First month brings events of astronomical proportion

A double New Year's Day, a Quad meteor shower, Earth at the turning point and the occult — these are just a few of the astronomical events that will occur in January.

Today is New Year's Day, but only according to the Gregorian calendar that we use. There are many calendar systems in use today, and they don't all agree when the year begins. All calendars have their roots in astronomical phenomena.

In prehistoric times, there were only a few natural events that recurred on a regular basis. The period from sunrise to sunrise, the most obvious naturally occurring interval, defined our day. The cycle of the moon from new to full to new again signified the passage of one month, or "moonth,” with the four phases dividing the month into four weeks. The sun's rising position along the eastern horizon changed from well north of due east, with long, hot days, to equally far south, with short and sometimes frigid days. This natural cycle took about 365 days and is the basis of our year.

Cultures picked different astronomical events to mark the start of the year. For some cultures, the year started when the sun rose due east, what we now call the vernal equinox or the beginning of spring. This will occur March 19 this year.

Many more cultures defined the start of the year with the sun's most southerly position, the time of the shortest days and coldest weather. We call this the winter solstice. Due to various changes in the calendar over the millennia, we now start the Gregorian calendar year Jan. 1, more than a week after the solstice. So, today is our New Year's Day.

Some cultures, notably cultures east of the Mediterranean Sea, used a lunar-based calendar. They defined the year as 12 lunar cycles. But since that corresponds to about 354 days, they usually added an 11-day holiday period or mini-month so that the moon and the sun calendars would coincide. Some cultures didn't even bother with that, keeping a purely lunar calendar, such as that still used by Muslim cultures. Jan. 10 is the Muslim New Year's Day, the start of year 1429 A.H.

Time for a shower

A meteor shower occurs when Earth passes through the orbital path of a comet. Comets are frozen balls of water, methane, ammonia, carbon dioxide and ethanol ice. The ice balls, typically a few miles across, also contain many small bits of rock and metal frozen in them. When one of these ice balls approaches the sun, the 10,000-degree heat vaporizes a layer on the comet's surface, releasing the trapped rocky and metal bits, typically about the size of peas or smaller, which spread out along the comet's orbital path. When Earth slams into this cometary debris, a large number of bits enters our atmosphere at speeds up to 150,000 mph and burn up from friction with the atmosphere — something we see as a meteor shower.

If you drive through a snowstorm, you'll notice that the snowflakes appear to come at you, even though they are falling down. This is due to your motion as you travel through the snowflake "debris.” It's looks as if all the snowflakes come from a single point directly in front of you.

This same optical illusion also occurs when Earth moves through cometary debris; the resulting meteors all appear to come out of the same point, the direction in which our planet is moving. We call that point the meteor shower's radiant, and it's named after the constellation it appears to lie in. On Friday, our planet will enter such a debris stream at midnight Central Time. The radiant appears in the constellation that we today call Bootes but was formerly known as Quadrans Muralis. This shower goes by the name of the Quadrantid meteor shower, after the old constellation name. It's a good shower, but a brief one.

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