APOD: Planetary Alignment over Italy (2021 Dec 19)

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APOD: Planetary Alignment over Italy (2021 Dec 19)

Post by APOD Robot » Sun Dec 19, 2021 5:05 am

Image Planetary Alignment over Italy

Explanation: It is not a coincidence that planets line up. That's because all of the planets orbit the Sun in (nearly) a single sheet called the plane of the ecliptic. When viewed from inside that plane -- as Earth dwellers are likely to do -- the planets all appear confined to a single band. It is a coincidence, though, when three of the brightest planets all appear in nearly the same direction. Such a coincidence was captured earlier this month. Featured above (right to left), Venus, Saturn, and Jupiter were all imaged together in a line just after sunset, from the San Fermo Hills, Bergamo, Italy. Joining the alignment are Earth's Moon, and the position of the more distant Uranus. Bands of clouds streak across the sky toward the setting Sun. As Comet Leonard fades, this planetary alignment -- absent the Moon -- should persist for the rest of the month.

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Re: APOD: Planetary Alignment over Italy (2021 Dec 19)

Post by heehaw » Sun Dec 19, 2021 11:15 am

Hey, just wait til the year 2492: https://henry.pha.jhu.edu/2492.png

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Re: APOD: Planetary Alignment over Italy (2021 Dec 19)

Post by rj rl » Sun Dec 19, 2021 12:39 pm

Looks like noctilucent clouds also made an appearance. Isn't Italy a bit too southern to see them? They're also towards the south :| :?:

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Re: APOD: Planetary Alignment over Italy (2021 Dec 19)

Post by Sa Ji Tario » Sun Dec 19, 2021 3:17 pm

I estimate that it was in the 60s of the last century that something similar happened and led to the launch of the two Voyagers with the results that are known, the new discoveries led to new explorations and today there are innumerable probes roaming the cosmic neighborhood in search news .-
I understand that on average every 160 years planetary alignments will occur, although some will be in opposition, this achieved a diffusion of the science of Astronomy as it was never known

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Re: APOD: Planetary Alignment over Italy (2021 Dec 19)

Post by Chris Peterson » Sun Dec 19, 2021 3:22 pm

Not apparent in this image, but present all the same... Neptune lies on a line almost exactly between the Moon and Jupiter, and Pluto is in conjunction with Venus, lying just a half a degree below it. (Mercury is just below the horizon, and could theoretically have been captured had the image been made a few minutes earlier... although that would have been so shortly after sunset that the sky might have been too bright to see either it or Uranus, and maybe even Saturn. Jupiter and Venus can both be seen while the Sun is still above the horizon, if you look carefully.)
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Re: APOD: Planetary Alignment over Italy (2021 Dec 19)

Post by orin stepanek » Sun Dec 19, 2021 3:32 pm

PlanetsAligned_Finazzi_3757.jpg
I had trouble spotting Saturn; and Uranus I couldn't spot!
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Cute critter; even has a telephone dial nose! :mrgreen:
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Aw! Good doggie giving tired kitty a lift! :lol2:
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Re: APOD: Planetary Alignment over Italy (2021 Dec 19)

Post by johnnydeep » Sun Dec 19, 2021 10:13 pm

heehaw wrote: Sun Dec 19, 2021 11:15 am Hey, just wait til the year 2492: https://henry.pha.jhu.edu/2492.png
Wait - why don't the planets shown there appear nearly in a straight line?

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Re: APOD: Planetary Alignment over Italy (2021 Dec 19)

Post by neufer » Mon Dec 20, 2021 4:57 am

johnnydeep wrote: Sun Dec 19, 2021 10:13 pm
heehaw wrote: Sun Dec 19, 2021 11:15 am
Hey, just wait til the year 2492: https://henry.pha.jhu.edu/2492.png
Wait - why don't the planets shown there appear nearly in a straight line?
  • All (seven planets?) in the same 180° wide path of the sky :?:

    This is not my understanding of the true significance of May 6, 2492:
https://en.wikipedia.org/wiki/List_of_future_astronomical_events wrote:
<<May 6, 2492 : Belgian astronomer Jean Meeus asserts that the orbits of all eight planets and Pluto will be within the same 90° arc (i.e., heliocentric longitude) of the Solar System.

The last time this is believed to have occurred was on February 1, 949.
>>
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Re: APOD: Planetary Alignment over Italy (2021 Dec 19)

Post by johnnydeep » Mon Dec 20, 2021 2:04 pm

neufer wrote: Mon Dec 20, 2021 4:57 am
johnnydeep wrote: Sun Dec 19, 2021 10:13 pm
heehaw wrote: Sun Dec 19, 2021 11:15 am
Hey, just wait til the year 2492: https://henry.pha.jhu.edu/2492.png
Wait - why don't the planets shown there appear nearly in a straight line?
  • All (seven planets?) in the same 180° wide path of the sky :?:

    This is not my understanding of the true significance of May 6, 2492:
https://en.wikipedia.org/wiki/List_of_future_astronomical_events wrote:
<<May 6, 2492 : Belgian astronomer Jean Meeus asserts that the orbits of all eight planets and Pluto will be within the same 90° arc (i.e., heliocentric longitude) of the Solar System.

The last time this is believed to have occurred was on February 1, 949.
>>
Ok, but you didn't address my "not in the same line" question. So, I looked up the orbital inclinations of the planets and only Pluto (17 degrees) and Mercury (7 degrees) are the odd men out, with the other planets all under 3.5 degrees orbital plane inclination. So, I guess that jives with the image.

EDIT: I used this chart:
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Re: APOD: Planetary Alignment over Italy (2021 Dec 19)

Post by Chris Peterson » Mon Dec 20, 2021 2:45 pm

johnnydeep wrote: Sun Dec 19, 2021 10:13 pm
heehaw wrote: Sun Dec 19, 2021 11:15 am Hey, just wait til the year 2492: https://henry.pha.jhu.edu/2492.png
Wait - why don't the planets shown there appear nearly in a straight line?

They look pretty darn straight to me!
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Re: APOD: Planetary Alignment over Italy (2021 Dec 19)

Post by neufer » Mon Dec 20, 2021 3:32 pm

johnnydeep wrote: Mon Dec 20, 2021 2:04 pm
neufer wrote: Mon Dec 20, 2021 4:57 am
johnnydeep wrote: Sun Dec 19, 2021 10:13 pm

Wait - why don't the planets shown there appear nearly in a straight line?
  • All (seven planets?) in the same 180° wide path of the sky :?:

    This is not my understanding of the true significance of May 6, 2492:
https://en.wikipedia.org/wiki/List_of_future_astronomical_events wrote:
<<May 6, 2492 : Belgian astronomer Jean Meeus asserts that the orbits of all eight planets and Pluto will be within the same 90° arc (i.e., heliocentric longitude) of the Solar System.

The last time this is believed to have occurred was on February 1, 949.
>>
Ok, but you didn't address my "not in the same line" question. So, I looked up the orbital inclinations of the planets and only Pluto (17 degrees) and Mercury (7 degrees) are the odd men out, with the other planets all under 3.5 degrees orbital plane inclination. So, I guess that jives with the image.
Pluto isn't even shown in the https://henry.pha.jhu.edu/2492.png image ...
while Mars (1.9°) & Neptune (1.8°) are the most obvious planets "not in the same line."

I went to: http://www.faustweb.net/solaris/ and put
in the dates: 6-5-2492 & 1-2-949 which shows:
  • 1) agreement with the https://henry.pha.jhu.edu/2492.png image and
    2) agreement with all eight planets being within the same 90° arc (i.e., heliocentric longitude) of the Solar System.
However,
  • All (seven planets?) are NOT in the same 180° wide path of the sky on February 1, 949.

    This type of alignment is much easier when ONLY the seven shown planets are within the same 90° arc
    (i.e., heliocentric longitude) of the Solar System while a (non-aligned) Earth observes them from afar.

    (6-5-2492 & 1-2-949 (eight planet) alignments are rarer birds... especially if Pluto is included :!: )
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Re: APOD: Planetary Alignment over Italy (2021 Dec 19)

Post by johnnydeep » Mon Dec 20, 2021 4:34 pm

Neufer wrote "while Mars (1.9°) & Neptune (1.8°) are the most obvious planets "not in the same line."

Yeah, I overlooked that Pluto isn't shown, but from a purely line-fitting POV, depending on the line you choose, it looks like either Mercury and Jupiter are off it, or maybe Mercury and Venus. How are you picking Mars and Neptune?
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Re: APOD: Planetary Alignment over Italy (2021 Dec 19)

Post by neufer » Mon Dec 20, 2021 4:50 pm

johnnydeep wrote: Mon Dec 20, 2021 4:34 pm
Neufer wrote "while Mars (1.9°) & Neptune (1.8°) are the most obvious planets "not in the same line."

Yeah, I overlooked that Pluto isn't shown, but from a purely line-fitting POV, depending on the line you choose, it looks like either Mercury and Jupiter are off it, or maybe Mercury and Venus. How are you picking Mars and Neptune?
They are adjacent to each other and, hence, most obviously out of ( great circle) alignment.
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Re: APOD: Planetary Alignment over Italy (2021 Dec 19)

Post by alter-ego » Wed Dec 22, 2021 5:15 am

neufer wrote: Mon Dec 20, 2021 4:50 pm
johnnydeep wrote: Mon Dec 20, 2021 4:34 pm
Neufer wrote "while Mars (1.9°) & Neptune (1.8°) are the most obvious planets "not in the same line."

Yeah, I overlooked that Pluto isn't shown, but from a purely line-fitting POV, depending on the line you choose, it looks like either Mercury and Jupiter are off it, or maybe Mercury and Venus. How are you picking Mars and Neptune?
They are adjacent to each other and, hence, most obviously out of ( great circle) alignment.
The Stellarium views show the two planetary configurations discussed. I'm showing only the planets, sun and moon with the best eyeball-fit for a great circle. Also, atmosphere and ground removed. For both cases, the "line" is a great-circle arc, and the planets line up quite well to this arc. Relatively speaking, Pluto is the most off. With regard to planetary alignment, image creation (image projection to the sensor plane and FoV) matters. For the Stellarium simulations, finding the best alignment sweet spot was straight :!: forward.
 
Today's APOD - Surprise! Neptune is also present and fits well on the line. It's just not visible. It is 2+ magnitudes fainter, and the clouds don't help. It doesn't matter here, but I did set the view from in or around Italy on Dec 12. (Note, I did not weight Ceres in the fit.)
 
stellarium-008.png
 
May 6, 2492 - Here too, the planets align well, except for Pluto which is really off by about 12°.
 
stellarium-012.jpg
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Re: APOD: Planetary Alignment over Italy (2021 Dec 19)

Post by Ann » Wed Dec 22, 2021 5:31 am

alter-ego wrote: Wed Dec 22, 2021 5:15 am
neufer wrote: Mon Dec 20, 2021 4:50 pm
johnnydeep wrote: Mon Dec 20, 2021 4:34 pm
Neufer wrote "while Mars (1.9°) & Neptune (1.8°) are the most obvious planets "not in the same line."

Yeah, I overlooked that Pluto isn't shown, but from a purely line-fitting POV, depending on the line you choose, it looks like either Mercury and Jupiter are off it, or maybe Mercury and Venus. How are you picking Mars and Neptune?
They are adjacent to each other and, hence, most obviously out of ( great circle) alignment.
The Stellarium views show the two planetary configurations discussed. I'm showing only the planets, sun and moon with the best eyeball-fit for a great circle. Also, atmosphere and ground removed. For both cases, the "line" is a great-circle arc, and the planets line up quite well to this arc. Relatively speaking, Pluto is the most off. With regard to planetary alignment, image creation (image projection to the sensor plane and FoV) matters. For the Stellarium simulations, finding the best alignment sweet spot was straight :!: forward.
 
Today's APOD - Surprise! Neptune is also present and fits well on the line. It's just not visible. It is 2+ magnitudes fainter, and the clouds don't help. It doesn't matter here, but I did set the view from in or around Italy on Dec 12. (Note, I did not weight Ceres in the fit.)
   
May 6, 2492 - Here too, the planets align well, except for Pluto which is really off by about 12°.
 
Impressive, alter-ego! Does that mean that today's alignment is extremely rare?

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Re: APOD: Planetary Alignment over Italy (2021 Dec 19)

Post by alter-ego » Wed Dec 22, 2021 6:21 am

Ann wrote: Wed Dec 22, 2021 5:31 am ...

Impressive, alter-ego! Does that mean that today's alignment is extremely rare?

Ann
Well, thanks, Ann :ssmile:
Yes! Extremely rare!!

Below, Pluto is designated by the red cursor (also surrounding Venus!). Yes, at 13:00UT, Pluto reaches minimum separation from Venus < 4 arc minutes 8.5 hours later than the simulation time.!
This simulation also shows mars on the other side of the sun, but none the less, the 7 planets + Pluto are lined up within 180°.
Mars wasn't visible at the same time since it's on the other side of the sun, and Pluto extremely close to Venus.
 
stellarium-014.png

Edit: I just saw I missed Chris' earlier post (twice!!) on both Neptune and Pluto. I couldn't believe that these hadn't come up! Indeed, I found they had. No matter, seeing / verifying the line-ups is still interesting. (I still can't believe I missed that :lol2: )
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Re: APOD: Planetary Alignment over Italy (2021 Dec 19)

Post by johnnydeep » Wed Dec 22, 2021 12:57 pm

Alright, alter-ego's exacting work above notwithstanding, why again don't the planets appear to be in a straight line in the image neufer posted showing the alignment in year 2492. Is it merely an artifact of the perhaps panoramic view?

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Re: APOD: Planetary Alignment over Italy (2021 Dec 19)

Post by Chris Peterson » Wed Dec 22, 2021 1:40 pm

johnnydeep wrote: Wed Dec 22, 2021 12:57 pm Alright, alter-ego's exacting work above notwithstanding, why again don't the planets appear to be in a straight line in the image neufer posted showing the alignment in year 2492. Is it merely an artifact of the perhaps panoramic view?

The planets are not in a line. They lie on the same plane (or nearly so). Similarly, the horizon isn't a line, but represents a plane. And those two planes are not the same- they are tilted with respect to each other. Project the image so the planets are in a line, and the horizon will be curved (as we see in the APOD image). Project the image so the horizon is a line, and the ecliptic will be curved (as we see in the simulation). You can't have both.
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Re: APOD: Planetary Alignment over Italy (2021 Dec 19)

Post by neufer » Wed Dec 22, 2021 1:40 pm

johnnydeep wrote: Wed Dec 22, 2021 12:57 pm
Alright, alter-ego's exacting work above notwithstanding, why again don't the planets appear to be in a straight line in the image neufer posted showing the alignment in year 2492. Is it merely an artifact of the perhaps panoramic view?
In today's APOD "the planets appear to be in a straight line" because the horizon is curved.

In the 2492 simulation "the planets appear to be in a curved line" because the horizon is set as straight.

The non-Euclidean geometry of the celestial sphere requires all "parallel lines" to intersect.

However, the Euclidean geometry of your video screen allows "parallel lines" to intersect
if and ONLY if one or more of them appear to be in a curved.
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Re: APOD: Planetary Alignment over Italy (2021 Dec 19)

Post by Chris Peterson » Wed Dec 22, 2021 1:43 pm

Ann wrote: Wed Dec 22, 2021 5:31 am Impressive, alter-ego! Does that mean that today's alignment is extremely rare?
As the positions of the planets never have and never will repeat, every single instant of time represents an extremely rare alignment! They are all the same as far as the Universe is concerned- of no importance. So it all comes down to the significance we, as humans, choose to put on the patterns our brains try to detect.
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Re: APOD: Planetary Alignment over Italy (2021 Dec 19)

Post by johnnydeep » Wed Dec 22, 2021 3:34 pm

neufer wrote: Wed Dec 22, 2021 1:40 pm
johnnydeep wrote: Wed Dec 22, 2021 12:57 pm
Alright, alter-ego's exacting work above notwithstanding, why again don't the planets appear to be in a straight line in the image neufer posted showing the alignment in year 2492. Is it merely an artifact of the perhaps panoramic view?
In today's APOD "the planets appear to be in a straight line" because the horizon is curved.

In the 2492 simulation "the planets appear to be in a curved line" because the horizon is set as straight.

The non-Euclidean geometry of the celestial sphere requires all "parallel lines" to intersect.

However, the Euclidean geometry of your video screen allows "parallel lines" to intersect
if and ONLY if one or more of them appear to be in a curved.
Thanks neufer (and Chris). I think I understand now.
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Re: APOD: Planetary Alignment over Italy (2021 Dec 19)

Post by alter-ego » Thu Dec 23, 2021 2:25 am

One interesting side note. You might think the ecliptic (a great circle) should be the best-fit curve for planets. Logically, it would be for heliocentric coordinates, but from Earth, the planets' appearance against the stars is complicated by the Earth's orbit. For the 2492 planet grouping, I added the ecliptic-of-date (which intersects the sun). It's clear the magenta curve is the better fit.
 
stellarium-017.png
 
You can see the ecliptic appears curved. Within this wide-field view, only one (either one) of these two curves can "straight". Only in the limit as the FoV → 0°, i.e. arc -lengths → 0°will Euclidean geometry apply, and both arc segments will become straight.
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Re: APOD: Planetary Alignment over Italy (2021 Dec 19)

Post by alter-ego » Thu Dec 23, 2021 4:47 am

alter-ego wrote: Thu Dec 23, 2021 2:25 am ... You might think the ecliptic (a great circle) should be the best-fit curve for planets. Logically, it would be for heliocentric coordinates, but from Earth, the planets' appearance against the stars is complicated by the Earth's orbit.
...
Ok, below is the view from the Sun's equator-of-date. This version of Stellarium happens not to plot the ecliptic, but the equator-of-date is shown. It is the same as the ecliptic-of-date. In this case Mercury joins Pluto being way off from the great circle, but Earth is now part of the orderly group. Excluding Mercury and Pluto, the best-fit great circle for the 7 remaining planets does appear to be the Solar equator (ecliptic). At least it's a better fit than as viewed from Earth. From the sun, this grouping extends <100°
 
stellarium-018.png
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