3VC-henge -- Winter Solstice Edition 

For some months I've been watching the seasonal progress of the sunlight shining through the front doors of our church, Valley View Village Church (A.K.A. "3VC").  Thankfully, it was a rare unseasonably sunshiny Ohio day on Sunday, December 22, the first full day of winter.  The Sun was at its lowest annual elevation at the meridian above the southern horizon.  The sunlight aligned perfectly with the door frame of the church doors at precisely 12:27 PM (local "High Noon" for our longitude).  

As you can see, the sunlight pattern radiated down onto the floor and extended well beyond the snow rug in a perfect "Stonehenge" alignment.  In our latitude on the shortest day, noon shadows are about twice as long as the height of the objects casting them, so the shadow of the door frame cast a very long patch of sunlight about 15 feet long.  

If you forget or get clouded out on Saturday, you'll still have a couple more chances to see the Moon high overhead during major standstill in 2025.  The Moon will reach the northern extreme again in darkness on the evening of Friday, February 6.  You can spot the First Quarter Moon in bright twilight after sunset on Friday, March 7.  

After that the lengthening days will make it hard to spot the Moon in daylight when it passes this point.  But if you have a sharp eye and are up for a "Moonfinder" challenge, you can take a look about 6:30PM on April 3 and around 5:30PM on May 1.    After that the Sun will be too close to the solstice point so the Moon will be too close and hard to spot when it passes this point. 

Whether or not there is a major standstill, the Moon passes the point of the summer solstice (and every point in its orbit) each month.  The Moon aligns with a specific point in the sky every 27.3 days.  This interval is called the sidereal month, which is the time for the Moon to make a single 360 degree circle of the ecliptic through 12 zodiac constellations, the period in between successive alignments with a single star.  This is a shorter period than the more familar synodic month, the cycle of the Moon's phases, when the Moon passes through 390 degrees of the ecliptic or 13 zodiac constellations.  All of that will be explained in detail in Measuring the Heavens.

While the Moon will be at its maximum northern declination and highest at the summer solstice point in Gemini this year, it will also be at its maximum southern declination and its minimum lowest merdian elevation when passing through the winter solstice point in Sagittarius.  On June 11, 2025, just before the longest day, we can expect to see the Full Moon in Sagittarius about 10 degrees lower than its normal spot, a mere 16 degrees above the horizon here in Cleveland.  The same will be true in July and August and into the fall.  So I plan to continue covering this rare configuration as we approach that time.     

The Opposition Occultation of Mars

We have another rare treat coming up on the evening of Monday, January 13.  The Full Moon will align with the planet Mars, which is currently blazingly bright as it nears opposition.  At this time Mars is "opposite" the Sun in the sky (hence the name) and thus at its closest point to the Earth in its orbit.  And since it's at its closest, Mars is therefore at its brightest, shining with the color of a shiny new copper penny in the evening sky.

As with all the other stars and planets along the ecliptic, the Moon swings into alignment with Mars every month in a lunar conjunction.  However, this month is more than just a regular conjunction.  On the evening of Monday, January 13 it will be an occultation of Mars, where the Moon passes in front of the planet and covers it over for a period of time.  (By the way, in spite of the similarity in the words, this has nothing to do with "the occult."  The Latin root means "hidden" which refers to the Moon covering over and hiding the planet.)           

As reported in this previous edition of this newsletter, there was a season of occultations back in 2023, including occultations of Mars.  But this one is really special since it occurs early in the evening over North America, so you won't need to stay up late to see it.  Here in Cleveland, Mars disappears at 2:12 UT, which is 9:12 PM EST.  The Moon covers Mars for more than an hour, and the Red Planet reappears at 3:12 UT, which is 10:24 PM EST.  

The durations and the times disappearance and reappearance are different depending on your location.  You can find your local times from this page at the International Occultation Timing Association (IOTA) site.  The times are given in UT (Universal Time) so here are some converters for EST, CST, MST and PST.  

Mars is currently passing by the constellation Gemini near the "twin stars" Castor and Pollux.  This is in the famous part of the sky near Orion and Taurus so you should have no problem spotting Mars before your local time of occultation begins.  Be sure to go outside a couple times well beforehand to take a look and watch the Moon as it steadily approaches Mars.  Even though the Moon is full and therefore bright, Mars near opposition is at its brightest so this pair should be a glittering sight in the night sky.  You can also take a look with binoculars or a telescope to see Mars as the Moon approaches closer.

Some astute readers might wonder how the Moon can occult this planet when it's still close to major standstill and far north of the ecliptic.  It so happens that Mars is also far north of the ecliptic at this time.  Like the Moon, Mars (and all the other planets) also has an orbit inclined to the plane of the ecliptic.  The ascending node of Mars' orbit it at celestial longitude 49.5 degrees, in the constellation Aries just east of Taurus.  So Mars is very close to its own maximum northern declination.  So this occultation occurs very far to the north. 

Please drop me a line and let me know if you are able to spot this pair next Monday night.