The Ellensburg, WA sky for the week of December 17, 2022

Saturday: Today is the start of the Saturnalia celebration, an ancient Roman festival in honor of their god Saturn, the god of agriculture and time. The holiday featured a break from work and school, a public banquet, and private gift giving. Some of these customs influenced the secular aspects of Christmas celebrations. After Sheldon hugged Penny on The Big Bang Theory, Leonard proclaimed, “It’s a Saturnalia miracle” https://youtu.be/yarNJnZw2yk. It would not be a miracle if you saw the planet Saturn today. It is two fists held upright and at arm’s length above the southwestern horizon at 6:00 p.m. Jupiter is four fists above the southern horizon at this time.

Sunday: With the Sun as low as it gets in the Northern Hemisphere winter sky, you may wish it was a little more prominent. In 2021, NASA’s Parker Solar Probe got that wish. It passed through the boundary between outer space and the region where the Sun’s magnetic field has a tight hold on the plasma that makes up the outer layer of the Sun. Since the Sun does not have a solid surface, this is as close to touching the Sun as an object can get. It is analogous to “touching” a cloud. The cloud does not have a defined surface but there is a definite boundary between “cloud” and “not cloud”. The Parker Solar Probe pierced the boundary between “Sun” and “not Sun” in 2021. For more about the mission plus short videos, go to http://parkersolarprobe.jhuapl.edu/.  

Monday: Are you disappointed because you are not going anywhere for the holidays? Why not take a (virtual) trip to outer space using Google’s new visualization tool called 100,000 Stars. It shows the stars in our neighborhood in a very good 3-D simulation. The Sun is initially at the center. If you zoom in, you can click on neighboring stars and learn more about them. Go to http://stars.chromeexperiments.com/ for the simulation. It works best on a Chrome browser.

Tuesday: Venus and Mercury are just above the southwestern horizon at 4:45 p.m. Venus is bright and fairly easy to find. Mercury is more of a challenge. But tonight is your best chance for the next few weeks because it is at its greatest distance from the Sun in the sky this orbital cycle.  This orientation is called the greatest eastern elongation. Over the next few weeks, Mercury will move toward the Sun in the sky. By mid-January, it will be visible in the morning sky.

Wednesday: At 1:48 p.m., Pacific Standard Time, this afternoon, the Sun reaches its lowest point in the sky with respect to the background stars. This point is called the Winter Solstice. During the day that the Sun reaches this point, your noontime shadow is longer than any other day of the year. Also, the Sun spends less time in the sky on the day of the Winter Solstice than any other making this the shortest day of the year. Even though it is the shortest day of the year, it is not the day with the latest sunrise or the earliest sunset. The latest sunrise is during the first week in January and the earliest sunset is during the second week in December. The Sun is at its southernmost point with respect to the background stars on the day of the winter solstice. This means the Sun spends the least amount of time above the horizon on that day. But the Sun rise and set times depend on more than its apparent vertical motion. It also depends on where the Sun is on the analemma, that skinny figure-8 you see on globes and world maps. During the second week in December, the Sun is not quite to the bottom of the analemma.  But it is on the first part of the analemma to go below the horizon. During the first week in January, it is on the last part of the analemma to rise above the horizon.

Thursday: Mars is five fists above the east-southeastern horizon at 8:00 p.m.

Friday: Just before Christmas, you look for junk to clean out of your closets so you can re-gift it. I mean, so you can throw it out or recycle it. NASA’s Meter Class Autonomous Telescope on Ascension Island is a key tool in a program tracking about 22,000 pieces of space junk. Some of this junk is dangerous. The International Space Station occasionally performs debris avoidance maneuvers to keep its panels and sensitive instruments safe. For more information about the project, go to http://goo.gl/Kxgihd.

The positional information in this column about stars and planets is typically accurate for the entire week. For up-to-date information about the night sky, go to https://nightsky.jpl.nasa.gov/planner.cfm.