Craig C. Freudenrich
Look in the sky any time of the year, day or night, and you'll see an object from our solar system. The most obvious daytime object is the sun, the shining star at the center of the solar system. Depending on the time of month, you may see the moon during the day. If not, you will most certainly see it at night and notice that the phases of the moon change from day to day during the month. With your naked eye, you also can spot the moon's bright areas and dark "seas," perhaps even a crater or two. The sun and moon are the brightest objects in our solar system, however. The others can only be observed at night and often require binoculars or a telescope for viewing.
When you scan across the night sky, you'll notice that certain objects don't twinkle and change position over the course of the year. These are the planets. They include the rocky inner planets (Mercury, Venus, Mars -- and our Earth) and the outer gas giants (Jupiter, Saturn, Uranus and Neptune). You can see the planets with the naked eye, but only a telescope can provide details. Using a modest four-inch aperture telescope, you can see the gaseous bands of Jupiter and the rings of Saturn.
Turning such a telescope toward Jupiter should show four moons (although there are many more that you cannot see). Like our moon, Jupiter's moons orbit the planet and change position from one night to another. It is more difficult, if not impossible, to see the moons of Saturn, Uranus and Neptune with a small telescope.
Occasionally, you may see a comet pass near the earth. Comets are made of ice and dust. They come from a region called the Oort cloud at the far edges of the solar system. As they approach the Sun and warm up, they shed gases in a long tail that you can see. When the Earth's orbit crosses the orbit of a comet, the dust and debris hit the atmosphere and make a meteor shower such as the Perseids each August. Often during the night, you can see several random meteors or "shooting stars."
Besides comets and meteors, nighttime observers might spot rocky bodies that orbit between Mars and Jupiter called asteroids. Doing so requires a telescope and several nights of patient observation. The brightness of asteroids may change as they rotate.
A larger aperture telescope can bring Pluto, now classified as a dwarf planet, and similarly sized Kuiper Belt objects into view. They orbit the Sun much farther out than the planets orbit. It takes several nights of observation to see them move.
The sun and nine planets of our system orbiting. (iStockphoto/Baris Simsek)
When we gaze into the night sky, we rarely see more than the stars and the moon (or sun during the day). Most of our solar system can't be seen by the naked eye and, in fact, much of what exists in our solar system has yet to be discovered. Nevertheless, it is known that our solar system is made up of more than just planets. In addition to the sun and the planets in orbit around it, our solar system also includes numerous moons (several planets have one or more moons, and some moons also have moons) and a range of supernova explosions, asteroids, comets, meteors and a lot of space dust.
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