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Founded January 1970
Julian Date: 2459187.16
2020-2021: LIII
THE DAILY ASTRONOMER
Thursday, December 3, 2020
Thursday, December 3, 2020
Night Sky Questions
Well, apparently the Remote Planetarium will be returning promptly on Monday. Today, we will continue the night sky calendar sequence by answering questions subscribers sent us pertaining to the night sky. Yes, the mythology will return next week, as well.
"You mentioned that the moon will occult Venus from some locations, even though for us Venus and the moon only appear close Will Jupiter also occult Saturn from some locations on December 21st?" L.B.
No. Jupiter will not appear to move in front of Saturn from anyone's perspective (at least not on Earth.) Lunar occultations of stars and planets often occur because the moon subtends half a degree in the sky. Planets appear to be significantly smaller in our sky. For instance, Jupiter's angular diameter varies from 29.8 - 50.1 arc-seconds. (Each degree contains 60 arc-minutes. Each arc-minute contains 60 arc-seconds.) Because planets are so small, a planet-planet occultation is an extremely rare event. Sometimes these events are considered transits if the foreground planet is considerably smaller than the planet it blocks.
The last such event occurred on January 3, 1818 when Venus moved directly in front of Jupiter (a transit). The next such event will be another Venusian transit of Jupiter on November 22, 2065.
Venus moved in front of Jupiter on January 3, 1818. Venus will next transit Jupiter on November 22, 2065. Planet-planet transits and occultations are exceedingly rare events.
The next Jupiter-Saturn occultation will not occur until February 10, 7541!
"What is the "false Sun?" Is that really a thing? Have you ever seen it, yourself?" L.P.
Yes, the false Sun, or Gegenschein, is a real phenomenon, albeit a rare one. This "false Sun" occurs when the dust along the ecliptic plane reflects a faint image of the Sun back down to Earth. The term "Gegenschein," literally meaning "countershine," was coined by Prussian naturalist-explorer Alexander von Humboldt (1769-1859). He had observed this "false Sun" during his voyages through South America.
I have not seen this false Sun, myself. In our light polluted age, the Gegenschein is particularly difficult to see. It does exist, however.
Prussian naturalist Alexander von Humboldt (1769-1859). He introduced the term "Gegenschein" in reference to the false Sun phenomenon. As all the images we saw of this false Sun were quite faint, we decided to use a portrait of von Humboldt, himself.
"Why don't you include information about Uranus and Neptune in your planet watch? Aren't they planets?" -T.S.
Yes, indeed, they are planets. However, Uranus and Neptune are so faint that they cannot be observed with the naked eye. (In theory, Uranus will sometimes brighten into naked eye visibility range. However, even when at its brightest, Uranus remains so faint that one would need to know its precise location in order to find it.)
Uranus and Neptune: Yes, they are planets, but are so faint in our sky that we do not include them in the planet watch.
"Typo alert. We need the rest of the sentence from the Night Sky Calendar Part III:
When he returned from the war ten years later, his Clytemnestra and her lover Aegithus....."
-J.O.
Thank you for your euphemistic phrasing. "Dunce alert" would have been more appropriate.
Here goes:
When Agamemnon returned from the war ten years later, his wife Clytemnestra and her lover Aegithus killed him to avenge the death of Iphigenia. Also slain was Agamemnon's mistress Cassandra, the Trojan princess who, being a prophetess nobody ever heeded, foresaw hers and Agamemnon's death. She warned her lover of his impending death and tried to persuade him to depart his wife's home at once, but to no avail.
My apologies for the carelessness.
"Can we see a baby picture?"
P.N.
Absolutely.
Miranda
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