Stargazing: Planets do a square dance
Gatehouse News Service
The parade of planets has intrigued star-watchers for thousands of years.
Here is a group of what look like bright stars - minus any obvious twinkle - which unlike the rest of the starry dome, they keep changing position.
Referred to as “wandering stars,” they were seen to loop around the sun and Earth from our perspective, and it took many centuries to untangle just what they were seeing - what went around what?
Debates about a flat Earth were coupled with the heretical notion that the Earth may be one of those “wandering stars.”
Careful watch of the planets in their orbits also shows an unusual dance. Just when you thought they all were heading one way across the sky, west to east as seen night to night - each outer planet (beginning with Mars) periodically will make a U-turn and head back for a while only to reverse again and resume its eastward trek!
Leave it to astronomers to find a technical word for their dosie-do: retrograde motion.
This loop effect is an illusion, caused by changing perspective as the Earth in its faster orbit, overtakes the outer planet; as we pass it by it seems to temporarily recede away.
The inner planets, Venus and Mercury, don’t make this dance but as seen from either of them, Earth is doing the same thing as they pass us by in the cosmic dust.
In mid-February, Mars may be seen rising in the east at around 8 p.m.
You can have a much better view later in the evening. Like a strikingly bright red star of magnitude -0.7, the planet has doubled in brightness in the past month and will double in brightness again as it approaches its closest approach on March 3, 2012.
It will be going through its retrograde loop in February, seemingly going backwards and allowing it to quicken its time of rising.
Look west for brilliant Venus in evening twilight, and bright Jupiter to the upper left.
They are about 30 degrees apart in mid-February, with the gap between them narrowing by about a degree a day.
Mercury is currently out of sight, in conjunction with the sun. Saturn rises in the east at around 11 p.m. and is at its highest in the south before dawn.
Of course there are more planets, all unknown to the ancients. Uranus, can be found in binoculars currently not far from Venus, if you have a proper chart.
Neptune is fainter still and is lost in twilight. Former planet Pluto (it’s supposed to be called a “dwarf planet” now) requires a large telescope (10” aperture or more), a very dark night and a detailed chart.
Did you know there was once another planet listed in the solar system, closer to the sun than Mercury?
It was called Vulcan by astronomers in the mid-19th century, who had fleeting glimpses of what they suspected was a planet.
Vulcan was never confirmed, unless you are a true “Trekkie” and include the fictional TV show abode of our beloved Mr. Spock.
Johannes Kepler (1571-1630), a German astronomer, developed three famous laws of planetary motion that helped to lay the foundation of modern astronomical research and our understanding of the solar system.
He utilized the remarkably accurate data of Danish observer Tycho Brahe, who before the invention of the telescope, charted the positions of the stars against which the planets are seen to move.
Kepler’s work became a template about which Isaac Newton formed his theory of gravitation. His studies helped prove that all the planets, including Earth, revolve around the sun.
The basics of the three laws are, 1. Each planet orbits the sun in an ellipse, of which the sun is at one focus; 2. The line between a planet and the sun sweeps out equal areas at equal times, and thus a planet moves faster when closer to the sun; and 3. The square of the time taken by a planet to orbit the sun is proportional to the cube of its mean distance from the sun.
Kepler and Tycho both have been memorialized with prominent lunar craters named for them.
All this information and much more is available in your public library, as well as online.
Even if you cannot easily get out in the cold night to see the stars, reading is a wonderful alternative.
Kepler in fact, had poor eyesight and made few actual astronomical observations, but with his mind, pen and paper, he moved worlds.
Keep looking up!