StarTeacher December 2007

Star Teacher December 2007

It's that time of year...

Every year about two-thirds into the month of December, people in the northern hemisphere have a night that is longer than any other. That night is called the winter solstice. This year in Maine the winter solstice will take place on December 22. What does this mean for us? It means that we have a long, snowy winter to look forward to because our part of the planet is tilted away from the sun.

Imagine you are leaning over a fire roasting a marshmallow. Your forehead and nose would get much warmer than your cheeks and ears because they’re directly facing the fire. The sun and the Earth are sort of the same. The Earth is tilted as it spins in space, so for half of the year the sun shines more directly on one part of the Earth than the other. Because the sunlight is direct it is hotter and more intense. When the northern hemisphere is tilted towards the sun it’s summer. Around Christmastime, though, the northern hemisphere is tilted away from the sun, making it winter for us. On the winter solstice, the shortest day of the year, our part of the world is tilted farthest away from Sol, and the sunlight is much less concentrated.

Throughout history there have been many different ways people celebrate the winter solstice through the lighting of bonfires and candles. Holy and pagan rites have been associated with this time, and many ancient traditions continue to the present. You can find out more about them in the colorful star show, Season of Light at the Jordan Planetarium. For students and their families there are several public showings during December and a few of our other star shows between the holidays. So if a fieldtrip is not possible, get a master sheet of our Vacation Week bookmarks from the Jordan Planetarium.

Electrifying news from Venus

The planet Venus would not be a fun place to live. Its thick clouds make it extremely hot, plus its atmosphere is made mostly of sulfuric acid (not a very good thing to be breathing!). Recently scientists have found another reason why Venus would be a bad place for people to live: its atmosphere makes its own lightning!

Venus is one of only four planets whose atmosphere creates lightning (the other three are Earth, Saturn and Jupiter). It makes a lot more lightning than these other planets do, and even stranger, this lightning is different from all others. Instead of coming from water clouds like the lightning on Earth does, it comes from clouds of sulfuric acid. All this electrical activity makes it more difficult for probes and satellites to explore an already inhospitable planet, but scientists hope to continue to study the planet. In many ways it is a twin of our own planet Earth.

During December, Venus can be seen only in the mornings just before sunrise because it rises in the east-southeast ahead of the sun. It is the brightest of the planets so it can be seen long after the other stars have hidden in the bright glow of the coming dawn.

For more information please read the NASA press release.

What's Happening in the Sky this December?

9	New moon: It’s so dark the Milky Way looks a lot brighter
13-14	Geminid Meteor Shower – This meteor shower peaks at midnight. Possible the best shower of the year! Watch for shooting stars (meteors) all over the sky.
18	Mars closest to Earth in its 2 year orbit- 88 million km (54 million miles)
22	December Solstice – At 1:08 am the northern hemisphere will be at maximum tilt away from the sun, causing Maine’s shortest day and longest night of the year.
23	Full moon- Long Night Moon
24	Ursid Meteor Shower – Bundle up on Christmas Eve to see this smaller meteor shower that originates from the constellation Ursa Minor. The bright moon will wash out all but the brightest meteors.

Where are the viewable planets?

Venus	Rises in the east-southeast a few hours before the sun very bright in the southeast early in the morning. It is the brightest thing other than the sun and moon, so Venus can be seen between the snowy treetops until the sun rises.
Mars	Very bright in the sky, especially from December 18-24 when it will be closest to our planet and opposite from the sun in the sky. It will shine at magnitude -1.6, almost as bright as Jupiter. Look for it in the northeast after sunset in the constellation Taurus above Orion’s club . Its red color may be washed out by its brightness, so be careful not to confuse it with Orion’s bright red shoulder star, Betelgeuse, or Taurus’s red eye, Aldebaran.
Jupiter	Low in the southwest close to the sun. Early December it might just be seen in the bright twilight following the sun down. It has joined the birds, moving very far south in the sky, and will be out of sight in the sun’s glare by the solstice.
Saturn	Rises late in the evening at the beginning of the month, but as time goes on rises later and later. Can be found in the constellation Leo.

Planets in the Maine Sky December 2007
Click for printable pdf file (Acrobat req'd)

Winter Meteor Showers

If you don’t mind your toes getting a bit cold there’s no better time to see a meteor shower than in the month of December. It’s in this month that the Geminid meteor shower occurs. This meteor shower is one of the biggest ones there is. If you go outside on the days when it’s at its peak (the thirteenth and fourteenth of December) you can expect to see up to 60 meteors an hour! Here is an elementary activity for learning about METEORS.

Meteor showers usually get their names from the constellation where they seem to come from. The Geminids is no exception. Use a star map to help you find the constellation Gemini. During December at about nine o’clock you will find it low on the eastern horizon. Look for two bright stars close together. Those stars are Castor and Pollux, the heads of the twins from Greek mythology. You’ll have to stay up late to see the shower at its peak, but even earlier in the evening you can still see some meteors. See our January issue for another good shooting star event....

For a serious meteor showerer, recording the track of each shooting star is an exercise that helps to identify the point of origin of the shower. On a star chart, simply trace the path that each meteor follows from th epoint where it was first seen to the point where it disappeared. By extending the trace backwards, for several such sitings, the point of origin will appear as the radiant where they all cross. The star chart has to contain the radiant so use on that has the constellation Gemini on it such as this one. GEMINI CHART

Maynard F. Jordan Planetarium, 5781 Wingate Hall, Orono, ME 04469-5781

Phone: (207) 581-1341