By Vernon Whetstone
In addition to the weather, the sky is setting up for spring as well. The long awaited season has its start officially at 5:21 p.m. MDT on Sunday, March 20. That is the date of the vernal, or spring, equinox.
Equinox refers to the supposed equality of day and night. However, if you are watching your clock you will notice that day and night are not exactly equal on that day unless you are living on the equator.
The difference comes from your location on Earth’s surface. We here in southwest Nebraska are located exactly on the 40th parallel, or 40 degrees north of the equator. In fact, the line of 40 degrees north is the state boundary between Kansas and Nebraska.
There is a spot just a little west of where I reside where the three state boundaries of Kansas, Colorado, and Nebraska meet. It is out in the middle of a cow pasture and is marked with an official U.S. Geodetic survey marker and can be visited if one has the inclination.
Now, back to our time consideration. The point at which day and night are both 12-hours long for the good folks here in this area occurs between March 17 and 18. The day length of March 17 is 11 hours and 58 minutes and the day length of March 18 is 12 hours and one minute.
You can get your own chart of day length at www.sunrisesunset.com. Click the “customize” option, choose your state and then your city. Other options are also available. Such as sunrise and set, moonrise and set, and times of twilights.
The chart with Sun rise and set and Moon rise and set times is helpful when trying to maximize your observing time.
On the day of the equinox, however, you will be able to view the Sun rising and setting exactly east and west. Well, almost exactly east and west, remember that “40 degree north” thing.
It will throw the directions off a little, but it will be close enough. Find a highway running directly east and west and try it out.
SKY WATCH: First quarter Moon, March 12. There are lots of conjunctions to view for the coming week. Planets, planets and the Moon, and the Moon and some stars.
Tonight, Wednesday, March 9, look west about a half-hour after sunset for tiny Mercury and the distant gas giant Uranus. Binoculars will be essential as both the small bright dots representing the planets will be near the setting Sun and deep in its glare. Remember not to look directly at the Sun, it will be fatal for your vision.
Thursday night, March 10, check about an hour after sunset in the west for a delightful slender crescent Moon just below the Pleiades star cluster. The next night the Moon will move to just up and right of bright Aldebaran in Taurus, the Bull.
Sunday, March 13, we will all observe the beginning of Daylight Saving Time. Remember to move your clocks ahead one hour (spring forward) on Saturday evening before going to bed.
Starting on Sunday, March 13, check the western sky a half-hour after sunset and watch for the next three evenings as tiny Mercury starts a dance with its big brother, Jupiter.
Mercury is beginning what will probably be the best showing of the year. It will be higher in the sky each evening for the next week or so giving us more time after sunset to view the elusive little planet.
On March 17, the planetary probe Messenger will enter orbit around Mercury to stay and conduct scientific examination of the planet’s surface. Something earthbound telescopes have been unable to do.
NEXT WEEK: More astronomical blathering.