Winter solstice arrives today – don’t forget your party hat

The winter solstice occurs today Dec. 21 at 11:30 p.m. CST when the sun reaches its lowest point in the sky for the year. Photo: Bob King

If you yearn for more sun and less darkness, you’ll get an early Christmas gift today. At 11:30 p.m. Central time, the sun hits bottom in the sky, hesitates a moment and then resumes its slow journey northward to summer’s endless days. Happy winter solstice!

The solstice, literally “sun stands still”, marks the beginning of winter and day of the year with the least amount of daylight for those living in the northern hemisphere. The standing still part stems from the fact that around the solstice the sun moves very little north or south compared to the spring equinox, when it’s climbing steadily north with every passing day. This causes both the sun’s height above the horizon and length of day to change very slowly over the next couple weeks.

The path the sun takes in the sky is caused by the tilt of Earth's axis (see diagrams below). In summer, the sun rides high and days are long; in winter its path is much closer to the horizon and days are short.

Here in Duluth, Minn. the day is a lean 8 hours and 32 minutes, barely long enough for tanning. I shouldn’t complain. At the Arctic Circle, that invisible circle of latitude at 66.5 degree north, the sun won’t even bother to rise on the solstice. North of there, the sun remains below the horizon longer and longer until we reach the North Pole, where it hasn’t shown its face since the fall equinox and won’t return until the first day of spring.

As you’re probably well aware, the South Pole experiences the exact opposite season. While we relish our precious allotment of daylight here in the North, Antarctica researchers are enjoying the midnight sun on what for them and the rest of the southern hemisphere is the summer solstice.

You’ll notice that the solstice occurs late on the 21st at 11:30 p.m. for the Midwestern states. For the Eastern U.S., Europe and much of the rest of the world, that switches over to the morning of the 22nd. The date of solstice varies not only because of what time zone you’re in, but also because a full revolution of the Earth around the sun takes 365 1/4 days rather than a nice neat 365. That quarter day is the reason we have to add a leap day every four years to our calendar – as we will in 2012 – otherwise the dates of the seasons would drift. Without leap days, after only 100 years, the calendar year would be 25 days ahead of the seasonal year, making the winter solstice begin in mid-January. We don’t want that to happen.

Still that extra 1/4 day and leap year days cause the seasonal start dates to vary by several days over a cycle of 400 years. The combined gravitational effects of the planets on Earth also cause a slight shifting of the season starts over centuries of time. Precession , which is the small cyclical wobble of the Earth’s axis caused by the gravitational attraction of the sun and moon on our planet’s equatorial bulge, also plays a part. Put it all together and the date of winter’s start can vary from December 20 to December 23. The outer dates – 20th and 23rd – are rare compared to the 21st and 22nd. The last Dec. 23 solstice occurred in 1903; the next happens in 2303. The next December 20 solstice won’t be until 2080. You can read more about the seasons and Earth’s orbit HERE.

The tip of Earth's axis causes the northern hemisphere in winter to face away from the sun and toward it in summer. Credit: NASA

Of course the changes of season are caused not by Earth’s varying distance from the sun but rather by the 23.5 degree tip of its axis. During winter, the northern hemisphere is tipped away from the sun, making it appear much lower in the sky with shorter days the consequence. Less sunlight means colder temperatures and snow instead of rain. In summer the situation is reversed and days are long and hot.

The winter solstice, a time of darkness but simultaneously holding the hope of returning light, never fails to bring out mankind’s party spirit. We string lights, put green trees in our homes, sing around the blazing bonfire and beat drums. Many towns across the world hold winter solstice celebrations. Tonight Dec. 21 starting at 5:30 p.m. at the lighthouse along the waterfront in Two Harbors, which is located a half-hour north of Duluth, Minn., the good folks there will hold their annual winter solstice celebration. It begins with a candle lantern launch and a torchlight procession to the bonfire in honor the event’s founder Ellen Anderson, who passed away recently. If the sky is clear, several amateur astronomers from the Arrowhead Astronomical Society will be on hand with telescopes to look at the night sky. All ages are welcome to join in the fun.

This entry was posted in Uncategorized and tagged , , , , by astrobob. Bookmark the permalink.
Avatar of astrobob

About astrobob

My name is Bob King and I work at the Duluth News Tribune in Duluth, Minn. as a photographer and photo editor. I'm also an amateur astronomer and have been keen on the sky since age 11. My modest credentials include membership in the American Association of Variable Star Observers (AAVSO) where I'm a regular contributor, International Meteorite Collectors Assn. and Arrowhead Astronomical Society. I also teach community education astronomy classes at our local planetarium.

21 thoughts on “Winter solstice arrives today – don’t forget your party hat

  1. So with me being in california..when does it start here?.. and are there any bad effects that could happen or is this the same every year?

  2. Also bob…im starting to get super nervous about it being 2012… Any helpful words that will help me think otherwise..?? As soon as I feel positive about the world not ending on dec 21 2012… Something always gets said and makes me feel worse again..what is ur take on it??

  3. Great article, Bob. I love reading articles on the ‘mechanics’ of the earth’s movements round the sun. I think an understanding of these movements is what’s missing in those who panic any time there’s some new Youtube video that screams ‘pole shift’, a ’tilting moon’, a ‘moon out of place’, etc. I’m sure you know the sort of video I’m referring to.

    If people would only take the trouble to actually learn how the earth moves and what the intriguing consequences are, they’d be far more fascinated with its complexity than they are with the stories of doom and gloom – and wouldn’t suffer the sleepless nights or depression that come as a consequence of believing hype over fact.

    • Carol,
      Thanks – I’m glad you enjoyed it. I agree that if more people did pay attention or make the small effort to know the basics of celestial movements, what comets are and how asteroids orbit the sun, they’d pay less attention to the latest crazy flavor. The real thing is amazing in itself.

        • Hi Edgar,
          I see what you mean now. You’re referring to brightness. While Betelgeuse is a variable star, I checked on the AAVSO website and variable star observers aren’t reporting it any brighter than usual. It varies about one magnitude between 0.2 and 1.2. Right now, it’s about 0.5.

          • Edgar,
            Color perception can vary depending upon brightness (brighter usually weakens a color, fainter makes it look redder). If Betelgeuse were fading, I would expect the red color to be more obvious, but magnitude estimates by variable star observers back into September don’t indicate any fading. Other factors affecting color perception are expectations, weather and especially how long you stare at a red object. For me, a quick look shows a star’s red color better than a longer one. It’s possible but unlikely Betelgeuse’s intrinsic color has changed in such a short time by a amount large enough to be detected by the eye. The only way to be certain is to telescopically measure what’s called its “color index” through a set of different color filters. If the color index is changing, then you’d know for certain the star’s real color is changing. Is your friend a casual skywatcher, professional astronomer or?

    • Les,
      Yep, that’s the one, but if it does explode as a supernova, it could happen tomorrow or 10,000 years from now. No one knows when. No bad effects are expected on Earth since Betelgeuse is 640 light years away, but it will certainly become the most brilliant thing in the sky beside the sun and moon.

  4. Okay so now we have that.to worry about??? Why is it s unclear as to when it will explode…so it will be as big as the sun amd moon???

    • Les,
      Certainly not as big. It would look like a very brilliant star, something like Venus but brighter. Whether and even if it will explode is unclear because no one can predict exactly when a star will do this or that – only the probability of it happening. After all, we can’t predict the weather more than three days in advance and even those forecasts are often flawed.

Leave a Reply

Your email address will not be published. Required fields are marked *

*

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>