Jupiter and Saturn, as shown in our “Zodiac Wavy Chart,”
keep drawing nearer to their Great Conjunction of December 21. (And Christmas draws almost as nearer, but luckily for your Christmas list the Wavy Chart for 2021 is ready!)
Here is another of the illustrations I’m managing to prepare for the dazzling conjunction, the closest in four centuries.
See the end note about enlarging illustrations.
This is a highly magnified view, as through a powerful telescope, with a field only a fifth of a degree wide. (Your little finger held out at arm’s length appears one degree wide.) Most conjunctions of bright planets and stars are much wider and pictures of this type for them would have to have 5° or 10° fields, in which we couldn’t possibly show planets at their true size. But here we do.
Physically, Jupiter and Saturn are 11 and 9 times as wide as Earth. But they are about 150 million and 1,600 million kilometers away.
In this magnified view I can also show the major satellites, though they have to be exaggerated in size or they would be too small to see. You see them, even with most optical aid, as star-like points. To avoid crowding, the inner four Saturnian satellites are labeled with just their numbers (they are Mimas, Enceladus, Tethys, and Dione).
The pictures are set for a time shortly after sunset in the USA. So on the evening of Dec. 20 Jupiter has yet to catch up with Saturn, and on the evening of Dec. 21 it has passed. The closest approach, to only about a tenth of a degree, happened during the intervening daylight for America and Europe.
But even a day away from that, the planets are close. For the naked eye, this will be a merging of two bright “stars” – magnitudes -2.0 and 0.7 – into an even more brilliant star that may seem stretched northward. In the telescope, it will be a rare chance to see two swirling satellite systems that seem almost in danger of intermingling!
Home watery planet department
Anthony Barreiro has sent me a brace of interesting articles
Rising sea levels have recently been measured with greater accuracy, taking into account the complications near coasts. The acceleration of the average world rise is greater than had been thought. It seemed to go into reverse in the 1940s and 1950s, but this was the effect of a spree of dam-building.
There will be even more accurate information, thanks to the recently launched Sentinel-6 Michael Freilich satellite, a collaboration of NASA and ESA. It might not have happened: there was a proposal by the Trump administration – fortunately rejected by Congress – to restrict NASA to “looking up” into space: that is, to stop bringing unwelcome news by surveying our own planet.
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ILLUSTRATIONS in these posts are made with precision but have to be inserted in another format. You may be able to enlarge them on your monitor. One way: right-click, and choose “View image”, then enlarge. Or choose “Copy image”, then put it on your desktop, then open it. On an iPad or phone, use the finger gesture that enlarges (spreading with two fingers, or tapping and dragging with three fingers). Other methods have been suggested, such as dragging the image to the desktop and opening it in other ways.
Sometimes I make improvements or corrections to a post after positing it. If you click on the title, rather than on ‘Read more’, I think you are sure to see the latest version.
This weblog maintains its right to be about astronomy or anything under the sun.
what about offshore oil drilling? At least Petrobras here in Brazil pumps water into the oil wells to kep pressure stable as oil flows out. So even if sea levels were to rise, offshore oil drilling should decrease it a lot
This conjunction marks an important milestone for me. In May 2000 all five planets bright enough to be seen by the unaided eye were visible in the west after sunset (including an alignment of Jupiter and Saturn on 31 May). When I learned about that I decided I wanted to see them. One thing led to another, and I’ve been seriously watching the sky ever since.
The sea level rise graph packs a lot of information into a graceful curve. The vertical axis is *not* sea height — it’s the *rate of change* in sea height. It’s greater than zero across all the years on the horizontal axis, so the seas have been rising the whole time, just more slowly when we were building a lot of dams. I failed calculus in college (too distracted by adolescent enthusiasms to study for exams), but I’m grateful to have been exposed to the concepts of velocity and acceleration. We can feel acceleration when we’re in a moving vehicle, and be alarmed when we’re accelerating or decelerating too rapidly. But we don’t naturally experience the same visceral reaction to a graph of rate of change, whether it’s in sea level heights or corona virus infections.
I tried to figure up the distances to Jupiter and Saturn for their current position, and realized I may not be remembering my trig very well. I thought I recalled the law of sines correctly but maybe I didn’t. Using the law of sines twice for each planet, I came up with about 1,453,000,000 km to Saturn right now, and 836,000,000 km to Jupiter (distances from Earth to those planets), but I don’t have a good feel for whether that is even in the ballpark. I have never been able to remember the law of cosines, it’s too complicated LOL.
My goal was to get pictures of their slow approach (the last one I got being on Nov 18 = http://www.starvergnuegen.com/astropix/2020/2020_11_18_jup_sat_index.html) up to the conjunction, but I agree with Charles Golden, it’s almost guaranteed that we’ll be clouded out on Dec 20 and 21 :)
About 886,218,000 and 1,619,398,000 km from Earth to Jupiter and Saturn on Dec 21, according to my precalculated table. Both are at this stage getting gradually more distant. I’m not sure what is meant by the laws of sines and cosines; are you starting from the angular widths of the planets:
This was my attempt to solve the “how far is Jupiter (or Saturn) from Earth?” question:
https://www.flickr.com/photos/starvergnuegen/50657916811/in/dateposted-public/
I was trying to do that because I probably misunderstood the numbers you cited in the article about the distances, and I was trying to do it from memory of my 9th grade geometry and 11th grade trig, probably with not much success LOL
I screwed up the last calculation because I used km for Jupiter but miles for the Earth! here is a link to the corrected geometry, at least I think it’s correct this time:
https://www.flickr.com/photos/starvergnuegen/50659235667/in/dateposted-public/
Some are contending for 800 year interval … https://www.msn.com/en-us/news/technology/jupiter-and-saturn-to-align-in-rare-double-planet-for-first-time-in-800-years/vi-BB1bqlPS?ocid=msedgdhp
They are already very close and appear in the same field of view in my Zeiss Mini Quick 5×10 monocular.i tend to pack this during daytime hikes when I don’t think that I will be looking for DSOs but occasionally get delayed walking back and it’s better than the naked eye and I got Uranus in it last week.
4 centuries! Impressive – and now I know that I will be experiencing rain/cloud cover on the 20th and 21st of December. ;->