AstroBob and the Grand Pageant of Planets

Amateur astronomer Bob Fisher (better known as AstroBob around these parts–much to his chagrin) has been a passionate star-gazer since childhood when he first saw the superbly dark skies of the Adirondacks on camping trips.  A part-time resident of Olmstedville since 1991, he taught earth science and astronomy in New York City public high schools for more than two decades before making his permanent home here in 2006.  Now a substitute teacher in Warren and Essex county schools, he is also an active astrophotographer. He frequently leads astronomy workshops in local schools and libraries, and occasionally serves as a docent at the American Museum of Natural History in New York City.

Ever since the dawn of humanity, the magisterial movements of the Sun, Moon, planets and stars have been an endless source of wonder and instruction. It’s a sobering thought in this age of atomic clocks, cell phones and GPS that prior to the 18th century the most accurate way of telling time was done by observing the position of the Sun, Moon and stars. Ancient observers noticed that from dusk to dawn, the stars moved across the sky with predictable regularity. Over time, they observed that some of these bright stars shone with a steady light (did not twinkle), and mysteriously kept changing their position relative to the surrounding stars. This difference in their movements eventually earned them the name planets (Greek: planasthai – to wander). The birth of astronomy can be traced to the first great civilizations in      Babylon, China, and Central/South America, where sky watchers in all these diverse places kept careful, accurate records of planetary positions for months and years at a time. They eventually noticed that a regularity occurred enabling them to predict precisely where each planet would be in the sky well into the future.

For the casual, modern observer who rarely has the time to watch the sky, here is the key to know where to look: The planets always follow the path (called the ecliptic) of the Sun. In mid-March this path is due east to west. A planet will rise due east, be highest in the sky when it is directly above the southern horizon and will set due west.  Early March will provide us the best opportunity this year to see all five of the  planets visible without a telescope, where each one will reveal its unique personality. Let’s begin our planet tour on during the first week of March:

MERCURY

Go outside at dusk (6:15P.M) and face an unobstructed west, look for the place where the sun set and @ 15 degrees directly above that spot look for a “star” hiding in the bright glare.

Mercury over New Jersey, 6:30pm on March 5, 2012 Photo by Bob Fisher

VENUS

Moving higher up along the ecliptic in the west, we come to Venus. Shining like a brilliant jewel, it is unmistakable. Although it will reach greatest brilliance in mid-April, she is the third brightest natural object in the sky after the Moon and Sun. Since Venus is inside the Earth’s orbit, it goes through phases like our Moon. If you have a modest telescope, you will notice the planet will look like a small first quarter Moon. Later this month, it will appear larger and brighter, unmistakably displaying a thin crescent. At the Equinox, (3/20/12) when the Moon is nearly new, try this fun experiment to see your shadow cast by Venus’s light. You must be in a very dark place and having snow on the ground would enhance the shadow. Although the ancients named Venus after the goddess of love, a visit there would be far from lovely. The terrain is a desert baking at 800+ degrees F, with a thick permanent carbon dioxide atmosphere and occasional rain of sulfuric acid.  No romantic garden of sensual pleasure. Blame modern science for revealing her true nature!

JUPITER

By today’s standards, the telescope Galileo used in 1610 was probably not as good as a piece of junk    purchased from a big box store at the mall. But his crude instrument, careful observations, meticulous diagrams and notes enabled him not only to make profound astronomical discoveries but also start his troubles with the church and eventual trial and inquisition. Why all the fuss? Over a series of nights, he noticed that the planet Jupiter had four faint stars that always remained in a straight line but constantly changed position. He correctly concluded that they must be moons orbiting the planet. Since the Catholic Church believed that the Earth was the center of the universe, and the stars, Sun, Moon and planets revolved around the Earth, it was heresy to claim that any celestial objects revolved around anything else. This week you can observe these four Jovian satellites as they constantly change position within a period of a few hours. All you need is a good pair of binoculars. With a small telescope at 50x, it is possible to see the dark and light bands of gas clouds covering the largest planet in our Solar System. In our sky it is readily visible just above Venus and this week both objects make a striking pair! Jupiter is getting closer to the Sun and will be lost in daylight by late Spring.

Photo by earthsky.org

INTERLUDE: By 7:30, Mercury will have set and the Moon will be high in the South. Mars is low in the South, but to get the best view of our last two planets we will have to wait a few hours. Take a break, and come back out at 11:00 or later.

MARS

Mars, named after the Greek god of war because of its blood red color has a rich cultural and scientific history. Like the deserts of the Southwest, the color is derived from iron oxide (rust) in the soil. This March will be the best time to observe Mars, when it reaches opposition (closest approach), to Earth on March 3rd. This is the best time to see some surface details in a modest (4inch – 10inch) telescope. Under high magnification and stable seeing conditions, you should see dark markings and the shrinking South Polar Ice Cap which should appear as a small bright white spot. The larger the telescope, the clearer the image. Mars will surely be back in the news this August, when the sophisticated new rover lands  (hopefully intact) on August 6th .

SATURN

Most people who look at Saturn through a telescope for the first time are dazzled by the other-worldly beauty of this planet as the beautiful rings surround the planet giving it a three dimensional effect. After 11:00 P.M., it rises higher and higher and should be a great object to see all Spring/Summer long.

NOTE: Although I gave details for observing during the first week of March, the first two weeks will be the best time for planet viewing. The main difference after March 15th will be that Mercury will disappear from view as it gets lost in the glare of the Sun and Jupiter will be well below Venus. I hope you have the opportunity to see these magnificent planets this week!

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