Orion and Sirius, 2020 January 1
Imaged from Mollusk, Virginia with a Canon EOS Rebel SL2 DSLR
and a Omegon MiniTrack LX2 mechanical star tracker
The Moon wanes as she takes a southward course through the rising springtime constellations this week. Last Quarter falls in the 13th at 6:01 am Eastern Standard Time. Luna begins the week among the stars of Leo, the Lion. If you are up late on the night of the 10th you can watch the Moon rise close to the bright star Spica in Virgo. She will glide just north of the star during the wee hours of the 11th. By the end of the week, early risers can see Luna pass through the “head” of Scorpius, low in the southeast as morning twilight begins.
We are entering the time of the year when the length of daylight increases by more than two minutes per day. On the 8th, here in Washington, we will see 10 hours 30 minutes span the time from sunrise to sunset, one hour longer than the duration on January 1st. By March 1st we will see another 50 minutes of daylight, a sure sign of the coming of spring.
Most of us are probably not very aware of the slow changes that are characteristic of the passing of the seasons. We are so regimented by our modern timekeeping methods that we tend to overlook the rhythms of the natural cycles that we have adapted into clocks and calendars. I am as guilty of this as anyone, but I do try to take a few moments each day to notice the timing of some of these cycles. I am not a “morning person”, but I am aware of when the Sun comes up. During the dark days of winter I rise in darkness each morning, craving that first cup of coffee. Now the brightening morning twilight gently wakes me, and I don’t require a jolt of caffeine to start my day.
A more subtle cycle occasionally catches me by surprise. Although all stars rise four minutes earlier every 24 hours, the subtle change of the constellations will often catch me off guard. Such was the case last night, when I was trying to take images of the “green comet”. I finished my session at around 11:00 pm, and as I was carrying my telescope back to the house I noticed Orion hanging in the southwestern sky, a position that I usually associate with spring evenings. There was a time, not all that long ago, when people were more aware of the sky and its changing patterns through the year and were literally able to tell time by the stars. Now we rely on the vibration of cesium atoms to define our daily rhythms. Most of us are unaware of the beacons that have defined our sense of time and space for millennia.
The ancient Egyptians defined our concept of the 24-hour day based on the meridian passage of 24 bright “Decan Stars”, and the most important of these was the star that they called Sothis. Today we know it as Sirius, and it is the brightest star in the sky. Pre-dynastic Egyptians noticed that when the star rose just before the Sun it signaled the time of the annual life-giving Nile flood. They established a “Sothic calendar” based on this event, which effectively defined the “tropical year” of just under 365.2422 days. However, their “civil” calendar consisted of 12 months of 30 days each, so the “First of Sothis” quickly got out of step with civil dates. The two calendars came back in synch after about 1500 years. These events were cause for great celebration, and the Egyptian civilization lasted long enough for it to be celebrated three times.
Venus climbs higher with each passing evening. She is steadily working her way towards Jupiter and will meet up the giant planet by the end of the month. Venus will continue to become more prominent through late spring, when her dazzle will dominate the western sky long after Jupiter is gone.
Jupiter is still bright in the early evening sky. You have until around 8:00 pm to get a good look at him through the telescope before he drops into more turbulent air. He sets at around 9:30 pm.
Mars still holds a prominent place, shining down from near the zenith as evening twilight fades. This week he receives a visit from Comet C/2022 E3 (ZTF), the “green comet” that has been attracting considerable press lately. If you are out at a dark location on the evenings of the 10th and 11th you can see the comet in binoculars as a fuzzy patch of light within two degrees of the red planet.