All Things Being Equal
As the sun perches over the equator, spring begins
Perhaps you’ll be at lunch Thursday at 12:57pm. Or maybe you’ll be busy at work or school. At that particular time, however, the sun shines directly above the equator. That morning it rises due east, and that evening it sets directly west. This is the vernal equinox, the first day of spring for the 90 percent of the world’s population living in the Northern Hemisphere. In the Southern Hemisphere, it is the first day of fall. Regardless of where you live, your day will be more or less split equally between daylight and night.
More or less, because the earth is not a perfect sphere, it is tilted at a 231⁄2-degree angle, and its orbit around the sun is not a true circle. As a result of all this imperfection, our day of equal night and day along Chesapeake Bay was Monday, March 17. From now until the autumnal equinox in September, our days will boast more light than darkness, and our sunlit hours will continue to grow until summer solstice 13 weeks hence.
The waning moon rises a little before midnight Thursday, with golden Saturn just two degrees ahead of it. As the two shift to the west, Saturn pulls farther away, but they are still within a binoculars’ field of view high in the south at 4am Friday. Early morning Saturday the moon is less than 10 degrees above Antares, the red-glowing heart of Scorpius, the celestial harbinger of spring. By Thursday the 27th, the thin crescent moon rises just 90 minutes before the sun and is accompanied by brilliant Venus less than three degrees below.
Each year as Scorpius rises in the east, Orion sets in the west. At 9pm he is high in the southwest, but by midnight the hunter already has one foot beneath the horizon, and each night he marches farther from our view.
So for one last time, Orion is the focus of this year’s Globe at Night Campaign, an international effort to involve ordinary sky-watchers like yourself in gauging the darkness of the night sky. This session runs from March 21st through the 30th. The data help determine the effects of light pollution. Thousands of observers from all over the world have already compared their own sightings to those on the supplied star charts and uploaded their findings to the group’s website: www.globeatnight.org. Now’s your chance to join the cause.