Thursday, March 13, 2014
The Ellensburg sky for the week of 3/15/14
Saturday: Has there ever been life on Mars? Astronomers don’t know. But the Mars Curiosity Rover has been digging up some strong evidence that Mars was hospitable to life in the past. At the end of 2012, the first drilling assignment for Curiosity found clay-like minerals that form in the presence of water. This past December, scientists announced the strongest evidence yet for an ancient fresh-water lake in Gale Crater. Planetary geologist John Grotzinger said that Earth microbes could have thrived in this lake if they were placed there. For more information, go to http://goo.gl/7E6MD8. Mars is about one fist held upright and at arm’s length above the east-southeast horizon at 11 p.m. The bright star Spica is just to the right of Mars.
Sunday: While we may refer to the moon tonight by the boring title, “a full moon in March”, Native Americans in the eastern United States called this moon the Full Worm Moon. By March, the temperature has increased enough so the ground starts to thaw and earthworms make their first appearance. Earthworms attract birds. Northern tribes thought of the bird connection when they referred to the March full moon as the Full Crow Moon. Tribes in parts of the country with maple trees call this full moon the Full Sap Moon. For more full moon names, go to http://www.farmersalmanac.com/full-moon-names.
Monday: Ask someone which day in March has the same duration day and night. Go ahead, ask someone. Why are you still reading this? I can wait. If that person said the first day of spring, they are wrong. Today, three days before the first day of spring, is the date in which day and night are closest in duration. There are two main reasons for this. First, the atmosphere acts like a lens, bending light from the Sun above the horizon when the Sun is actually below the horizon. This makes the Sun appear to rise before it actually rises and appear to set after is actually sets. Second, spring starts when the center of the Sun passes through the point called the vernal equinox. But, the Sun is not a point. The upper edge of the Sun rises about a minute before the center of the Sun and the lower edge sets a minute after the center of the Sun. Thus, even if we didn’t have an atmosphere that bends the sunlight, daytime on the first day of spring would still be longer than 12 hours.
Tuesday: Venus is one fist above the southeast horizon at 6:30 a.m.
Wednesday: Jupiter is six and a half fists above due south at 8 p.m.
Thursday: Look up in the sky. It’s a plane. It’s a bird. No, it’s the vernal equinox. The vernal equinox!? Spring starts at 9:57 a.m. Pacific Daylight Time. The first day of spring is often called the vernal equinox. This label for the day is misleading. The vernal equinox is actually the point in the sky where the Sun’s apparent path with respect to the background stars (called the ecliptic) crosses the line that divides the stars into north and south (called the celestial equator). This point is in the constellation Pisces the fishes. At the vernal equinox, the Sun is moving from the southern region of background stars to the northern region. Since the Sun crosses the vernal equinox at night, tomorrow will actually be the first full day of spring.
Because the Earth slowly wobbles like a spinning top, the vernal equinox is slowly moving into the constellation Aquarius. By the year 2597, the vernal equinox will reach the constellation Aquarius and the “Age of Aquarius” will begin. Until then, we’ll be in “the age of Pisces”.
Friday: The moon is near Saturn late last night into early morning. By the time both have risen at 1 a.m., Saturn is less than half a fist above the moon. By 6 a.m., they have moved to the southern sky and are a little bit farther apart.
The positional information in this column about stars and planets is typically accurate for the entire week. For up to date information about the night sky, go to https://nightsky.jpl.nasa.gov/planner.cfm.