APOD: Jupiter Meets Saturn: A Red Spotted... (2020 Dec 23)

Comments and questions about the APOD on the main view screen.
User avatar
APOD Robot
Otto Posterman
Posts: 4304
Joined: Fri Dec 04, 2009 3:27 am

APOD: Jupiter Meets Saturn: A Red Spotted... (2020 Dec 23)

Post by APOD Robot » Wed Dec 23, 2020 5:05 am

Image Jupiter Meets Saturn: A Red Spotted Great Conjunction

Explanation: It was time for their close-up. Last week Jupiter and Saturn passed a tenth of a degree from each other in what is known a Great Conjunction. Although the two planets pass each other on the sky every 20 years, this was the closest pass in nearly four centuries. Taken early in day of the Great Conjunction, the featured multiple-exposure combination captures not only both giant planets in a single frame, but also Jupiter's four largest moons (left to right) Callisto, Ganymede, Io, and Europa -- and Saturn's largest moon Titan. If you look very closely, the clear Chilescope image even captures Jupiter's Great Red Spot. The now-separating planets can still be seen remarkably close -- within about a degree -- as they set just after the Sun, toward the west, each night for the remainder of the year.

<< Previous APOD This Day in APOD Next APOD >>

User avatar
RJN
Baffled Boffin
Posts: 1599
Joined: Sat Jul 24, 2004 1:58 pm
Location: Michigan Tech

Re: APOD: Jupiter Meets Saturn: A Red Spotted... (2020 Dec 23)

Post by RJN » Wed Dec 23, 2020 5:45 am

The words "Last week" were changed to "Two days ago" on the main NASA APOD. We apologize for the oversight.

User avatar
Ann
4725 Å
Posts: 11372
Joined: Sat May 29, 2010 5:33 am

Re: APOD: Jupiter Meets Saturn: A Red Spotted... (2020 Dec 23)

Post by Ann » Wed Dec 23, 2020 5:49 am

Great photo! Thanks for the annotation! A few more moons of Saturn are visible. Which ones? Tethys, Rhea, Dione, Iapetus?

Ann
Color Commentator

jensenr@missouri.edu

Re: APOD: Jupiter Meets Saturn: A Red Spotted... (2020 Dec 23)

Post by jensenr@missouri.edu » Wed Dec 23, 2020 5:53 am

Y'all said that Titan is visible with Saturn, but there are two more of its moon there. There's one just to the left of the rings, and another one just above and to the left of the rings. Which two moons are those?

-- Ron

Neslon

Re: APOD: Jupiter Meets Saturn: A Red Spotted... (2020 Dec 23)

Post by Neslon » Wed Dec 23, 2020 5:56 am

This image is flipped left to right, or perhaps it was never un-flipped. (In addition to being upside down for northern hemisphere earthlings)

jensenr@missouri.edu

Re: APOD: Jupiter Meets Saturn: A Red Spotted... (2020 Dec 23)

Post by jensenr@missouri.edu » Wed Dec 23, 2020 5:58 am

Actually, I just took a closer look, and I see not four but five of Jupiter's moons there, three on the left and two on the right. And as I said earlier, three of Saturn's moons.

-- Ron

zeecatman
Ensign
Posts: 15
Joined: Fri Aug 07, 2015 7:38 am

Re: APOD: Jupiter Meets Saturn: A Red Spotted... (2020 Dec 23)

Post by zeecatman » Wed Dec 23, 2020 6:12 am

Image
I'm so pleased by all the worldwide attention the conjunction has been getting! So many of my family and friends who aren't ordinarily astronomy-focused have been talking about the conjunction and sharing pictures.

This afternoon it was clear where I live (finally!) and I was able to get a good look at the two brothers side-by-side in my 8" Dobsonian. They've clearly faded quite a lot since August, but it was still a pleasure to see them side-by-side. I'm no astrophotographer, but I wanted to share the picture I took with my phone camera through the eyepiece of the telescope anyway.

At the time I took this picture, the moons visible would have been (from left to right): Ganymede, Io, Callisto, and Europa.

User avatar
Ann
4725 Å
Posts: 11372
Joined: Sat May 29, 2010 5:33 am

Re: APOD: Jupiter Meets Saturn: A Red Spotted... (2020 Dec 23)

Post by Ann » Wed Dec 23, 2020 6:53 am

jensenr@missouri.edu wrote:
Wed Dec 23, 2020 5:58 am
Actually, I just took a closer look, and I see not four but five of Jupiter's moons there, three on the left and two on the right. And as I said earlier, three of Saturn's moons.

-- Ron
Jupiter has only got four big and bright moons, so the fifth light right next to Ganymede must be a star. Wonder what star it is?

Ann
Color Commentator

Neslon

Re: APOD: Jupiter Meets Saturn: A Red Spotted... (2020 Dec 23)

Post by Neslon » Wed Dec 23, 2020 8:00 am

it was HD191250. exciting name!

User avatar
JohnD
Tea Time, Guv! Cheerio!
Posts: 1376
Joined: Wed Feb 16, 2005 2:11 pm
Location: Lancaster, England

Re: APOD: Jupiter Meets Saturn: A Red Spotted... (2020 Dec 23)

Post by JohnD » Wed Dec 23, 2020 11:08 am

Seems extraordinary that this much vaunted sight, a 'near-single star' to naked eye, is so widely separated when magnified in a telescopic view!
I am not familiar with such views, but I expected to see them a few diameters apart, not a dozen of more.

Further to lighten my darkness, the visible moons are not on the same plane, when I thought that the planets' satellites would be more or less on the plane of their solar orbits. Is this another example of my ignorance?

User avatar
orin stepanek
Plutopian
Posts: 6451
Joined: Wed Jul 27, 2005 3:41 pm
Location: Nebraska

Re: APOD: Jupiter Meets Saturn: A Red Spotted... (2020 Dec 23)

Post by orin stepanek » Wed Dec 23, 2020 1:06 pm

GreatConjunction_Peach_960_annotated.jpg

Lovely;💫 I was wondering about the pin pricks around Saturn! Since they weren't identified; I presumed they might be stars! 8-)
You do not have the required permissions to view the files attached to this post.
Orin

Smile today; tomorrow's another day!

User avatar
RJN
Baffled Boffin
Posts: 1599
Joined: Sat Jul 24, 2004 1:58 pm
Location: Michigan Tech

Re: APOD: Jupiter Meets Saturn: A Red Spotted... (2020 Dec 23)

Post by RJN » Wed Dec 23, 2020 2:13 pm

Ann wrote:
Wed Dec 23, 2020 5:49 am
A few more moons of Saturn are visible. Which ones? Tethys, Rhea, Dione, Iapetus?
Good question! Sky & Telescope gives one way to identify Saturn's moons:
https://skyandtelescope.org/wp-content ... turn.html

E Fish
Science Officer
Posts: 105
Joined: Thu Mar 09, 2017 2:29 pm

Re: APOD: Jupiter Meets Saturn: A Red Spotted... (2020 Dec 23)

Post by E Fish » Wed Dec 23, 2020 2:15 pm

I was fortunate enough to look out when there was a break in the clouds for five minutes. I saw the conjunction and I grabbed my binoculars and verified that I was correct in what I thought I was seeing. Then, the clouds came back in and that was it. This is a lovely telescopic view.

gcal

Re: APOD: Jupiter Meets Saturn: A Red Spotted... (2020 Dec 23)

Post by gcal » Wed Dec 23, 2020 2:51 pm

Using the Sky & Telescope tool, I couldn't get the orientation to match the APOD image, so I just had to assume that Titan is the bright one, and go in order from there. S&T shows Tethys and Dione close together at that time, and I only see one dot at that place in the APOD image, so I don't know which one it is. For those who want to check S&T themselves, I won't spoil the answer; just remember to set the date.

User avatar
johnnydeep
Commander
Posts: 625
Joined: Sun Feb 20, 2011 8:57 pm

Re: APOD: Jupiter Meets Saturn: A Red Spotted... (2020 Dec 23)

Post by johnnydeep » Wed Dec 23, 2020 4:30 pm

RJN wrote:
Wed Dec 23, 2020 2:13 pm
Ann wrote:
Wed Dec 23, 2020 5:49 am
A few more moons of Saturn are visible. Which ones? Tethys, Rhea, Dione, Iapetus?
Good question! Sky & Telescope gives one way to identify Saturn's moons:
https://skyandtelescope.org/wp-content ... turn.html
Nice! The credit link to Damian Peach's twitter feed has some more discussion of the extra moons visible. The fifth Jupiter moon is apparently a star.

And from that page you linked to, and the image time of 12/21/2020 00:18UT, we get this (I couldn't get the orientation to match exactly):

Saturn Moons at Time of Great Conjunction.JPG

So, in theory we should be able to see a fifth Saturnian moon - Enceladus - just below and very close to Saturn, but it must be too dim to reveal itself in this APOD.

EDIT: even after color inverting the APOD image, Enceladus is nowhere to be found:
You do not have the required permissions to view the files attached to this post.
"To Boldly Go......Beyond The Fields We Know."

heehaw

Re: APOD: Jupiter Meets Saturn: A Red Spotted... (2020 Dec 23)

Post by heehaw » Wed Dec 23, 2020 4:46 pm

Neslon wrote:
Wed Dec 23, 2020 8:00 am
it was HD191250. exciting name!
Actually, for amateur astronomers it IS a truly exciting name: read about him here: https://en.wikipedia.org/wiki/Henry_Draper_Catalogue

De58te
Science Officer
Posts: 380
Joined: Mon Sep 30, 2013 6:35 pm

Re: APOD: Jupiter Meets Saturn: A Red Spotted... (2020 Dec 23)

Post by De58te » Wed Dec 23, 2020 5:02 pm

Of course where I live at this time in December, there were snow flurries on Sunday night, and even today it is overcast and cloudy. I noticed something though in the picture. Wonder if it is a telescopic illusion? When I went to school nearly 45 years ago we were taught that the Great Red Spot is so large that 3 Earths could fit in it. Nowadays it must have shrunk since astronomy magazines say that 2 Earths can fit in it side by side. Yet when I look at the picture, Ganymede and Callisto can appear to be large enough to fit into the GRS. Yet Ganymede and Callisto side by side is the same diameter as one Earth. Even Europa with Ganymede look like they could fill the GRS. Is this an illusion or has the GRS shrunk even more?

saturno2
Commander
Posts: 699
Joined: Wed Jun 29, 2011 10:05 pm

Re: APOD: Jupiter Meets Saturn: A Red Spotted... (2020 Dec 23)

Post by saturno2 » Wed Dec 23, 2020 10:12 pm

This image is beautiful