About our Planets, Part Two: Beyond the Asteroid Belt:Author: Jeff Seward
In the previous article, we tackled the planets nearest the sun, and which could easily be seen in the night sky.
From Mercury to the asteroid belt, our nearest neighbors appear almost like stars, and can make star gazing a fascinating activity for both young and old alike. Beyond the asteroid belt are cold, massive planets, with their own gases and storms, and their own stories to tell. If you are interested in viewing these planets in the night sky, you may need more powerful tools for your home astronomy session, which will include the following.
Because the planets and dwarf planets beyond the asteroid belt are much farther away, you won't be able to see them using a pair of binoculars, much less with your naked eye. You will need a home telescope, preferably one with very good resolution, as some of the planets have interesting properties.
You may also need star maps, since some of the outer planets are described in reference to nearby constellations. The darker your surroundings, the easier it will be to view the outer planets. You will need a dim flashlight so you can better read your star maps and keep light from disturbing or disrupting your viewing. The properties of planets are important when considering the outer planets, as some of them are now described as dwarf planets because they did not meet one or more qualifications to be planets. According to internationally approved definitions, a planet must be a spherical body orbiting the sun, with its shape brought about by its own gravitational forces. A planet should also clear the neighborhood surrounding its orbit.
The first planet beyond the asteroid belt is the gas giant Jupiter, home to sixty three satellites. The largest of all the planets, Jupiter is equal in volume to over one thousand three hundred earths, and in mass to over three hundred earths. This massive planet's atmosphere is made up of hydrogen and helium, and is home to storms aplenty. Jupiter has long been an object of fascination to the ancients, and was named by the Romans after the king of their gods. Along with Saturn, Uranus, and Neptune, Jupiter is part of the Jovian planets, a group of gas giants. Because of its atmosphere, Jupiter assumes a red to orange appearance when viewed with a telescope. A Great Red Spot, a giant storm that has existed for hundreds of years, rests on Jupiter's surface; around Jupiter is a faint ring of satellites. Jupiter is the brightest body in the sky, next to Venus, although Mars overtakes it in brightness at certain times of the year.
Not only is Jupiter bright, but its massive size influences the size, position, and behavior of the solar system. In fact, Jupiter gives off more heat than it receives from the sun. Jupiter is also the fastest rotating planet, creating a bulge at its equator that you can see through your telescope. Saturn is the next gas giant, and could well be the most famous, most colorful planet in the solar system. Saturn has thick rings of ice particles that you can easily see through your telescope, and is also home to fifty six satellites. The whole planet, however, is less dense than water, and, like Jupiter, has an atmosphere composed primarily of hydrogen and helium. Like Jupiter, Saturn is a very hot planet, and gives off more energy into space than what it gets from the sun. Saturn's ring system, however, often blocks its colors. Now, Saturn is colored bright blue, like Uranus, due to colder temperatures on the planet. You can still see Saturn's rings, however, using your telescope. With a more powerful telescope, you may also see Saturn's most famous moon, Titan, which is the only satellite in the solar system with a thick atmosphere.
The ancients have long observed and tracked Saturn, along with the only other planets in the solar system visible to the naked eye from earth: Mercury, Venus, Mars, and Jupiter. To the naked eye, Saturn is a bright, slightly yellow star. Uranus, the third gas giant, holds twenty seven satellites in orbit, and was the first planet discovered using a telescope. Mistakenly identified as a star, Uranus has a faint ring system, is colored light blue, and has moons named after characters from Shakespeare's and Alexander Pope's works. To the naked eye, Uranus appears like a faint star; with a telescope, Uranus is a pale blue disk, and its two largest moons, Titania and Oberon, might be visible. Neptune is the last planet of the solar system and is home to thirteen moons. With a telescope, Neptune can be seen as a brilliant blue-green planet, a property that can be described as being due to the traces of methane in the planet's atmosphere. Like the other gas giants, Neptune has a ring system.
It was also the first planet to be discovered due to mathematical predictions, and not due to observations of the sky. Beyond Neptune are two dwarf planets, Pluto and Eris. Pluto, made of rock and ice, is home to three satellites, and was once considered a planet. Eris, on the other hand, is the largest dwarf planet in the solar system, and is home to at least one moon. Star gazing and planet watching are enjoyable activities that anyone can enjoy. With the right tools and knowledge, you can locate the planets and have a great time with your family.