Observing the planetary movements with the naked eye may teach you a lot (i.e., no telescope). Without a telescope, there are five planets visible: Mercury, Venus, Mars, Jupiter, and Saturn (six if you include Uranus for those with keen eyes!).
With a little help from your telescope, you'll be able to see more than just these five planets. In fact, viewing the planets with a telescope allows you to study their surfaces in greater detail than is possible with the unaided eye.
People have been looking at the night sky with telescopes for many centuries now. Modern astronomers use telescopes to study objects on other parts of the solar system, including stars and galaxies. They also use telescopes to look into deep space and explore how other worlds might fit inside their planet's orbit.
For people who live near enough to see the moon or sun with the naked eye, it's easy to forget that they're actually very small and distant objects. But because telescopes make such large images, even people who cannot see very well should be able to observe some of the finer details of these bodies. The telescope also reveals information about the distance between us and other objects in the sky not readily apparent with the naked eye.
The telescope has many other uses too. Scientists have used them to take pictures of faraway exploding stars, alien worlds, and more.
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 brightest planet and can be seen with the unaided eye under certain conditions. It appears as a white light that moves slowly across the night sky from west to east. The farther away it is, the more its yellowish color becomes apparent.
In fact, Jupiter is so bright that it often obscures other stars! You need a telescope to see other stars beyond Jupiter.
Jupiter is also very large in comparison to our own tiny planet. It is over 93 million miles in diameter -- about half again as big as Earth. That's larger than anything else in the Solar System except maybe for Saturn.
Jupiter has at least seven moons. They were first discovered by Galileo Galilei in 1610. Today, their names are given in alphabetical order: Adrastea, Amalthea, Ananke, Anthe, Axum, Calypso, and Circe.
Mercury, Venus, Mars, Jupiter, and Saturn are the only planets visible from Earth with the naked eye. The other two, Neptune and Uranus, need the use of a small telescope.
Venus shines brightly in the night sky, while Mercury is barely visible even with the aid of binoculars or a small telescope. Mars is the brightest object in the Martian sky and can be seen with the naked eye on a clear night when it crosses between Earth and the moon. Jupitor and Saturn also can be seen with the naked eye, but they are not as bright as Mars.
Neptune was originally discovered by Galileo Galilei in 1613 and has been seen by many others since then. It takes more than 500 years to orbit the sun so this distant planet will not be visible again for another 500 years at its current position beyond Pluto. Uranus was first spotted by William Herschel in 1789. Like Neptune it takes about 5 hours to complete an orbit, so it too will not be visible for several hundred years.
Planets were originally identified by astronomers by how much they moved against the stars. Modern astronomy uses telescopes to observe objects outside the solar system including galaxies, star clusters, and planetary systems.
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 Sun also becomes a star-like object from time to time, such as when it crosses the center of the Milky Way Galaxy. These events are called Solar Eclipses.
Earth's atmosphere allows us to see far away into space, but only under certain conditions. Light from distant objects such as stars or galaxies reaches all the way to the earth if: 1 It passes through an air mass that is clear of clouds or other particles that would block its path; 2 Its direction is almost straight up or down; 3 Its light does not get absorbed by chemicals in the lower levels of the atmosphere (such as water vapor or ozone); and 4 Its intensity is sufficient to produce a sharp image on a sensitive camera sensor. When these conditions are met, we say that "the moon is out."
From mid-August to late October, the Moon is always visible in the night sky because it is one of the planets that can be seen with the unaided eye. Beyond this time, it is no longer visible because then it enters the constellation Cancer (the Crab). But it will again become visible in the springtime sky around March 20th.