Previous: Dwarf Planets Next: Asteroids. Comet Hyakutake Photographed by Peter Ceravolo. Comet Diagram click to enlarge. Back to top. Evolution of a Comet in its Orbital Path click to enlarge.
To see a comet in action, view the Orbit Simulator. This simulator shows the motion of the planets and other objects around the Sun. The Orbit Simulator click to launch. Explore how the sun affects comets and other orbiting bodies. The Solar Wind Tunnel click to launch. This is a composite of a short exposure image, taken to reveal the surface detail, overlain on a long exposure image which shows jets streaming out from the tremendously active surface click to enlarge.
A comet has no light of its own. We are able to see a comet because of the reflection of the Sun's light off of the comet and because of the gas molecules in the coma releasing energy absorbed from the Sun's rays. A Question As a comet approaches the Sun, does its head or tail lead the way? As it moves around from the Sun, which parts leads? Did you know? The Answer. Show me the Level 1 version of this page. A site for ages 14 and up.
Laura A. 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. Really, it is this interaction that I want to talk about. Important idea number 1: Matter is made of positive and negative charges. If you have anything with structure like dust particles then it has to have atoms in it. Basically, dust is made of a combination of electrons, protons and neutrons. That's it.
Important idea number 2: Light is an electromagnetic wave. What does this even mean? It can mean lots of things. For this discussion, the important thing is that if you have a region of space moving at the speed of light an electric and magnetic field can move in accordance with a set of rules we call Maxwell's equations.
Here is a typical representation of a sinusoidal EM wave from the awesome textbook Matter and Interactions. The electric field and magnetic field in this light must both be perpendicular to each other and to the direction the wave moves. That's important. Important idea number 3: If you have a charged particle in an electric field, it will experience a force.
For a positive charge, this force will be in the same direction as the electric field. For negative charges, the force is in the opposite direction as the electric field. In the above diagram, I am using the yellow arrows to represent a region with a constant electric field. The red ball is a positive charge and the blue is a negative charge. The red and blue arrows represent the forces on these charges. Important idea number 4: A moving electric charge will experience a force when moving in a magnetic field.
The force will be perpendicular to both the magnetic field and the direction the charge is moving. Just to make things a little bit more confusing, I am now using the yellow arrows to represent a magnetic field. In this diagram, the positive and negative charges are moving in opposite directions but both have a magnetic force in the same direction.
Yes, I used red arrows to represent both the velocity of the charge and the magnetic force. Maybe that was a bad idea. Here is a super short video demo of this magnetic force. The current in the wire is the same as a moving charge.
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