Image source: PBS Learning
The Moving Sun
This week our planet reaches the three-quarters mark on its annual trek around the Sun. September 22 is the first day of autumn and we will be experiencing nearly equal amounts of daylight and darkness on our world. A breath of autumn has been in the air this past week even though the heat grew throughout the day, the intensity of shadows seemed a bit less to me and the sunlight less merciless. On mornings when the view of the sun's crepuscular rays extending from the darker Gulf-formed clouds in the east is a lovely sight I never tire of seeing and the red-orange globe of the Sun rising through those clouds is always thrilling — at least it was to me.
These days I am driving westward at sunset, so I can enjoy the view of the sun's motion along the horizon to reach due west as autumn arrives. If you live on South Padre Island or Port Isabel, you probably fully take advantage of observing this motion against a flat horizon of the blue waters and golden dunes rather than the expressway overpass. The equinoxes are that point in time when the Sun rises and sets at the crossing point of two imaginary lines in space, Earth's equator extended outward, and the ecliptic. The angle created by this intersection is 23.5 degrees, the amount of the earth's tilt off from a pole-to-pole vertical 90 degree angle. Geometry makes the seasons; more math magic for those of us who wondered why we had to learn that in high school or middle school math classes.
Ask your favorite math teacher to show you how that fits into astronomy; it might intrigue you enough that you actually want to study on your own. To begin a family science fair project, make a sketch of the horizon from your home and some fixed object, such as a light pole or a palm tree along the horizon, and mark where you see the Sun rise and/or set along the horizon. Keep collecting data for a few months and then analyze the information and share what you learn.
Horizon-based astronomy was extremely prevalent among the people living in this hemisphere in ancient times. Their observatories still mark the motion of the Sun as well as particular stars and planets along the horizon. Researching Chaco Canyon and Pueblo Bonito in the Southwest, the western Medicine Wheels, and the Aztec and Mayan temple ruins of South and Central America and Mexico could be quite a fascinating family adventure. I think that could be the ‘plus’at the September night hike at Resaca De La Palma for September.
Expect the summer constellations to be visible in the sky until late evening, even though it will technically become autumn on Monday. The reddish glow of Antares in the Scorpion will slowly move westward, followed by the Teapot asterism, while the Great Square of Pegasus will be nearing the zenith and delighting baseball fans with a view of the baseball diamond in the sky.
Once you locate the square, let your vision drift northward to the W of Queen Cassiopeia, and then stray upward to the crooked little house of her husband, King Cepheus. Drifting off first base is a wispy drift of stars in a V shape on its side, open end towards Cassiopeia. This is Andromeda, the daughter of the king and queen.
While you are watching the rotation of the royal family, watch the Baseball Diamond and Andromeda drift towards the zenith and on towards the western throughout the season.
The South Texas Astronomical Society is planning an event for the official Observe the Moon night October 4 during World Space Week. If you have any interest in the science part of this, you might want to encourage your favorite student to think of some astronomy-based science fair project that might be aided by participating in this event. I know the Brownsville ISD will hold its elementary science fair in the fall, but I am not sure about other RGV schools.
Until next week, DO let some stars get in YOUR eyes.
