December marks the beginning of winter in the northern hemisphere. That will happen at 11:48 p.m. on Monday the 21st. The winter solstice is the lowest point that the sun will reach in the sky for any given latitude on earth. The word solstice means “sun stands still” which is what it seems to do for a few days at the lowest point of its continual arc through our sky.

If you could photograph the sun at noon every few days throughout the year, you would see it traces a figure eight in the sky, called the analemma. This giant graph in the sky is loaded with information if you know how to read it.

The analemma tells you the tilt of the earth, that we are orbiting in ellipses, your latitude on earth, sunrise and sunset times, the equation of time, when we are moving faster and slower around the sun, and many more things. If the earth was not tilted and our orbit was a perfect circle, the whole analemma would just be a single dot in our sky because the sun would always be at the same place at noon.

From the North Pole, you can only see half of this analemma because the sun doesn’t rise at all for half a year. By the time you get down to the Arctic Circle, you can see the whole thing – it is upright and each loop is the same size. Then it gets more and more tilted over and the top loop gets smaller. By the time you get to the equator, it is completely horizontal. Then the top loop gets larger and it starts tilting the other way as you get farther south until it is upright and even again as you get to the Antarctic Circle. Then part of it starts disappearing again, as above the Arctic Circle.

You can actually measure the tilt of the earth for yourself at either of the solstices by just measuring the shadow of a level stick and knowing your latitude. You could even trace the entire analemma on the ground with a sundial, which is much easier than photographing it in the sky over a year.

Exciting highlights abound again this month, making it well worth it to brave any cold weather we get. Getting up an hour or so before sunrise for several mornings this month also will reap great rewards for you, as it did for me last month.

Our four brightest planets will all grace our morning sky this month, the Geminid meteor shower will happen without the moon in the way, a lesser meteor shower called the Ursids will peak near the solstice, a new comet will be visible in the morning sky, and the moon will occult Venus in the daytime sky on Dec. 7.

Jupiter starts the month rising about half an hour after midnight and will end the month rising two hours earlier. Mars rises next, around 2 a.m., and it will only rise about half an hour earlier by the end of the month. Then brilliant Venus rises around 4 a.m. and Saturn will join the trio by the middle of the month, rising only about one hour before sunrise.

So there you have your morning planetary lineup along the ecliptic plane of our solar system. To add some real drama, watch the last-quarter moon pass near Jupiter on the third and fourth, then close to Mars on the fifth and sixth, and then very close to Venus on the morning of the seventh about one hour before sunrise. Later that day, as the waning crescent moon creeps ever closer to our brightest planet, it will actually cover up Venus completely starting at 12:40 p.m. Then the waxing gibbous Venus will reappear from the moon’s dark limb, which will be invisible in the daylight, about one hour later, at 1:40 p.m. This shows you that the moon is always moving eastward in our sky at the rate of half a degree per hour.

I’ve seen an event like this before. It’s quite amazing to witness and it really demonstrates many interesting aspects of the relative sizes and motions of neighboring objects in our solar system, and the great excitement of trying to capture it on film. You will need a telescope or a good pair of binoculars to see this daytime event.

The best meteor shower of the year, the Geminids, will peak a week later on the morning of Monday the 14th. They are expected to reach 120 meteors per hour – a fantastic rate of two meteors per minute. They are one of only two annual meteor showers that are caused by an asteroid instead of a comet. The Geminids are caused by 3200 Phaethon, which is named after the son of the sun god Helios.

All of these meteors will appear to emanate from the constellation of Gemini the Twins in the famous winter hexagon, just above Orion. It will be high in our eastern sky by 11 p.m., but you will be able to see meteors anywhere in the sky all night, as well as the next night and even some on the night of Saturday the 12th. Just bundle up, find a good open sky by the ocean or a large field and enjoy a great, quiet show brought to you by nature, and our protecting and life-giving atmosphere. If you watch for at least an hour, you can even do a scientific meteor count for the International Meteor Organization.

A comet named Catalina, discovered by the Catalina Sky Survey in Arizona on Halloween two years ago, just reached perihelion last month and will climb higher into our morning sky near all the planets all month and into next month. This comet is zipping along at 100,000 miles per hour and is already sporting two tails, one of which is 500,000 miles long. It should become visible without binoculars early this month.

See how soon you can spot it and photograph it with all of our solar system neighbors in the morning sky.

DECEMBER HIGHLIGHTS

Dec. 2: On this day in 1974 Pioneer 11 flew by Jupiter. It is now past the heliosphere.

Dec. 3: Last quarter moon is at 2:40 a.m.

Dec. 4: The moon passes just below Jupiter this morning.

Dec. 5: The moon passes near Mars this morning, one hour before sunrise.

Dec. 7: The moon passes very close to Venus this morning and will occult the planet this afternoon, starting at 12:40 p.m. and ending one hour later.

Dec. 11: New moon is at 5:29 a.m. Annie Jump Canon was born on this day in 1863.

Dec. 13: The Geminid meteor shower peaks tonight and into the next night.

Dec. 14: Tycho Brahe was born on this day in 1546, three years after Copernicus died.

Dec. 17: On this day in 1903 the first powered flight was accomplished by Orville Wright. We flew to the moon less than 66 years later.

Dec.18: First-quarter moon is at 10:14 a.m.

Dec. 21: The winter solstice happens at 11:48 p.m., marking the longest night of the year.

Dec. 23: The Ursid meteor shower peaks, emanating from Ursa Minor near Polaris.

Dec. 25: Isaac Newton was born in 1642. Full moon is at 6:11 a.m. This is also called the Long Night Moon or Moon Before Yule if it happens before Christmas.

Dec. 27: Johannes Kepler was born in 1571. He discovered the three laws of planetary motion, one of which you can see demonstrated in the shape of the sun’s analemma. He worked closely with Tycho Brahe, the greatest observer in the world at that time.

Dec. 28: Arthur Eddington was born in 1882. He led the solar eclipse tour in 1919 that was the first concrete proof of Einstein’s general theory of relativity, which came out exactly 100 years ago in 1915.

Dec. 29: On this day in 1980, the first space shuttle, STS-1, left the Vehicle Assembly Building and was rolled out to the launch pad in Cape Kennedy.