What makes comet glow

Its gravitational pull is so slight that you could leap off its surface into space—another reason not to visit! Another probe actually collided with a comet in They were thought to symbolize times of disaster and doom. All rights reserved. Personality Quizzes. Funny Fill-In. Amazing Animals. Weird But True! Party Animals. Try This! Explore More.

A coma is the fuzzy-looking glow that can be seen around the head of a comet. Fast Facts. Please be respectful of copyright. The nucleus of even a huge comet is only a few dozen km across, so at that great distance is just a tiny dot. Anthony has details on his observations on his McNaught page.

The comet looks huge -- and the fuzzy part can be bigger than planets! Far from the Sun that gas is frozen, and the comet is solid. But heat it up, and that ice turns into a gas, creating the comet's coma Latin for hair. In that gas methane, water, ammonia, and lots of other things, many of which are pretty nasty. But why is it green? Ah, that's a good question I'm glad I asked it! When the gas suffusing out from the nucleus gets hit by ultraviolet light it becomes ionized; one or more electrons get stripped off the atoms.

That's important because the Sun is blowing a wind of subatomic particles called the solar wind , and as it moves out from the Sun it carries a magnetic field with it. This field interacts with the comet's ions in the coma, shearing them away this process is pretty complicated, and not completely understood. As far as the solar wind cares, the comet is just standing still.

And that brings us to the comet's verdant glow. That green color is real, and not just from the way the picture was made! And it's the same reason a neon sign glows. Most of our information comes from studying the spectra of different comets. Scientists study the light reflected by different parts of a comet.

Gases contain different elements. Each element such as hydrogen , molecule such as water , or ion an electrically charged element or molecule has a distinct pattern of emission or absorption that can be determined in the laboratory; this pattern is known as its spectrum.

By matching patterns between laboratory measurements and comet observations, scientists can determine the composition of the comet. Every comet is made of the same basic ingredients — ice and dust. However, comets probably vary in how much of the ice is water ice and how much is ice made of other substances, such as methane, ammonia, and carbon dioxide. Comets also vary in the different types of trace elements and hydrocarbons are present.

Several space missions, such as the European Space Agency's Giotto mission, have explored comets and provided detailed imagery of comet surfaces. A few missions are intended to sample comets. NASA's Deep Impact mission will encounter Comet Tempel 1 in July , and will release a projectile into the comet surface to excavate a hole and expose a fresh surface on the nucleus. The spacecraft will collect data on comet emissions and will relay the data to scientists on Earth.

While the data from these missions will be from only a few comets and might not be representative, the data will greatly improve our understanding of comet compositions. What do the orbital paths of comets look like? Based on observations of how comets move through the sky, scientists have determined that comets travel around our Sun in highly elliptical oval-shaped orbits.

The time it takes to make a complete orbit is called a comet's period. Comet periods typically range from a few years to millions of years. Where do comets come from? Comets are divided into short-period comets and long-period comets. Short period comets — such as Comet Halley — revolve around our Sun in orbits that take less than years.

Their orbital paths are close to the same plane of orbit as Earth and the other planets, and they orbit our Sun in the same direction as the planets. Based on these orbital characteristics, short-period comets are believed to originate in the Kuiper belt , a disk-shaped region extending beyond Neptune. The Kuiper belt contains small, icy planetary bodies, only a few of which have been imaged.

Occasionally the orbit of a Kuiper belt object will be disturbed by the interactions of the giant planets in such a way that it will have a close encounter with Neptune and either be flung out of the solar system or pushed into an orbit within our solar system. Their orbital path is random in terms of direction and plane of orbit. Based on calculations from their observed paths, long-period comets are believed to originate in the Oort cloud.

The Oort cloud is a spherical envelope that may extend 30 trillion kilometers approximately 20 trillion miles beyond our Sun.

Oort cloud objects have never been imaged. As a comet approaches our Sun, it begins to heat up and the ice begins to sublimate — to change from a solid to a gas with no liquid stage.