Change dominates the Pacific Northwest skies in March. We feel it in the air, see it on our clocks and we can watch it in the heavens above. Wandering planets, including our own Earth, combine to dramatically change the appearance of our night sky this month and at least one invention of man changes when we see it.
Daylight savingsSunset occurs later and sunrise earlier every day in March at the rate of two minutes a day. At the latitude of the Columbia River, our length of day will increase by one hour and 40 minutes this month. As if nature can't provide us with long days soon enough, we will take matters into our own hands, and change the hands of our clocks on March 8. On this date, at 2 a.m., daylight savings officially begins and we will advance our clocks one hour. Sunset will occur an hour later, but we won't really gain an additional hour of daylight, as the sun will also rise one hour later.
Venus leaves the eveningThe brilliant planet Venus has been keeping us company in the western evening sky for many months, but that is soon to change in spectacular fashion. This second planet from the sun passes between the Earth and our star on March 27 when it will come as close to Earth as it ever will. Watch it move closer to the horizon after sunset each evening until it disappears altogether and reappears in the morning sky.
Every eight years, Venus passes eight degrees north of the sun as seen from Earth. This optical alignment gives us a special treat. For two days before and two days after March 23, the planet will appear in both the evening and morning sky. Use binoculars just after sunset and before sunrise to observe this event.
At the same time, binoculars and small telescopes reveal that Venus exhibits a thin crescent phase just prior to disappearing altogether at inferior conjunction on March 27, and again when it reappears in the morning. When Galileo observed this 400 years ago, he concluded that the planets must orbit the sun and not the Earth.
Saturn to the frontThe giant ringed planet, like Venus, makes its closest approach to Earth in March this year, but because it is farther from the sun than Earth, it will appear opposite the sun in the sky. At opposition on March 8, and for the entire month, Saturn will rise in the east at sunset and remain in the sky all night. An observer on Saturn would have their own rare observation. They would see both Earth and Venus pass together from its evening sky into the morning sky.
To find Saturn, look to the east-southeast as darkness falls. The planet, the brightest star-like object in that part of the sky, lies near the rear foot of the constellation Leo the Lion.
The end of winterGroundhogs notwithstanding, it is Earth's axial tilt and orbit about the sun that determines the first day of spring. For six months, the tilt keeps the sun low in the sky, below the equator, and for six months, our northern hemisphere points to a sun riding high in the sky. At 4:44 a.m. PDT on March 20, the moment of the Vernal Equinox, the sun will cross the equator into the northern hemisphere and the lengths of day will grow longer than hours of darkness.
Earth's orbit changes our stellar view as well, as the constellations of winter slip into the west and the stars of spring appear in the east. By morning, the sky will fill with the wonders of the summer sky, a preview of evening skies to come.
Bob Duke is a local amateur astronomer, astronomy educator and weekly contributor to The Daily Astorian.