Mercury, Venus, Mars, Jupiter, and Saturn, the five brightest planets, have been recognized since ancient times and may be viewed with the naked eye provided one knows when and where to look. They are visible for the most of the year, except for brief intervals when they are too close to the sun to be seen.
Jupiter is the largest planet and takes about 12 years to orbit the sun. It can only be seen with a large telescope or by projecting images onto a screen via a solar filter. The giant planet exhibits many features on Earth and in the other planets' atmospheres that help scientists understand how their environments work. It has four major moons: Io, Ganymede, Europa, and Callisto.
Io is the most volcanically active body in our solar system. It gets its name from the Italian word for fire because of the intense heat and gas emissions that pour into space from its interior. Scientists think that there is an ocean under the crust that is heated by friction between the inside of Jupiter and its surrounding gas and liquid clouds. This heating causes the ocean to melt, creating a sea that covers about one-fifth of the moon's surface.
Ganymede is the largest object in the Jovian system and one of the largest bodies in the Solar System. It has a diameter approximately 2.95 times that of Earth's and a mass about 18 percent more than that of Earth.
Mercury, Venus, Mars, Jupiter, and Saturn are the five brilliant planets in order of their distance from the sun. These planets do, in fact, shine brightly in our sky. They are frequently as luminous as, if not brighter than, the most brilliant stars. However, because these planets are so far away from Earth, their lights appear to be only dots of brightness in the night sky.
The nearest planet to Earth is Mercury, which orbits the sun once every 88 days. It is therefore called a "wandering" planet because it appears to move across the night sky from east to west relative to the other planets. Venus, Earth's sister planet, takes 225 days to orbit the sun; thus it can be found anywhere in the daytime sky provided that you know where to look. Mars, which takes 687 days to orbit the sun, can be found during certain times of the year when its orbit brings it within view of Earth. Jupiter, which takes 12 years to complete one orbit around the sun, can be found any time the moon is not present in the sky. Finally, Saturn, which takes 30 years to make one trip around the sun, can be found during certain seasons when it is visible after sunset.
All these planets are also very small stars in the night sky. From the vantage point of Earth, they appear as points of light with no detail visible.
By "bright planet," we mean any solar system planet that can be seen without a telescope and has been observed by our forefathers since time immemorial. However, as beautiful as they are, these planets don't always show up when you look up at the night sky because they are all within Earth's orbit (except for Jupiter which is about 584 million miles away). When they are on the other side of the sun, they are invisible to us.
However, if you know where to look, you will find these planets every night of the year. In fact, with a little help from your friends, you could see them anytime you want!
Jupiter is the largest and most massive planet in our solar system and as such, it dominates the view from earth when viewed from space. It is also the only planet that can be seen with the unaided eye under ordinary circumstances. However, like many other stars, Jupiter shows different phases during its monthly cycle of activity. When active, it produces strong winds, thunderstorms, and flare-ups of lightening. These events can be seen with the naked eye as a reddish coloration over much of the planet for several days at a time.
When not active, Jupiter appears faint red light in the night sky.
Which planets can be seen with the naked eye from Earth? For much of the year, Mercury, Venus, Mars, Jupiter, and Saturn are visible. Neptune and Uranus are not visible, and the eighth planet in our solar system is, of course, Earth. The Moon is also often visible from Earth and aids astronomers in studying these other objects.
The only major planet that cannot be seen with the unaided eye is Pluto. It is too far away from us now to be visible without a telescope, but it was once possible to see it with the naked eye from certain locations on Earth. A solar eclipse will sometimes show you something else hidden from common view: a moon or planet orbiting directly between Earth and the Sun. These bodies are called interplanetary because they lie between Earth and the Sun. They include the four terrestrial planets (Earth, Mars, Venus, and Jupiter) as well as the five giant planets of the Solar System (Saturn, Uranus, Neptune, Pluto, and Ceres).
Ceres is the largest object in this class of body, but it cannot be seen with the unaided eye. It is too small and too far away from us to be detectable with the human eye. It takes a large telescope to see it.
Pluto used to be a part of our solar system, but it is now considered a dwarf planet.
Without a telescope, there are five planets visible: Mercury, Venus, Mars, Jupiter, and Saturn (six if you include Uranus for those with keen eyes!). All of them, with the exception of Neptune, travel within 7 degrees of the ecliptic. That is the plane in which Earth orbits around the Sun. So, they all appear to move across the sky from west to east.
Jupiter is the largest planet and also the most distant one from the Sun. It can be seen with the naked eye on a clear night when it is rising or setting. However, it is not easy to see because it is so bright, it keeps outshining everything else even at its closest approach to the Earth when it is below the horizon.
The best time to look at Jupiter is when it is high in the sky during the evening. It's very bright orange-yellow color comes from many clouds composed of water droplets containing ammonia which reflect light from the sun back into our eyes. As we watch it set over the horizon, it will gradually fade from view until it is completely dark outside.
In order to see Jupiter with the naked eye, you need a clear night with no clouds or light pollution. Its color makes it obvious when you have found it in the sky; just look for a big bright object moving across the face of the moon!