Happy New Baktun And A Joyous Solstice To All

Circumscribed halo around last night’s half moon. Photo: Bob King

Today the Mayan calendar rolls over to a new Baktun or 144,000 day cycle as it has for centuries. Coincidentally, it’s also the first day of winter in the northern hemisphere and summer for folks down under. Winter tiptoed in at 5:12 a.m. (CST) this morning while many of us were snug in our beds. Looking out my window, the world looks much the same as it did yesterday – with a difference. It’s sunny!

Come join Duluth’s celebration of the solstice at the University of Minnesota-Duluth’s planetarium.

That means a clear sky tonight and a chance to celebrate the new season. If you live in the Duluth, Minn. region, the Marshall Alworth Planetarium will feature a special “End of the World – Winter Solstice” party with shows on the half-hour in the dome, telescope viewing, pizza, cider, a raffle and a free 2013 calendar. Cost is $8 per person or $15 per family. The event starts at 6 p.m. and runs until 9. More information HERE.

Only 8 hours and 32 minutes separate sunrise and sunset in Duluth, Minn. today. The rest belongs to the night. Solstice is combination of two Latin words – sol for sun and sistereΒ to stand still. That’s what it feels like for a week or two at the time of the summer and winter solstices, when the sun reaches its highest and lowest points in the sky.

The seasons are caused by the 23.5 degree tilt of our axis. In summer, Earth’s north polar axis is tipped toward the sun, causing it to appear higher in the sky and making for longer days. Half an orbit later in winter, the north polar axis is tilted away from the sun, making for a low sun and short days. In spring and fall, the axis is tilted neither toward nor away and day and night are equal. Credit: Tau’olunga with additions by Bob King

On Dec. 21 the sun reaches its lowest altitude above the southern horizon at noon for the year. Here in Duluth, that’s about 20 degrees or two fists held at arm’s length. For Chicagoans, it’s 25 degrees, a bit higher. But if you live in Anchorage, the yellow orb of day climbs to just under 6 degrees before slinking back toward the west. My dear brother Mike who lives there must wait until 10:14 a.m. for the sun to rise today. With sunset at 3:42 p.m., he’ll need to be vigilant to catch sight of it. Buildings and trees could easily block the sun from view. .

Excellent, short video on how the seasons happen

These extremes of daylight and night are brought on by Earth’s tipped axis. If it ran straight up and down, much as Jupiter’s axis does, sunrise and sunset times would barely vary for your location. The sun would rise in the east and set in the west 12 hours later every day of the year. No variation and no seasons. Who wants that?

Thanks to the Earth’s tipped axis we experience the joys winter and the ice it brings. These are air bubbles trapped in pond ice near my home yesterday. Photo: Bob King

The tip ensures that the northern hemisphere of the planet tilts toward the sun in the summer and away in the winter. As a consequence, the sun appears very high in the sky in summer. Its longer, steeper path naturally means longer days and more intense heat. In the winter, we’re tipped away from the sun. Slanted, less intense solar rays and short days follow.

Vesta shown at 9:30 p.m. (CST) every 5 days now through Jan. 10, 2013 as it glides near the Hyades cluster. 97 Tauri is mag. 5. Β Stars shown to 7.5 magnitude. Created with Chris Marriott’s SkyMap software

If you’re looking for an interesting astronomical treat in the night sky this solstice, face east anytime during the evening hours and find the brightest “star” you can see. That’s the planet Jupiter. Just below Jupiter is the bright star Aldebaran and a V-shaped pattern of stars called the Hyades star cluster. Not far from the cluster is the famous asteroid Vesta. You’ll recall it was was orbited and studied by NASA’s Dawn spacecraft this past year.

Vesta shines at magnitude 6.5 (just under the naked eye limit), as bright as it gets this year. The star-like asteroid is super easy to see right now in binoculars, especially with Jupiter to help point you there. Take a look the next clear night.

16 Responses

  1. leslie

    Well uncle Bob… You were right once again. Your so awesome to help, talk, inform and put up with all our fears and questions!! Thank you so much!! People asked me where I got my info from and said ..ooohh my Uncle Bob from Minn. πŸ™‚

  2. thomas s

    hi Bob, the hysteria (in some circles) re 21 Dec and the Mayans was pathetic but also hilarious. tuned into the Hist Channel last nite to see what, if anything, they might say about the Mayans. 90 percent junk and about 10 percent informative. too bad: most of what they had to say was either laughable or for those who take this stuff seriously, probably got them more riled up than they might otherwise have been. and in case you want to join the survivalists, there’s a survivalist school in Arkansas that will tell you how to survive in the wild in case civilization crashes (they featured that too). thought I should share this vital info with you. seriously, all the best for the Holiday season. and have you ever thought of setting up a blog on the Patch sites?

  3. Jim Schaff

    Hi Bob,

    Did you get out viewing last night? At the planetarium End of the World party, the seeing was getting up to Florida quality- so much detail. What a treat last night was.

    This morning I saw the comet and my first look a Saturn in the morning sky- cool. The comet has a nice little tail which was easy to see in a six inch scope. It has been a good Baktun so far.

    Wish you and your family a Merry Christmas and a happy New Year.


    1. astrobob

      Merry Christmas Jim! Wish I had the chance to observe, but couldn’t because I was out in northeastern Wisconsin visiting a friend.

  4. Lynn

    Hi Bob
    Glad Friday is all over with and I bet you are too and hopefully a lot of people will learn not to trust doomsayers again and trust what the real scientists tell them.
    Some good news today, 2011 AG5 impact for 2040 has been ruled out now, which is great, but there is two other asteroid’s on the JPL impact table and the torino scale is at n/a, why is that. Thanks Bob πŸ™‚

  5. Gary Morris

    Hi Bob, Merry Christmas

    Great post showing and explaining the winter solstice. Each winter solstice I read explanations on why the day is shorter and how our angle to the sun changes our length of day. Even with all the videos and drawings I’m still not understanding. I see how days are shorter or longer because of the tilt but why is the sun so low in the south in the winter and so high in the summer. If our orbit around the sun stays the same should the sun not stay in the same position as we see it. Not sure if you can help me with this but I’ll keep trying.

    Thanks for sharing all your knowledge.


    1. astrobob

      Thanks Gary. This is a little crazy, but for the sake of explanation, picture the Earth “bowing” (as in bowing before the queen) toward the sun in summer. The queen’s head or sun in this picture is high above you. In winter, imagine bending backwards. As you do, the sun drops to the lower half of your field of vidion. Summer days are long because the sun has a long climb to make before it gets to that high point (noon) and a long time to drop back down to its setting point in the northwestern sky. The climb up and down takes many hours. In winter it has so little to climb, the sun’s up and down in just a few short hours. Does this help?

    2. Gary

      Bob, you must have known we Canadians were British subjects. Your example makes perfect sense and I’m working throught it. I’m still trying to visualize the sun and how it sits so high/low in the south. Still working on it,


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