms of Biblical dating, an error of 2 years is surely insignificant, so this wasn't the Christmas Star, but it was one very like it!

[neufer]

People ask, Is this the Christmas Star?

I read - I don't KNOW this sort of thing! - that planets' orbital mechnaics being completely calculable, there WAS such a Great Conjunction, in 7BC.
But there was another, between Jupiter and Venus, in 2BC. That would have been brighter than this one and must have drawn the attention of Magi, in large numbers! In terms of Biblical dating, an error of 2 years is surely insignificant, so this wasn't the Christmas Star, but it was one very like it!

Click to play embedded YouTube video.

<<In 1614, German astronomer Johannes Kepler determined that a series of three conjunctions of the planets Jupiter and Saturn occurred in the year 7 BC. He argued (incorrectly) that a planetary conjunction could create a nova, which he linked to the Star of Bethlehem. Modern calculations show that there was a gap of nearly a degree (approximately twice a diameter of the moon) between the planets, so these conjunctions were not visually impressive. An ancient almanac has been found in Babylon which covers the events of this period, but does not indicate that the conjunctions were of any special interest. In the 20th century, Professor Karlis Kaufmanis, an astronomer, argued that this was an astronomical event where Jupiter and Saturn were in a triple conjunction in the constellation Pisces. Archaeologist and Assyriologist Simo Parpola has also suggested this explanation.

In 6 BC, there were conjunctions/occultations (eclipses) of Jupiter by the Moon in Aries. "Jupiter was the regal 'star' that conferred kingships – a power that was amplified when Jupiter was in close conjunctions with the Moon. The second occultation on April 17 coincided precisely when Jupiter was 'in the east', a condition mentioned twice in the biblical account about the Star of Bethlehem."

In 3–2 BC, there was a series of seven conjunctions, including three between Jupiter and Regulus and a strikingly close conjunction between Jupiter and Venus near Regulus on June 17, 2 BC. "The fusion of two planets would have been a rare and awe-inspiring event", according to Roger Sinnott. Another Venus–Jupiter conjunction occurred earlier in August, 3 BC. These events however occurred after the generally accepted date of 4 BC for the death of Herod. Since the conjunction would have been seen in the west at sunset it could not have led the magi south from Jerusalem to Bethlehem.>>

[Chris Peterson]

People ask, Is this the Christmas Star?
I read - I don't KNOW this sort of thing! - that planets' orbital mechnaics being completely calculable, there WAS such a Great Conjunction, in 7BC.
But there was another, between Jupiter and Venus, in 2BC. That would have been brighter than this one and must have drawn the attention of Magi, in large numbers! In terms of Biblical dating, an error of 2 years is surely insignificant, so this wasn't the Christmas Star, but it was one very like it!

The most compelling evidence is that the myth stems from astrological interpretations, not anything that was actually visible in the sky. (Remember that the Nativity stories weren't constructed until long after the events they purport to describe.)

[JohnD]

The Magi went to Jerusalem and King Herod, "Saying, Where is he that is born King of the Jews? for we have seen his star in the east"
But the same verse in Matthew says "there came wise men from the east to Jerusalem". If from a point East of Jerusalem they had seen it in their East, they would have gone East and Jesus would have been born in India!
So the Bible is already confused!
But the great Pre-Roman civilisation on the Tigris and Euphrates rivers, East of Jerusalem had priests magicians and astrologers, who WOULD have seen the Great Conjunction of their time in the West, as we do, and followed it towards Isreal.

Massive movements like Christianity aquire much legend and folklore, but they do have sparks of truth in their origins.
For me, an atheist, I feel that there WAS someone called Jesus, born under a portenteous star, who grew up to be a philosopher and religious leader, who came to an awful end. His teaching on the way to conduct one's life is exemplary, such as respecting the family and giving charity by gifts (thoroughly good Jewish teaching too, of course!) so why not celebrate what we think was his birthday in that way?
John

[Chris Peterson]

The Magi went to Jerusalem and King Herod, "Saying, Where is he that is born King of the Jews? for we have seen his star in the east"
But the same verse in Matthew says "there came wise men from the east to Jerusalem". If from a point East of Jerusalem they had seen it in their East, they would have gone East and Jesus would have been born in India!
So the Bible is already confused!
But the great Pre-Roman civilisation on the Tigris and Euphrates rivers, East of Jerusalem had priests magicians and astrologers, who WOULD have seen the Great Conjunction of their time in the West, as we do, and followed it towards Isreal.

Massive movements like Christianity aquire much legend and folklore, but they do have sparks of truth in their origins.
For me, an atheist, I feel that there WAS someone called Jesus, born under a portenteous star, who grew up to be a philosopher and religious leader, who came to an awful end. His teaching on the way to conduct one's life is exemplary, such as respecting the family and giving charity by gifts (thoroughly good Jewish teaching too, of course!) so why not celebrate what we think was his birthday in that way?
John

"Portentous star" sounds a lot more astrological than astronomical.

[Chris Peterson]

I plan on shooting images around local noon on the 21st, which for me will put them in the southeastern sky just past their point of being closest (which is slightly before they rise for me).

Although not necessarily a plan changer, the closest separation occurs at positive altitudes for you. But there's an interesting twist for when the closest separation occurs. It involves topocentric circumstances.

That's interesting.

In reality, I'll probably be shooting images all day, and with different equipment. We'll see what I get.