they are left over from the formation of stars and planets billions of years ago. before zipping around the sun with their characteristic big tails, comets that we see in our solar system start out as big chunks of rock and ice just floating around in something called the oort cloud. when the gravity from a large passing body, like a star, becomes strong enough, some large chunks of ice get pulled away from the cloud and head toward the sun. as that ball of ice gets close enough to the sun, its heat begins to melt some of the ice that makes up the comet. comets wallpaper. the melted ice becomes a gaseous tail that extends away from the source of the heat (in this case, the sun).
the tail is pushed out by the sun's solar wind. what keeps the comet in motion and guides its path is the gravity from all the planets and stars it passes. when a comet is in our solar system, most of the gravity affecting the comet's motion is due to the sun. comets wallpaper. as a comet gets closer to the sun it moves faster and faster, because the closer an object is to the sun the stronger the sun's gravity acts on it. as well as moving faster near the sun, the comet's tail will grow in length since more of the ice will be evaporating. comets are the largest objects in our solar system. they can measure up to ten miles across and have tails that can extend millions of miles into space. comets are often called “dirty snowballs” because the solid center of a comet, called a nucleus, contains rock particles trapped in frozen liquid. as a comet moves closer to the sun, the heat from the sun turns the outer ice into gas and the solid particles are released as dust. these gas and dust particles trail the comet in the form of a tail. comets wallpaper. sometimes two tails can be seen, a gas tail which is bluish in color, and a dust tail that looks yellowish. because the tail of a comet is always pushed away from the sun by solar winds, the tail can be either in front of the comets wallpaper or behind it.