StarWatch: Moravian College Astronomy

StarWatch for the greater Lehigh Valley

FEBRUARY 2012

FEBRUARY STAR MAP | STARWATCH INDEX | MOON PHASE CALENDAR

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807 FEBRUARY 5, 2012: Moon, Planets Reveal More: Perhaps you have been noticing that dazzling bright star in the SW after sundown. Alas, it is the planet Venus. There is no brighter “star” in the heavens. Above Venus and to the left is Jupiter, the ruler of the solar system, but not quite as bright. Saturn and Mars come along later in the evening, although Mars is rising about 8 p.m. What’s nice about the planets, from Mercury to Saturn, and the moon, is that they are bright and can reveal other interesting celestial gems as they wander among the stars. On Monday, February 6, a bright waxing gibbous moon is 5.5 degrees to the SSW of the Beehive, an old open cluster of stars in Cancer the Crab. Binoculars will be needed to view this swarm of luminaries that have been around for some 600 million years and might well be related to another more famous open cluster, the Hyades, which is represented by the “V” of Taurus the Bull minus its brightest star, Aldebaran. Likewise on Thursday the 9th, a full moon visits Mars. Moonrise is about 8 p.m., but give the moon and Mars a few hours to gain altitude, and the experience will be more productive. The moon will be about two fists held at arm’s length (thumb on top) above the horizon by 10 p.m. A bright warm-colored star will be about one fist’s distance to the moon’s left, and that will be Mars. The sneakiest rendezvous this week, however, will also occur on Thursday evening right after it gets dark. Look at Venus using binoculars in the WSW about 45 minutes to an hour after sundown. To Venus’ left and very close to the Goddess of Love, less than half a lunar diameter away, will be a much fainter starlike object, also a planet. You’ll be looking at Uranus. Any small to mid-sized telescope will also reveal the two objects in the same field of view. The day before and after are still good views through binoculars, but with wider separations. Much success!

808 FEBRUARY 12, 2012: Promise Her the Stars and Deliver: This is my favorite time of the winter. Yesterday (Monday, Feb. 6) was one of the clearest days that I can remember in recent history. The afternoon temperature popped into the mid-fifties, and I almost thought that I heard the tulip bulbs pushing through the warm, moist soil of my garden. Yes, spring was truly in the air, and I can say that it brought great joy to my heart. Yet at sundown, as I was assembling my astronomical gear at the edge of a local farmer’s field to photograph Venus bathed in a moonlit landscape, the sky darkened to reveal the winter constellations. The fact that these familiar star patterns, such as Orion the Hunter, Taurus the Bull, Canis Major/Minor the Big Dog/Little Dog, Gemini the Twins, and Auriga the Charioteer were still to the east of south, the rising side of their journey across the sky, told me that at least astronomically, winter was far from over. This week, the moon rises later in the evening so it does not disrupt the splendor of these great wintertime figures. If you and your sweetheart are outside at 8 p.m. on Valentine’s Day, Alnilam, the center star in the belt of Orion, will literally be due south. That for me is the focal point of the astronomical winter. Use the belt to slide downward to the coolest dog in the sky, Canis Major, which boasts the brightest star of the night, Sirius. Above and to the left of Sirius is Procyon, the alpha star of Canis Minor, and above it are the twin stars of Gemini, Castor and Pollux. Pollux is the brighter of the pair. Near the zenith, and well above Orion, will be Auriga’s Capella, the fourth brightest star of the night. Down and right from Capella is Aldebaran, the brightest star of the small V-shaped head of the shaggy bull, Taurus. Following Orion’s belt upwards leads you back to Aldebaran as a check. A kiss from your sweetheart is in order. After all, you’ve just given her the stars. The moon and sun come along later.

809 FEBRUARY 19, 2012: Easter will Always Occur in the Spring: The Lenten season begins on February 22, starting with Ash Wednesday, commemorating the 40 days that Christ spent fasting in the desert prior to the beginning of his ministry on Earth. Those 40 days do not include Easter Sunday nor the intervening Sundays before Easter, so Lent in 2012 contains 46 days prior to Christ’s resurrection. The tradition of restricting the consumption of certain foods or giving up certain luxuries during Lent is in acknowledgment of the hardships that Christ endured during this period. Shrove Tuesday, the day before Lent, is considered the time when penitents “shrove” or “shrived,” acknowledged their sins to ensure God’s forgiveness and free themselves from guilt. Shrove Tuesday is also called Fat Tuesday from the French (Mardi-Tuesday and gras-fat) when oils and fats, considered luxuries, were consumed prior to the beginning of Lenten fasting. For the English, fatty pancake recipes were favored thus leading to their consumption on that day and Shrove Tuesday to be also known as Pancake Tuesday. Pennsylvania Germans cooked greasy donuts instead, a tradition that I remember so fondly in my grandmother Becker’s yummy square-shaped Fastnacht treats which she continued to make through age 100. In order to keep Easter and other seasonal holidays reoccurring at their respective times of the year, it is essential to maintain a calendar that is in step with the seasons. Although the actual formula for calculating Easter is more complex, a generic variant is to say that Easter occurs on the first Sunday (April 8) after the first full moon (April 6) after the Vernal Equinox (March 20). The period of time between the sun’s two successive crossings of the Vernal Equinox, the position in the sky where the sun’s location is directly over the equator, marks “the beat” of a Tropical year. That beat, however, is actually 20 minutes shorter than the Earth’s revolution period around the sun with respect to a fixed reference, the manner in which orbital periods of other celestial bodies are normally measured. This means that the location of the Vernal Equinox in the sky changes from year to year, sliding westward among the stars, a direct result of the Earth’s axis wobbling (precessing) like a huge top over nearly a 26,000 year cycle. Using the sun’s crossing of the vernal equinox to regulate the yearly beat ensures that holidays like Easter and Christmas, July 4th, and Labor Day take place during their respective seasons. Six thousand years from now, in 8012 AD, Easter will happen with the winter constellations fully dominating the evening sky, but springtime will still be in the air. Considering global warming, it may even feel like summer. Happy Easter to all!

810 FEBRUARY 26, 2012: Leap Year Day: When I was in elementary school, probably in the fifth grade, there was a girl in class whose sister had been born on February 29, 1952. We were perplexed because in 1960 this was only the second time her birthday fell on February 29. What happened to people that were born on leap year day we thought? Did they live for an especially long period of time or did they just celebrate their birthdays on a different date? The girl’s sister was similar to any third grader, so we concluded that she probably celebrated her birthday on either February 28 or March 1. Such were the musings of 10 year old kids. There is nothing tricky about leap year. The Earth has a job to perform—orbit the sun with respect to a slowly moving point in the sky called the Vernal Equinox. This is called the tropical year. It takes an average of 365.2422 days for the Earth to complete this task. The “job” of the Gregorian calendar, created in 1582, was “to beat” as closely as possible to the tropical year cycle. A Gregorian year has 365.2425 days. Since calendars must have a whole number of days, each year the Earth falls approximately one quarter day behind in its solar orbital cycle. After four years the Earth is about one day in arrears of its solar schedule, and we give Earth an extra day to catch up—leap year day. Years divisible by four without a remainder are designated as leap years. However, this assumes that the Earth orbits the sun in 365.2500 days, the exact fault of the Julian calendar and why it was replaced. To correct for this excess, the Gregorian calendar added that only century years wholly divisible by 400 were leap years. Since its inception, only the century years of 1600 and 2000 have met this leap year criterion, but the story is still not concluded. Finally, to bring the Gregorian calendar into closer agreement with the tropical year, modern astronomers have decreed that the century years of 4000 and 8000 will not contain leap years.

[February Star Map]

[February Moon Phase Calendar]