December 18, 2022

12/18/22
star chart for december 18, 2022

Sunday, December 18, 2022
Nick Strobel

Bakersfield College is closed for the next two weeks. The William M Thomas Planetarium closed out a successful fall schedule of shows with a sold-out showing of “Season of Light” that has become a holiday tradition for several families at least. The spring schedule will be posted in mid-January on the planetarium's website.

The Orion capsule of the Artemis-1 splashed down on December 11 right on schedule. It was a very good start to the Artemis program that will culminate with landing people in the moon's south pole region where there is evidence of water ice deposits in the perpetual shadow of crater walls. That should happen sometime in 2025. The Artemis-1 mission was an unmanned test run of all of the equipment, so it took a more leisurely pace to the moon and back. Cameras on the solar panels and inside the capsule gave us a view of what the astronauts will see on the next couple of missions. The Artemis-2 mission with 4 astronauts on board will take just 4 days to travel from low Earth orbit to the moon sometime in spring 2024. Artemis-2 will be a test run of everything but the actual landing on the moon. The landing will happen with Artemis-3.

The season of winter begins this Wednesday, December 21 with the December solstice which is when the sun reaches its southern-most position among the stars. On this day the sun will rise as far south in the southeast as it will do all year, travel across the sky on its lowest path for us in the northern hemisphere (those in the southern hemisphere will see the sun take its highest path), and then set as far south in the southwest as it will do all year. Because the sun's rays are hitting our part of Earth (in the northern hemisphere) at the shallowest angle, this is the lowest flux of sunlight all year. The sun is also up above the horizon for the shortest amount of time on the December solstice, so this day marks for us the least cooking power and cooking time of the sun. There is still some residual heat from the warmer summer, so our coldest days will probably be a bit later in the winter.

This time of year is probably the busiest shopping time of the year and that includes the purchase of telescopes. One of the chapters in my online Astronomy Notes textbook is about telescopes—the types of telescopes, the powers and limitations of telescopes, and the effects of the atmosphere on the light coming from distant objects. I end the chapter with some advice about buying a telescope for yourself or a loved one and then give pointers to review sites that'll get into the nitty gritty details of a particular telescope that has caught your eye. 

There are three things you should consider when purchasing a telescope. First is the quality of the the optics, especially the “objective”, which is the big mirror at the back end of the telescope for a reflector telescope or the large glass lens at the front of the telescope for a refractor telescope. The objective is what determines the two most important powers of a telescope: the light-gathering power and the resolving power. Magnification is the least important power of a telescope and that power can be changed with a different eyepiece. 

Second is the stability and sturdiness of the mount. You don't want the telescope wobbling about when you touch it and that wobbling is more noticeable under higher magnification. Last but not least is how easy it is to transport the telescope and set it up when you're out in the field. A telescope that is hard to set up, loses its charm quickly and tends to stay stored away in the closet or garage. Go to www.astronomynotes.com/telescop to learn more about telescopes.

Actually, one more piece of advice about telescopes is to get to know the helpful people of the Kern Astronomical Society, our local astronomy club. Pick their brain at a public star party or bring your telescope to one of the club parties. They love to share the night sky with others. See their website at kernastro.org for more details about KAS.

On the night of the solstice (Dec. 21), Mercury will be at its greatest separation from the sun in our evening sky. After that, it'll begin moving closer to the sun and it will be between us and the sun on January 7. Slowly climbing up away from the sun is Venus. On Christmas Eve, Venus, Mercury, and a very thin waxing crescent moon will make a beautiful triangle low in the southwest. The whole triangle is a bit too large to fit in the field of view of binoculars but you'll be able to get two objects at a time. On December 28, a much fatter crescent moon will be near Jupiter. Also, on that night, Mercury and Venus will pass by each other, getting as close as a thumb width from each other. A week later, on January 3, the waxing gibbous moon will be next to Mars in Taurus. Slightly dimmer than when it was in mid-December, Mars is still one of the brightest points in the sky.

I hope you have a great 2023!
— 
Nick Strobel
Director of the William M Thomas Planetarium at Bakersfield College
Author of the award-winning website www.astronomynotes.com