Category: Astronomy

What’s special?

Omitting the orbital technicalities by a great deal, a conjunction between Jupiter and Saturn (A Great Conjunction) happens steadily over history, and humans have been keeping track of them since at least the time of Kepler. From the perspective of the sun, Jupiter takes 11.9 earth years to complete one orbit, and Saturn 29.5 years. This means that they line up roughly every

(29.5*11.9)/(29.5-11.9) ≈ 19.9 years.

Conjunction has to be able to be observed on earth to count, and this complicates matter a bit further, causing the exact moment of each conjunction event to vary by up to a few months.

From the perspective outside the solar system, we see that, when the two outer giant planets seem close together on earth, earth itself, jupiter, and saturn, almost coincide on a straight line, as illustrated below.

In reality, this line almost always point near the sun, and hence the two exterior planets are rarely well-separated enough from the sun to allow for a good observation session on earth. For example, the last Jupiter-Saturn conjunction was May 28, 2000, but this happened behind the sun. Last time Jupiter and Saturn appeared this close was July 16, 1623 — this conjunction in the lifetime of Galileo also took place behind the sun, and hence was unlikely to have been studied. In short, the previous comparable event to the one tomorrow dates all the way back to March 4, 1226 [1].

For people with a telescope, the rings of Saturn and the moons of Jupiter can appear in your view at the same moment, creating a sensation that hundreds of millions of kilometres of separation giving way to celestial coincidence.

WHERE TO LOOK?

Below are some observation tips from NASA:

Find a spot with an unobstructed view of the sky, such as a field or park. Jupiter and Saturn are bright, so they can be seen even from most cities.

An hour after sunset, look to the southwestern sky. Jupiter will look like a bright star and be easily visible. Saturn will be slightly fainter and will appear slightly above and to the left of Jupiter until December 21, when Jupiter will overtake it and they will reverse positions in the sky.

The planets can be seen with the unaided eye, but if you have binoculars or a small telescope, you may be able to see Jupiter’s four large moons orbiting the giant planet.

And here are some preliminary results that I rendered / photographed in the night of December 20, 2020.

References

[1] List of Great Conjunctions between 1200 and 2400 AD, Wikipedia

(Realize that back then nobody on earth was using the modern Gregorian calendar, so pinpointing the exact date is as much a historical venture as it is astrophysical.)

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And happy Solstice to my readers around the world. You probably won’t hear from me until 2021, so all the best in the new year. The hopes and dreams of humanity won’t just be put off by nature like this, I am fully convinced.

A bunch of sunspots has emerged following the recent conclusion of the solar minimum. Quoting one of my astronomer friends based in Western United States, a powerful solar flare now would be a fitting end to 2020… To that I say, don’t forget backing up your critical data and communication lines.

Anyways, here are two sun pictures taken between my teaching and office work this afternoon.

Speaking of the sun, this is the beginning of the third solar cycle in my life!

… And if you measure like that, human lives are comically short.

The order of nature that we find ourselves developing from, is sometimes contrasted with the order that we strive to construct for ourselves after (and despite) realising the frequent lack thereof if one is ever not careful.

I thank the language of physics for unifying my appreciations of both.

…we give little thought to the machinery that generates the sunlight that makes life possible, to the gravity that glues us to an Earth that would otherwise send us spinning off into space, or to the atoms of which we are made and on whose stability we fundamentally depend…

Carl Sagan, Introduction to A Brief History of Time, 1st Ed.

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In another recent note, 366 days ago, I turned in my honours / senior thesis, and wrote down the first paragraphs of my statement of purpose in hep-th. So much for that thought, but I am glad I kept going in physics.
— And I got to sneak into the same mathematics office again in order to recreate a one-year-old photograph. Try the new slider widget below!

What’s so bright in my eyes?

The ceiling lamp.