Celebrating the spring equinox

The day we have all been waiting and wishing for is near. Saturday, March 20, is the date of the vernal, or spring, equinox. The first day of spring in the northern hemisphere.

That is the day the sun crosses the celestial equator from the south to the north bringing more direct, and hopefully warmer, sunshine to us folks north of the equator.

Thanks to the pesky 23.5 degree tilt in Earth's axis, one half of the planet leans toward the sun for half the year while the other half leans away from the sun's warmth.

Equinox is a Latin word meaning "equal night." With the sun over the equator the length of night and day would seem to be equal. But such is not the case for those, like us, living away from that central location.

The farther north, or south, of the equator you live, the day of equal night and day will vary by several days on either side of the equinox date.

Just as the vernal equinox starts spring in the north, it starts autumn, or fall, in the southern hemisphere. Down there summer has been holding forth and is now coming to an end as the sun travels north, and thus away, in their skies.

In many places these events are called the March and September equinoxes to get away from the idea that "spring" starts in March everywhere, as it clearly does not.

One curious thing can be noted however, on the equinox days the sun will seem to rise directly over the center line of any east/west highway. If you are out early on that date try it and see. At sunrise on March 20, the sun will be centered over the middle of the highway.

If you, like me, don't like getting up early try it in the evening when the sun sets, it will likewise be over the centerline of any east/west running roadway. That is just another useless piece of trivia you can tuck away for your next bit of party conversation.

If you are a micro-manager, like some folks, run outside at 11:32 a.m. on Saturday, March 20, and jump in the air to welcome spring. That is the exact time the sun will cross the equator.

SKY WATCH:

There are a couple of very interesting things occurring this week. Saturday evening, March 20, the moon will be visiting the Pleiades star cluster and will be a gorgeous, not-to-be-missed sight in binoculars. Sunday, March 21, Saturn will be at opposition, or opposite the sun in our sky. It will rise at sunset and set at sunrise giving us the whole night for observation. Any telescope will show the rings which are opening wider. On Wednesday, March 24, look for the moon again, this time playing tag with the planet Mars and M44, or Beehive, star cluster in Cancer the Crab. Binoculars will show both Mars and M44 just left of the moon. The star cluster will be about 12 degrees away, just beyond the average binocular field of view width. Just find the moon, move left to Mars, then further left to the star cluster.

NEXT TIME:

More astronomical blathering.