Fig. 51: The giant planet, Jupiter. The four largest moons can be observed in a different position every night.
Fig. 52: Saturn has the most extensive ring struc- ture in our Solar System.
Fig. 53: The Pleiades is one of the most beautiful open clusters.
Planets
Planets change positions in the sky as they orbit around the Sun. To locate the plan- ets on a given day or month, consult a monthly astronomy magazine, such as Sky and Telescope or Astronomy. You can also consult Autostar for information about planets. Scroll to the "Object: Solar System" menu and scroll through the lists of plan- ets. When a planet you are interested in displays, press ENTER. Use the Scroll keys to display information about the planet, such as the planet's coordinates, and the rise and set times (Tip: enter a date in the Date menu and you can determine if a plan- et(s) will be visible during the night of the entered date by checking its rise and set times). Listed below are the best planets for viewing through the
Venus is about
Mars is about half the diameter of Earth, and appears through the telescope as a tiny
Jupiter is the largest planet in our solar system and is eleven times the diameter of Earth. The planet appears as a disk with dark lines stretching across the surface (Fig. 51). These lines are cloud bands in the atmosphere. Four of Jupiter’s moons (Io, Europa, Ganymede, and Callisto) can be seen as
Saturn is nine times the diameter of Earth and appears as a small, round disk with rings extending out from either side (Fig. 52). In 1610, Galileo, the first person to observe Saturn through a telescope, did not understand that what he was seeing were rings. Instead, he believed that Saturn had “ears.” Saturn’s rings are composed of billions of ice particles ranging in size from a speck of dust to the size of a house.
The major division in Saturn's rings, called the Cassini Division, is occasionally visi- ble through the
Deep-Sky Objects
Star charts can be used to locate constellations, individual stars and
Stars are large gaseous objects that are
Nebulae are vast interstellar clouds of gas and dust where stars are formed. Most impressive of these is the Great Nebula in Orion (M42), a diffuse nebula that appears as a faint wispy gray cloud. M42 is 1600 light years from Earth.
Open Clusters are loose groupings of young stars, all recently formed from the same diffuse nebula. The Pleiades is an open cluster 410 light years away (Fig. 53). Through the
Constellations are large, imaginary patterns of stars believed by ancient civilizations to be the celestial equivalent of objects, animals, people, or gods. These patterns are too large to be seen through a telescope. To learn the constellations, start with an easy grouping of stars, such as the Big Dipper in Ursa Major. Then, use a star chart to explore across the sky.
Galaxies are large assemblies of stars, nebulae, and star clusters that are bound by gravity. The most common shape is spiral (such as our own Milky Way), but galaxies can also be elliptical, or even irregular blobs. The Andromeda Galaxy (M31) is the closest
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