The Sky and ISS for December
By Chuck McPartlin
Jupiter, Saturn, and Venus dominate the early evening skies to the southwest, showing the line of the ecliptic, the plane of the solar system. At sunset on Monday, December 6, look for a beautiful slim crescent Moon, bathed in earthshine, just below bright Venus. Photo op! Venus is racing toward its passage between us and the Sun, becoming a slender crescent as it is increasingly backlit from our point of view. Even as the crescent is getting slimmer, Venus is getting closer to us, so it remains very bright.
Comet C/2021 A1 Leonard will be visible in binoculars in our predawn sky up until about December 10, rising between 1 and 4 AM PST. It will be passing through the springtime constellations Canes Venatici, Boötes, and Serpens Caput. It will reach perihelion on January 3, and then become a good southern hemisphere object. They seem to get all the comet luck these days. Unless outgassing from the comet causes a radical change in its orbit, Comet Leonard is on a trajectory that will take it out of our solar system, never to return. You can keep tabs on the comet at the following sites:
The Geminid meteor shower will peak on the evening of December 13/14. The predicted peak is at 11 PM, but a bright waxing gibbous Moon will interfere until it sets around 3 AM. The Geminids rival the summer Perseids in their hourly rate, and have a high proportion of fireballs because they are rocky fragments of asteroid 3200 Phaethon. The radiant point is in Gemini, near the head stars Castor and Pollux, and will be nearly overhead at midnight. Let's hope for clear skies!
On Tuesday, December 21, the northern hemisphere's Winter Solstice will occur at 7:59 AM PST.
As Venus departs our evening sky, it will appear as a very thin but bright crescent in binoculars at sunset on Thursday, December 30, with much dimmer Mercury just over 5 degrees off to the left.
The International Space Station will be making some nice visible evening passes between December 4 and December 11. Its orbit may change from time to time, especially now that they have to dodge more space debris, so to get the latest and most complete predictions, visit Heavens Above.
On Saturday, December 4, the space station will make a brief low pass over our mountains, starting at 6:23 PM PST in the NNW and lasting about a minute.
Sunday's pass will be a bit longer, but still low, starting in the NNW at 5:36 PM, and vanishing into our shadow at 5:39 PM in the NE, just after passing the bright star Capella in Auriga, the Charioteer. It will appear briefly in the NW on its next orbit at 7:12 PM, below Vega, and disappear in the N at 7:13 PM.
Monday will have the brightest pass of this sequence, rising at 6:25 PM in the NW, climbing through the Lozenge asterism marking the head of Draco, through Cepheus, and then fading away into the Earth's shadow high in the N at 6:28 PM.
On Pearl Harbor Day, the ISS will make a long bright pass starting in the NW at 5:38 PM, going through the bowl of the Little Dipper, then just below Polaris and through Perseus, setting in Eridanus at 5:44 PM in the ESE. Then it will show up again at 7:16 PM in the W, passing low beneath Vega to disappear above Venus in the WSW at 7:17 PM. The Moon, Saturn, and Jupiter will be nearby.
On Wednesday, it will make a similar pass, but higher and longer, starting at 6:28 PM in the WNW, passing through the assemblage of planets and below lonely Fomalhaut, and setting in the dim constellation Phoenix at 6:34 PM in the S.
On December 9, the station will go higher still, rising in the WNW at 5:41 PM, going through the Summer Triangle and above the planets to fade away in the SSE at 5:47 PM in dim Fornax.
The last evening pass of 2021 for Santa Barbara will start on Saturday, December 11 at 5:44 PM in the W, and go very low past Venus and end in Grus, the Crane in the SSW at 5:48 PM.
Visible passes by the ISS will transition into our dawn skies until mid January of 2022.