The innermost planet reaches farthest out from the Sun on the evening side. Unfortunately…
See the end note about enlarging illustrations.
The moment of greatest eastward elongation is Sep. 14, 4 hours Universal Time (which is back in Sep. 13 by American clocks).
Mercury is in a part of its orbit south of the ecliptic plane. So, for us in Earth’s northern hemisphere, it comes out at such a low angle to the September horizon that this is not the best, but the worst, of Mercury’s three evening excursions of the year.
In this graph, gray and blue areas represent evening and morning excursions. The top figures are the maximum elongations, reached at the top dates shown beneath. Curves show the altitude of the planet above the horizon at sunrise or sunset, for latitude 40° north (thick line) and 35° south (thin), with maxima reached at the parenthesized dates below (40° north bold).
For the southern hemisphere, by contrast, Mercury stands about vertically above the sunset horizon.
Which planetary zone is temperate?
September 14 is the 700th anniversary of Dante’s death. Besides being a poet, he engaged in the politics of the petty Italian states; he had been exiled from Florence, had been invited to live in Ravenna, and caught malaria on a diplomatic mission across the wetlands to Venice. He was 56, and had completed a year earlier the Divine Comedy in its three parts, Inferno, Purgatorio, and Paraddiso, begun in 1308.
A commemorative article in the Guardian, mainly dwelling on parallels between the factionalisms of Dante’s time and ours, mentions that “In Canto XVIII [of the Inferno], we learn that the souls of just rulers dwell in the temperate sphere of Jupiter, well away from the extremes of fiery Mars and cold Saturn.” I would have liked to quote this passage in Italian and English, but couldn’t find it; maybe you can.
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This weblog maintains its right to be about astronomy or anything under the sun.
I managed to see Mercury once during the current evening apparition. On Saturday September 4 friends invited me to accompany them to Lick Observatory on Mount Hamilton, 1300 meters above sea level. The sky was clear above the usual layer of haze in the Santa Clara Valley below, made worse this year by smoke from the wildfires. For a few minutes about a quarter hour after sunset, Mercury was a glowering red ember a few degrees above the horizon. That was it for the entire apparition! I’m hoping for clear skies for the upcoming morning apparition.
I like the idea of different heavens for different sorts of people. To each their own. But now I need to figure out which heaven I aspire to. Could we visit other heavens for variety?
From the cover picture story for my coming Astronomical Calendar 2022, about Pavo the peacock and other birds of the sky:
A bird is, one could say, the least ridiculous object to imagine as composing a piece of the celestial sphere. There could be a culture that segments the sky entirely into birds.
The smoke might make the viewing clearer. I remember a field trip to Stony Ridge Observatory in the Angeles National Forest when I was taking astronomy at Glendale College. Our teacher said that the lights of L.A. usually drown out good views but every once in a while, a marine layer covers L.A. and the viewing is superb. That happened on the night of our field trip and we had lovely views all night. Took some pictures of nebulae and galaxies. Had to manually keep the object being photographed on the crosshairs of the big telescope during the whole exposure.
Speaking of Mars, Elon Musk has a goal of regular flights to Mars carrying 100 people on each flight, by 2050. His latest launch was Wednesday. 4 civilian astronauts are now orbiting Earth at an altitude of 575 km for 3 days. By contrast, Hubble was at 540 km and the ISS is orbiting at 420 km.
Guy,
Best wishes from Bob Victor!
I forwarded your question about Dante’s writings to a friend, and here is his reply:
Tue 9/14/2021 4:31 PM
Bob,
He couldn’t find the passage about Jupiter because it’s in the Paradiso (Canto XVIII:58-99), not the Inferno. It doesn’t say in so many words “just rulers dwell in the temperate sphere of Jupiter, well away from the extremes of fiery Mars and cold Saturn”. It mentions Jupiter (an earlier canto described the heaven of Mars, I think).
The passage in English prose:
https://www.poetryintranslation.com/PITBR/Italian/DantPar15to21.php#anchor_Toc64099911
The canto in the original along with a modern Italian paraphrase (starts at 58):
https://divinacommedia.weebly.com/paradiso-canto-xviii.html
There may be more specific details elsewhere that better cover the Guardian quote but I haven’t read beyond the Inferno in English a long time ago, so I don’t really know.
Happy to help.
Charles Miller
Grazie to Bob and Charles! They shall dwell in a happy sphere (of Mercury the mesenger?).
I think I know where the souls of our leaders here in the western world are going LOL
Mercury has been looking fantastic from Sydney for the past few evenings in the western evening sky.
And re the Guardian reference from the Divine Comedy: Dante deals with just and temperate rulers in the Paradiso, not the Inferno. Canto XVIII of the Paradiso has the following quote at lines 64-69 (John Ciardi translation):
“And such a change as fair-skinned ladies show
in a short pace of time, when from their faces
they lift the weight of shame that made them glow –
such change grew on my eyes when I perceived –
the pure white radiance of the temperate star –
the sixth sphere – into which I was received.”
One of the notes accompanying this passage explains the reference to the ‘temperate star’: “Ptolemy described Jupiter as a temperate star between hot Mars and cold Saturn. Appropriately, it serves as the Heaven of the wise and just – souls who were the model of proportioned and temperate being”.
The relevant Italian text is:
E qual è ’l trasmutare in picciol varco
di tempo in bianca donna, quando ’l volto
suo si discarchi di vergogna il carco,
tal fu ne li occhi miei, quando fui vòlto,
per lo candor de la temprata stella
sesta, che dentro a sé m’avea ricolto.
The Dante passage is in the Paradiso Canto 18 that describes where the rulers go.
This site has translations to English, French, and German as well as the Italian version
http://dantelab.dartmouth.edu/reader?reader%5Bcantica%5D=3&reader%5Bcanto%5D=18
“ ‘Diligite justitiam,’ these were
First verb and noun of all that was depicted;
‘Qui judicatis terram’ were the last.”
D